The document provides an introduction to fuel cells, including:
1) A brief history of the first fuel cell invented in 1839.
2) Motivations for developing fuel cell technology such as limited fossil fuel resources and reducing CO2 emissions.
3) An overview of different types of fuel cells including PEMFC, AFC, PAFC, MCFC, and SOFC and their ideal efficiencies, applications, and current status.
The document provides an overview of fuel cell technology. It discusses the brief history of fuel cells and the basic principles of electrolysis and how fuel cells work by reversing the electrolysis process. It describes the main components of a fuel cell and the five most common types: alkaline, molten carbonate, phosphoric acid, proton exchange membrane, and solid oxide fuel cells. The benefits of fuel cells are highlighted such as efficiency, reliability and fuel flexibility. Challenges for different fuel cell types are also summarized, for example high operating temperatures of solid oxide fuel cells can limit applications.
The document discusses fuel cells, including:
1) A fuel cell generates electricity through an electrochemical reaction between a fuel (typically hydrogen) and oxygen, with water and heat as byproducts.
2) Fuel cells have several types but all consist of an anode, cathode, and electrolyte; they operate by separating the fuel from the oxygen to prevent combustion.
3) Applications include stationary power systems, transportation such as fuel cell vehicles and buses, and portable power devices, with each fuel cell type suited to certain uses.
This document discusses fuel cells, which are electrochemical devices that directly convert chemical energy from a fuel into electricity without combustion. It describes the basic components and principles of operation for various types of fuel cells, including proton exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and others. The document also covers advantages such as high efficiency and lack of emissions, as well as challenges like high costs and low service life. Applications discussed include vehicles, submarines, portable power, and spacecraft.
Electrolysis can be used to split water into hydrogen and oxygen gases. Fuel cells operate by reversing the electrolysis process, using hydrogen and oxygen to produce electricity and water. There are several types of fuel cells that differ in their electrolyte material and operating temperature, including proton exchange membrane fuel cells (PEMFCs), alkaline fuel cells (AFCs), phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), and solid oxide fuel cells (SOFCs). Fuel cells convert chemical energy directly into electrical energy and can use a variety of fuel sources.
Dinesh Mullangi Departmental seminar 12th August 2015mullangi dinesh
The document describes research into developing porous carbon-germanium nanoparticle composites for use as anode materials in lithium-ion batteries. Key points include:
- The composite, called 3D-Ge/C, was synthesized and shown through characterization to have a 3D nanostructure with large pore volume and surface area for lithium ion accessibility.
- Electrochemical testing found the material exhibited excellent performance as an anode, including high specific capacity close to the theoretical maximum, superior cyclability retaining 99.6% of capacity over 100 cycles, and ability to charge and discharge rapidly even at ultrahigh rates.
- When used in full cells paired with a lithium cobalt oxide cathode, the 3
A fuel cell converts hydrogen and oxygen into electricity, heat, and water through an electrochemical reaction. It has four main parts: an anode, cathode, catalyst, and proton exchange membrane. There are different types of fuel cells that use various electrolytes. Fuel cells have advantages like high efficiency, zero emissions, and quiet operation. Applications include stationary power sources, transportation, portable devices, and distributed power generation. Research continues to improve fuel cell performance and reduce costs.
Renewable Energy Technologies Course, chapter 2 hydrogen and fuel cellsProf . Ghada Amer
The document discusses different types of fuel cells, including solid oxide fuel cells (SOFCs) and molten carbonate fuel cells (MCFCs). SOFCs use a solid ceramic electrolyte and operate at very high temperatures of 800-1000°C. MCFCs use a molten carbonate salt suspended in a porous ceramic matrix as the electrolyte and operate at 650°C. Both fuel cell types allow hydrogen or other fuels to produce electricity through electrochemical reactions without combustion. While SOFCs and MCFCs offer high efficiency and fuel flexibility, their high operating temperatures also present challenges for applications and materials stability.
The document discusses green energy sources such as solar and wind power. It notes two main problems with fossil fuels: they are finite and will run out, and their combustion produces polluting gases. It then provides information on various green energy technologies like solar thermal power, photovoltaics, wind turbines, and their advantages and disadvantages. Key green energy sources discussed include solar power, which can be used for daylight, drying crops, heating spaces and water, and generating electricity via concentrated solar power or photovoltaics. Wind power is also summarized, including the power density of wind at different heights and applications of wind turbines.
The document provides an overview of fuel cell technology. It discusses the brief history of fuel cells and the basic principles of electrolysis and how fuel cells work by reversing the electrolysis process. It describes the main components of a fuel cell and the five most common types: alkaline, molten carbonate, phosphoric acid, proton exchange membrane, and solid oxide fuel cells. The benefits of fuel cells are highlighted such as efficiency, reliability and fuel flexibility. Challenges for different fuel cell types are also summarized, for example high operating temperatures of solid oxide fuel cells can limit applications.
The document discusses fuel cells, including:
1) A fuel cell generates electricity through an electrochemical reaction between a fuel (typically hydrogen) and oxygen, with water and heat as byproducts.
2) Fuel cells have several types but all consist of an anode, cathode, and electrolyte; they operate by separating the fuel from the oxygen to prevent combustion.
3) Applications include stationary power systems, transportation such as fuel cell vehicles and buses, and portable power devices, with each fuel cell type suited to certain uses.
This document discusses fuel cells, which are electrochemical devices that directly convert chemical energy from a fuel into electricity without combustion. It describes the basic components and principles of operation for various types of fuel cells, including proton exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and others. The document also covers advantages such as high efficiency and lack of emissions, as well as challenges like high costs and low service life. Applications discussed include vehicles, submarines, portable power, and spacecraft.
Electrolysis can be used to split water into hydrogen and oxygen gases. Fuel cells operate by reversing the electrolysis process, using hydrogen and oxygen to produce electricity and water. There are several types of fuel cells that differ in their electrolyte material and operating temperature, including proton exchange membrane fuel cells (PEMFCs), alkaline fuel cells (AFCs), phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), and solid oxide fuel cells (SOFCs). Fuel cells convert chemical energy directly into electrical energy and can use a variety of fuel sources.
Dinesh Mullangi Departmental seminar 12th August 2015mullangi dinesh
The document describes research into developing porous carbon-germanium nanoparticle composites for use as anode materials in lithium-ion batteries. Key points include:
- The composite, called 3D-Ge/C, was synthesized and shown through characterization to have a 3D nanostructure with large pore volume and surface area for lithium ion accessibility.
- Electrochemical testing found the material exhibited excellent performance as an anode, including high specific capacity close to the theoretical maximum, superior cyclability retaining 99.6% of capacity over 100 cycles, and ability to charge and discharge rapidly even at ultrahigh rates.
- When used in full cells paired with a lithium cobalt oxide cathode, the 3
A fuel cell converts hydrogen and oxygen into electricity, heat, and water through an electrochemical reaction. It has four main parts: an anode, cathode, catalyst, and proton exchange membrane. There are different types of fuel cells that use various electrolytes. Fuel cells have advantages like high efficiency, zero emissions, and quiet operation. Applications include stationary power sources, transportation, portable devices, and distributed power generation. Research continues to improve fuel cell performance and reduce costs.
Renewable Energy Technologies Course, chapter 2 hydrogen and fuel cellsProf . Ghada Amer
The document discusses different types of fuel cells, including solid oxide fuel cells (SOFCs) and molten carbonate fuel cells (MCFCs). SOFCs use a solid ceramic electrolyte and operate at very high temperatures of 800-1000°C. MCFCs use a molten carbonate salt suspended in a porous ceramic matrix as the electrolyte and operate at 650°C. Both fuel cell types allow hydrogen or other fuels to produce electricity through electrochemical reactions without combustion. While SOFCs and MCFCs offer high efficiency and fuel flexibility, their high operating temperatures also present challenges for applications and materials stability.
The document discusses green energy sources such as solar and wind power. It notes two main problems with fossil fuels: they are finite and will run out, and their combustion produces polluting gases. It then provides information on various green energy technologies like solar thermal power, photovoltaics, wind turbines, and their advantages and disadvantages. Key green energy sources discussed include solar power, which can be used for daylight, drying crops, heating spaces and water, and generating electricity via concentrated solar power or photovoltaics. Wind power is also summarized, including the power density of wind at different heights and applications of wind turbines.
A fuel cell converts chemical energy from a fuel into electricity through an electrochemical reaction. It requires a constant fuel source like hydrogen to continuously produce electricity. Fuel cells consist of an anode, cathode, and electrolyte. Protons flow from the anode to the cathode through the electrolyte, producing electricity. Fuel cells come in various types depending on the electrolyte used and stack together to increase voltage. They produce power efficiently but require a constant fuel source unlike batteries.
This document provides an overview of fuel cells, including:
1. Fuel cells convert chemical energy directly into electricity through electrochemical reactions. They can produce electricity continuously as long as fuel and oxygen are supplied.
2. Fuel cells are classified based on fuel/oxidizer type and electrolyte. Common types include hydrogen-oxygen, hydrocarbon, alkaline, phosphoric acid, and molten carbonate fuel cells.
3. Proton exchange membrane fuel cells (PEMFCs) operate at lower temperatures (50-100°C) and use a proton-conducting polymer membrane. They are being developed for transport and portable power applications.
I Hope You all like it very much. I wish it is beneficial for all of you and you can get enough knowledge from it. Clear and appropriate objectives, in terms of what the audience ought to feel, think, and do as a result of seeing the presentation. Objectives are realistic – and may be intermediate parts of a wider plan.
The document discusses energy storage components, specifically fuel cells. It provides an overview of fuel cells including their history, main issues, and the basic principles of hydrogen fuel cells. The basic chemical reaction of a fuel cell is presented. Different types of fuel cells are discussed based on their electrolyte, including proton exchange membrane fuel cells commonly used in vehicles. Fuel cell electrodes and their role in catalyzing the slow reaction rates are described. Thermodynamics and efficiency limits of fuel cells are briefly introduced.
The document discusses energy storage components, specifically fuel cells. It provides an overview of fuel cells including their history, main issues, and the basic principles of hydrogen fuel cells. The basic chemical reaction of a fuel cell is presented. Different types of fuel cells are discussed based on their electrolyte, including proton exchange membrane fuel cells commonly used in vehicles. Fuel cell electrodes and their role in catalyzing the slow reaction rates are described. Thermodynamics and efficiency limits of fuel cells are briefly introduced.
This study offers an overview of the technologies for hydrogen production especially alkaline water electrolysis using solar energy. Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. Alkaline water electrolysis is considered to be a basic technique for hydrogen production. In the present study, the effects of electrolyte concentration, solar insolation and space between the pair of electrodes on the amount of hydrogen produced and consequently on the overall electrolysis efficiency are experimentally investigated. The water electrolysis of potassium hydroxide aqueous solution was conducted under atmospheric pressure using stainless steel 316 as electrodes.
The experimental results showed that the performance of alkaline water electrolysis unit is dominated by operational parameters like the electrolyte concentration and the gap between the electrodes. Smaller gaps between the pair of electrodes and was demonstrated to produce higher rates of hydrogen at higher system efficiency
This study shows some attempts to product pure Hydrogen and pure Oxygen as both Hydrogen and Oxygen have there commercial demands.
This document summarizes an experiment investigating the behavior of a single fuel cell under different membrane electrode assemblies (MEAs) and fuels. Three MEAs using different catalysts were tested with hydrogen and formic acid as anode fuels and hydrogen, air, or water as cathode reactants. Constant base current with 10A pulses were applied to alleviate carbon monoxide poisoning on the anode. Results including polarization curves and potential/current oscillations are presented. The document also provides background on fuel cells and mechanisms of carbon monoxide poisoning.
This document discusses the use of nanotechnology in fuel cells. It provides a brief history of fuel cells and describes their basic components and mechanisms. It notes that nanotechnology can help address issues like using expensive catalyst materials and fuel storage. Specifically, carbon nanotubes can be used to store hydrogen fuel more easily and improve catalyst performance. Recent research is exploring catalysts that reduce or eliminate platinum usage. Fuel cells have applications in transportation, portable devices, and stationary power generation.
Fuel cells convert chemical energy directly into electrical energy through electrochemical reactions. They have various applications including powering vehicles, portable power and stationary power generation. There are several types of fuel cells classified based on electrolyte used such as PEMFC, DMFC, PAFC, MCFC and SOFC. Fuel cells have advantages like high efficiency, reliability and reduced emissions. However, fuel cells also have disadvantages like high manufacturing costs and lack of hydrogen infrastructure currently.
This document discusses various topics related to hydrogen as a transport fuel, batteries, and fuel cells. It provides information on:
- Different types of vehicles that use hydrogen or batteries as their fuel/power source
- Methods for producing and storing hydrogen
- How electrochemical cells like batteries and fuel cells work through redox reactions
- Characteristics and reactions of different types of batteries including lead-acid, nickel-cadmium, and lithium-ion batteries.
This presentation provides an overview of fuel cells, including their design, operation, types, advantages/disadvantages, and applications. It discusses how fuel cells work by electrochemically combining hydrogen and oxygen to produce electricity and water. The document outlines different classifications of fuel cells based on temperature, electrolyte, physical state of fuel used. It also compares fuel cells to batteries and internal combustion engines. Recent developments and applications of fuel cells in areas like transportation, power generation, and specialty uses are presented.
ENGINEERING CHEMISTRY- Solved Model question paper,2017-18rashmi m rashmi
This document contains the solved question paper for Engineering Chemistry. It discusses several topics:
1. The derivation of the Nernst equation for single electrode potential and its relationship to Gibbs free energy.
2. Concentration cells and calculating concentrations from cell potential.
3. The construction and working of a methanol-oxygen fuel cell.
4. The construction, working, and applications of lithium-ion batteries.
5. Key battery characteristics like cell potential, capacity, and cycle life.
6. The construction and advantages of a calomel reference electrode.
Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016chrisrobschu
There is a naval need for an air-independent advanced electric power source with high energy storage for unmanned undersea vehicles (UUV).
Current battery systems can not meet mission requirements.
Proton exchange membrane fuel cells (PEMFC) and solid oxide fuel cells (SOFC) are being investigated due to higher efficiencies and energy densities.
System safety must meet requirements for approval.
PEMFC and SOFC have been identified to meet UUV requirements due to their high efficiency and improved energy density over current battery systems.
Many options for reactant storage, critical for system energy.
System safety is critical for approval.
ONR BAA objectives to deliver TRL-6 fuel cell system for UUVs.
Fuel cells for uu vs 16_mar2016
Rechargeable Li-ion batteries based on Olivine-structured (LiFePO4) catho...Arun Kumar
The document provides an overview of rechargeable Li-ion batteries based on olivine-structured LiFePO4 cathode materials. It discusses the basics of batteries, emergence of lithium-ion rechargeable batteries, current status of cathode materials, and motivation for using LiFePO4. The experimental details cover synthesis of LiFePO4 nanoparticles via solid state route and various characterization techniques. Results from X-ray diffraction and Raman spectroscopy confirm the phase-pure orthorhombic structure of LiFePO4. Electrochemical characterization shows the improved conductivity and electrochemical performance of carbon-coated LiFePO4 nanoparticles.
Unit 06 - Fuel Cells, Hybrid power plant and Power factor improvementPremanandDesai
This document discusses fuel cells, hybrid power systems, and power factor improvement. It begins by defining fuel cells and describing their basic operation and classifications based on electrolyte, fuel/oxidant type, application, and other factors. It then discusses the working principles and specifications of specific fuel cell types like phosphoric acid, alkaline, and polymer electrolyte membrane fuel cells. Next, it covers hybrid power systems focusing on PV-diesel, PV-wind, and PV-fuel cell configurations. It concludes by explaining power factor, causes of low power factor, effects of low power factor, and various methods to improve power factor including static capacitors, synchronous condensers, and phase advancers.
This document discusses direct energy conversion through photovoltaic cells and fuel cells. It provides details on:
1) How photovoltaic cells convert solar energy into electrical energy through a module of approximately 30 cells producing around 15V and 1.5A of current. Applications include water pumping, commercial and residential power, and consumer electronics.
2) What fuel cells are, how they convert hydrogen and oxygen into water and electricity through electrochemical reactions. Types are classified by temperature and electrolyte used, with hydrogen-oxygen and fossil fuel cells discussed in detail.
3) Advantages of fuel cells include high efficiency and low emissions, while disadvantages include higher costs and difficulties with hydrogen production and storage.
Direct energy conversion (PV Cell, Fuel Cell)Ashish Bandewar
Direct Energy Conversion :- Photo voltage cells: Principle, concept of energy conversion, conversion efficiency, power output and performance, storage, Fuel Cells : Principles types of fuel cells, conversion efficiency
This document provides an overview of fuel cells, including their basic components and operation. It discusses how fuel cells work by separating hydrogen ions and electrons at the anode, with the electrons powering an external circuit before recombining with oxygen and ions at the cathode to form water. Two types of fuel cells are then described in more detail: phosphoric acid fuel cells, which were the first commercialized and use liquid phosphoric acid as the electrolyte, and alkaline fuel cells, which use an aqueous potassium hydroxide solution and react hydrogen and oxygen to produce water, heat and electricity.
Low power architecture of logic gates using adiabatic techniquesnooriasukmaningtyas
The growing significance of portable systems to limit power consumption in ultra-large-scale-integration chips of very high density, has recently led to rapid and inventive progresses in low-power design. The most effective technique is adiabatic logic circuit design in energy-efficient hardware. This paper presents two adiabatic approaches for the design of low power circuits, modified positive feedback adiabatic logic (modified PFAL) and the other is direct current diode based positive feedback adiabatic logic (DC-DB PFAL). Logic gates are the preliminary components in any digital circuit design. By improving the performance of basic gates, one can improvise the whole system performance. In this paper proposed circuit design of the low power architecture of OR/NOR, AND/NAND, and XOR/XNOR gates are presented using the said approaches and their results are analyzed for powerdissipation, delay, power-delay-product and rise time and compared with the other adiabatic techniques along with the conventional complementary metal oxide semiconductor (CMOS) designs reported in the literature. It has been found that the designs with DC-DB PFAL technique outperform with the percentage improvement of 65% for NOR gate and 7% for NAND gate and 34% for XNOR gate over the modified PFAL techniques at 10 MHz respectively.
A fuel cell converts chemical energy from a fuel into electricity through an electrochemical reaction. It requires a constant fuel source like hydrogen to continuously produce electricity. Fuel cells consist of an anode, cathode, and electrolyte. Protons flow from the anode to the cathode through the electrolyte, producing electricity. Fuel cells come in various types depending on the electrolyte used and stack together to increase voltage. They produce power efficiently but require a constant fuel source unlike batteries.
This document provides an overview of fuel cells, including:
1. Fuel cells convert chemical energy directly into electricity through electrochemical reactions. They can produce electricity continuously as long as fuel and oxygen are supplied.
2. Fuel cells are classified based on fuel/oxidizer type and electrolyte. Common types include hydrogen-oxygen, hydrocarbon, alkaline, phosphoric acid, and molten carbonate fuel cells.
3. Proton exchange membrane fuel cells (PEMFCs) operate at lower temperatures (50-100°C) and use a proton-conducting polymer membrane. They are being developed for transport and portable power applications.
I Hope You all like it very much. I wish it is beneficial for all of you and you can get enough knowledge from it. Clear and appropriate objectives, in terms of what the audience ought to feel, think, and do as a result of seeing the presentation. Objectives are realistic – and may be intermediate parts of a wider plan.
The document discusses energy storage components, specifically fuel cells. It provides an overview of fuel cells including their history, main issues, and the basic principles of hydrogen fuel cells. The basic chemical reaction of a fuel cell is presented. Different types of fuel cells are discussed based on their electrolyte, including proton exchange membrane fuel cells commonly used in vehicles. Fuel cell electrodes and their role in catalyzing the slow reaction rates are described. Thermodynamics and efficiency limits of fuel cells are briefly introduced.
The document discusses energy storage components, specifically fuel cells. It provides an overview of fuel cells including their history, main issues, and the basic principles of hydrogen fuel cells. The basic chemical reaction of a fuel cell is presented. Different types of fuel cells are discussed based on their electrolyte, including proton exchange membrane fuel cells commonly used in vehicles. Fuel cell electrodes and their role in catalyzing the slow reaction rates are described. Thermodynamics and efficiency limits of fuel cells are briefly introduced.
This study offers an overview of the technologies for hydrogen production especially alkaline water electrolysis using solar energy. Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. Alkaline water electrolysis is considered to be a basic technique for hydrogen production. In the present study, the effects of electrolyte concentration, solar insolation and space between the pair of electrodes on the amount of hydrogen produced and consequently on the overall electrolysis efficiency are experimentally investigated. The water electrolysis of potassium hydroxide aqueous solution was conducted under atmospheric pressure using stainless steel 316 as electrodes.
The experimental results showed that the performance of alkaline water electrolysis unit is dominated by operational parameters like the electrolyte concentration and the gap between the electrodes. Smaller gaps between the pair of electrodes and was demonstrated to produce higher rates of hydrogen at higher system efficiency
This study shows some attempts to product pure Hydrogen and pure Oxygen as both Hydrogen and Oxygen have there commercial demands.
This document summarizes an experiment investigating the behavior of a single fuel cell under different membrane electrode assemblies (MEAs) and fuels. Three MEAs using different catalysts were tested with hydrogen and formic acid as anode fuels and hydrogen, air, or water as cathode reactants. Constant base current with 10A pulses were applied to alleviate carbon monoxide poisoning on the anode. Results including polarization curves and potential/current oscillations are presented. The document also provides background on fuel cells and mechanisms of carbon monoxide poisoning.
This document discusses the use of nanotechnology in fuel cells. It provides a brief history of fuel cells and describes their basic components and mechanisms. It notes that nanotechnology can help address issues like using expensive catalyst materials and fuel storage. Specifically, carbon nanotubes can be used to store hydrogen fuel more easily and improve catalyst performance. Recent research is exploring catalysts that reduce or eliminate platinum usage. Fuel cells have applications in transportation, portable devices, and stationary power generation.
Fuel cells convert chemical energy directly into electrical energy through electrochemical reactions. They have various applications including powering vehicles, portable power and stationary power generation. There are several types of fuel cells classified based on electrolyte used such as PEMFC, DMFC, PAFC, MCFC and SOFC. Fuel cells have advantages like high efficiency, reliability and reduced emissions. However, fuel cells also have disadvantages like high manufacturing costs and lack of hydrogen infrastructure currently.
This document discusses various topics related to hydrogen as a transport fuel, batteries, and fuel cells. It provides information on:
- Different types of vehicles that use hydrogen or batteries as their fuel/power source
- Methods for producing and storing hydrogen
- How electrochemical cells like batteries and fuel cells work through redox reactions
- Characteristics and reactions of different types of batteries including lead-acid, nickel-cadmium, and lithium-ion batteries.
This presentation provides an overview of fuel cells, including their design, operation, types, advantages/disadvantages, and applications. It discusses how fuel cells work by electrochemically combining hydrogen and oxygen to produce electricity and water. The document outlines different classifications of fuel cells based on temperature, electrolyte, physical state of fuel used. It also compares fuel cells to batteries and internal combustion engines. Recent developments and applications of fuel cells in areas like transportation, power generation, and specialty uses are presented.
ENGINEERING CHEMISTRY- Solved Model question paper,2017-18rashmi m rashmi
This document contains the solved question paper for Engineering Chemistry. It discusses several topics:
1. The derivation of the Nernst equation for single electrode potential and its relationship to Gibbs free energy.
2. Concentration cells and calculating concentrations from cell potential.
3. The construction and working of a methanol-oxygen fuel cell.
4. The construction, working, and applications of lithium-ion batteries.
5. Key battery characteristics like cell potential, capacity, and cycle life.
6. The construction and advantages of a calomel reference electrode.
Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016chrisrobschu
There is a naval need for an air-independent advanced electric power source with high energy storage for unmanned undersea vehicles (UUV).
Current battery systems can not meet mission requirements.
Proton exchange membrane fuel cells (PEMFC) and solid oxide fuel cells (SOFC) are being investigated due to higher efficiencies and energy densities.
System safety must meet requirements for approval.
PEMFC and SOFC have been identified to meet UUV requirements due to their high efficiency and improved energy density over current battery systems.
Many options for reactant storage, critical for system energy.
System safety is critical for approval.
ONR BAA objectives to deliver TRL-6 fuel cell system for UUVs.
Fuel cells for uu vs 16_mar2016
Rechargeable Li-ion batteries based on Olivine-structured (LiFePO4) catho...Arun Kumar
The document provides an overview of rechargeable Li-ion batteries based on olivine-structured LiFePO4 cathode materials. It discusses the basics of batteries, emergence of lithium-ion rechargeable batteries, current status of cathode materials, and motivation for using LiFePO4. The experimental details cover synthesis of LiFePO4 nanoparticles via solid state route and various characterization techniques. Results from X-ray diffraction and Raman spectroscopy confirm the phase-pure orthorhombic structure of LiFePO4. Electrochemical characterization shows the improved conductivity and electrochemical performance of carbon-coated LiFePO4 nanoparticles.
Unit 06 - Fuel Cells, Hybrid power plant and Power factor improvementPremanandDesai
This document discusses fuel cells, hybrid power systems, and power factor improvement. It begins by defining fuel cells and describing their basic operation and classifications based on electrolyte, fuel/oxidant type, application, and other factors. It then discusses the working principles and specifications of specific fuel cell types like phosphoric acid, alkaline, and polymer electrolyte membrane fuel cells. Next, it covers hybrid power systems focusing on PV-diesel, PV-wind, and PV-fuel cell configurations. It concludes by explaining power factor, causes of low power factor, effects of low power factor, and various methods to improve power factor including static capacitors, synchronous condensers, and phase advancers.
This document discusses direct energy conversion through photovoltaic cells and fuel cells. It provides details on:
1) How photovoltaic cells convert solar energy into electrical energy through a module of approximately 30 cells producing around 15V and 1.5A of current. Applications include water pumping, commercial and residential power, and consumer electronics.
2) What fuel cells are, how they convert hydrogen and oxygen into water and electricity through electrochemical reactions. Types are classified by temperature and electrolyte used, with hydrogen-oxygen and fossil fuel cells discussed in detail.
3) Advantages of fuel cells include high efficiency and low emissions, while disadvantages include higher costs and difficulties with hydrogen production and storage.
Direct energy conversion (PV Cell, Fuel Cell)Ashish Bandewar
Direct Energy Conversion :- Photo voltage cells: Principle, concept of energy conversion, conversion efficiency, power output and performance, storage, Fuel Cells : Principles types of fuel cells, conversion efficiency
This document provides an overview of fuel cells, including their basic components and operation. It discusses how fuel cells work by separating hydrogen ions and electrons at the anode, with the electrons powering an external circuit before recombining with oxygen and ions at the cathode to form water. Two types of fuel cells are then described in more detail: phosphoric acid fuel cells, which were the first commercialized and use liquid phosphoric acid as the electrolyte, and alkaline fuel cells, which use an aqueous potassium hydroxide solution and react hydrogen and oxygen to produce water, heat and electricity.
Low power architecture of logic gates using adiabatic techniquesnooriasukmaningtyas
The growing significance of portable systems to limit power consumption in ultra-large-scale-integration chips of very high density, has recently led to rapid and inventive progresses in low-power design. The most effective technique is adiabatic logic circuit design in energy-efficient hardware. This paper presents two adiabatic approaches for the design of low power circuits, modified positive feedback adiabatic logic (modified PFAL) and the other is direct current diode based positive feedback adiabatic logic (DC-DB PFAL). Logic gates are the preliminary components in any digital circuit design. By improving the performance of basic gates, one can improvise the whole system performance. In this paper proposed circuit design of the low power architecture of OR/NOR, AND/NAND, and XOR/XNOR gates are presented using the said approaches and their results are analyzed for powerdissipation, delay, power-delay-product and rise time and compared with the other adiabatic techniques along with the conventional complementary metal oxide semiconductor (CMOS) designs reported in the literature. It has been found that the designs with DC-DB PFAL technique outperform with the percentage improvement of 65% for NOR gate and 7% for NAND gate and 34% for XNOR gate over the modified PFAL techniques at 10 MHz respectively.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
2. Contents
Contents
• Motivation
• Overview over different FC types
• Net reactions and ideal potentials (Nernst Equation)
• Actual performance and energy losses
• Atomistic view of electrodes
– Double layer models
– Potentials
– Capacity model
– Charge distribution
• Problems for fuel cell modeling:
– Electrode / Interface
– Membrane
– H2 storage
2
3. First Fuel Cell
First Fuel Cell
3
In 1839, William Grove, a British jurist and amateur physicist,
In 1839, William Grove, a British jurist and amateur physicist, first
first
discovered the principle of the fuel cell. Grove utilized four c
discovered the principle of the fuel cell. Grove utilized four cells,
ells,
each containing hydrogen and oxygen, to produce electric power
each containing hydrogen and oxygen, to produce electric power
which was then used to split the water in the smaller upper cell
which was then used to split the water in the smaller upper cell into
into
hydrogen and oxygen
hydrogen and oxygen
4. 4
Why Fuel Cells?
Why Fuel Cells?
• Limitation of
fossile energy
resources
• Increasing
CO2 emission
• Global warming
• Transport problems
• .....
5. Pros – Cons (Ideal Situation)
Pros – Cons (Ideal Situation)
+
• Direct energy conversion (no combustion)
• Low emissions
• No moving part in the energy converter
• Quiet
• High availability of lower temperature units
• Siting ability
• Fuel flexibility
• Remote/unattended operation
• Small size
—
• High market entry cost, production cost
• Unfamiliar technology to the power industry
• Almost no infrastructure
• Still at level of development
5
8. 8
Fuel Cell types
Fuel Cell types
η
η 50
50-
-65%
65% 50
50-
-80
80%
% 35
35-
-45%
45% 45
45-
-60%
60% 50
50-
-60%
60%
Applications
Applications Transport,
Transport,
space
space,
, ships
ships
transport
transport,
,cars
cars,
,
space
space,
,houses
houses,
,
ships
ships,mobile
,mobile
appl
appl.
.
100 MW
100 MW plants
plants
50
50-
-500 kW
500 kW
block
block heating
heating
plants
plants
100 MW
100 MW plants
plants
50
50-
-500 kW
500 kW
block
block heating
heating
plants
plants
100 MW
100 MW plants
plants
50
50-
-500 kW
500 kW
block
block heating
heating
plants
plants
Status quo
Status quo 50
50-
-100 kW,
100 kW,
can be bought
can be bought,
,
expensive
expensive
20 kW, high
20 kW, high
efficiency
efficiency
100 kW
100 kW
prototype
prototype
25 kW
25 kW prototype
prototype
9. Fuel Cell Overview
Fuel Cell Overview
9
Electrode
catalysis:
•Make more
efficient
•Reduce
overpotential
Electrolyte:
•Less expensive
•More efficient
•Wide operation
temperature range
H2 storage:
•Carbon Nanotubes
•Metal Hydrides
10. 10
Pros – Cons (specific)
Pros – Cons (specific)
•
• PEMFC:
PEMFC: + Solid electrolyte Æ excellent
resistance to gas crossover
– Low CO tolerance (~ppm level)
– low temperature
+ working temperature ~80C
Æ short startup time
– unefficient to use rejected heat
for cogeneration of additional
power
+ can work at high current
densities compared to other cells
– difficult heat and water
management limit the operating
power densities
CF2
CF2
CF CF2
O CF2
CF O CF2
CF2
SO3
x y
CF3
z H
Nafion
Nafion®
®
11. Pros – Cons (specific)
Pros – Cons (specific)
•
• AFC
AFC:
: + Excellent performance on H2 and
O2 compared to other cells due to
active O2 electrode kinetics
(70% efficiency)
+ relatively low temperatures
(~80C)
– very clean fuel required, since
small contaminations dissociate
alkaline base,
– CO2 poisoning
+ wide range of possible
electrocatalysts
– significant pressure difference
across the membrane is required
– large Pt quantity is needed
because of harsh conditions
11
ISS
ISS
KOH
KOH
in matrix
in matrix
Pt
Pt
Pt
Pt
12. Pros – Cons (specific)
Pros – Cons (specific)
•
• PAFC:
PAFC:
12
+ CO2 (of reformed fuel gas stream)
resistent electrolyte
– lower performance due to slow
cathode reaction (37-42%)
+ low working temperatures
(~200C)
+ water boiling point is not limiting
– fuel from external hydrocarbon
reformation
+ less complex fuel conversion
(no membrane and attendent
pressure drop)
– high cost catalysts
– harsh conditions
– CO poisoning
(water gas shift reaction required)
H
H3
3PO
PO4
4 Pt
Pt
Pt
Pt
Timesquare
Timesquare
13. 13
Pros – Cons (specific)
Pros – Cons (specific)
• MCFC : + higher temperatures (~650C)
less sensitive reactions and less
expensive materials
+ Ni as catalyst
– very corrosive and mobile
electrolyte
– source of CO2 is required at
cathode to form carbonate ions
+ reforming within the cell
+ CO can directly be used as fuel
+ heat exhaust can be used with
external gas turbine (η~80%)
– low sulfur tolerance
– high temperatures
(~650C)
– stainless steel as cell hardware
– complex working procedure
Li
Li2
2CO
CO3
3
K
K2
2CO
CO3
3
Ni
Ni
Ni
Ni
14. 14
Pros – Cons (specific)
Pros – Cons (specific)
• SOFC + ceramic construction
Æ no hardware corrosion
Æ no gas crossover due to
absence of liquid
+ fast kinetics
– incoming air has to preheated
– high temperature (~1000C)
Æ thermal expansion mismatch
Æ sealing between cells is
difficult
+ fast kinetics
+ CO is directly usable
+ no CO2 is required at cathode
(as in MCFC)
– constraints on material collection
– difficult fabricate process
– high electrical resistivity in the
electrolyte Æ low performance
+ high temperature (~1000C)
Æ fuel can be reformed within
the cell
– high cost catalysts
Anode: Ni
Anode: Ni
Cathode: LaMnO
Cathode: LaMnO3
3
Electrolyte: YSZ
Electrolyte: YSZ
ZrO
ZrO2
2[Y
[Y2
2O
O3
3]
]
18. Nernst Equation
Nernst Equation
Temperature
Temperature
dependence of H
dependence of H2
2/O
/O2
2
Ideal Potential
Ideal Potential
Ideal voltage (for oxidation of hydrogen) as a function of cell
Ideal voltage (for oxidation of hydrogen) as a function of cell temperature
temperature
18
20. Actual Performance
Actual Performance
20
•
•Concentration Polarization
Concentration Polarization Æ
Æ reactions reduce educt concentrations
reactions reduce educt concentrations η
ηconc
conc
•
•Activation Polarization
Activation Polarization Æ
Æ Rates of electrochemical reactions
Rates of electrochemical reactions η
ηact
act
•
•Ohmic Polarization
Ohmic Polarization Æ
Æ resistance of ion flow
resistance of ion flow η
ηohm
ohm
21. 21
Concentration Polarization
Concentration Polarization
Rate of mass transport to an electrode surface can be described
Rate of mass transport to an electrode surface can be described by Fick’s first law of
by Fick’s first law of
diffusion:
diffusion:
(
(D
D: diffusion coefficient,
: diffusion coefficient, c
ci
i: concentration,
: concentration, δ
δ: thickness of diffusion layer
: thickness of diffusion layer
The limiting current (
The limiting current (i
iL
L) is a measure of the maximum rate at which reactants can be
) is a measure of the maximum rate at which reactants can be
supplied to an electrode and occurs at
supplied to an electrode and occurs at c
csurface
surface=0:
=0:
Nernst equation for
Nernst equation for reactant species
reactant species at equilibrium is
at equilibrium is
When current flows
When current flows c
csurface
surface is less than
is less than c
cbulk
bulk and
and
Potential difference produced by a concentration change:
Potential difference produced by a concentration change:
22. 22
Activation Polarization
Activation Polarization
The activation polarization is customarily expressed by a semi
The activation polarization is customarily expressed by a semi-
-
empirical equation, called Tafel equation:
empirical equation, called Tafel equation:
Here
Here α
α is the electron transfer coefficient of the reaction at the
is the electron transfer coefficient of the reaction at the
electrode, and
electrode, and i
i0
0 is the exchange current density.
is the exchange current density.
The usual form is given by
The usual form is given by
where a = (
where a = (−
−2.3
2.3RT
RT/
/α
αν
νF)
F)·
·log
logi
i0
0 and b=
and b= 2.3
2.3RT
RT/
/αν
ανF.
F.
B is called the Tafel slope
B is called the Tafel slope
23. Actual Performance
Actual Performance
23
Sum of electrode polarization:
Sum of electrode polarization: η
ηanode
anode=
= η
ηact,a
act,a+
+ η
ηconc,a
conc,a
η
ηcathode
cathode=
= η
ηact,c
act,c+
+ η
ηconc,c
conc,c
The effect is to shift the potential of an electrode (
The effect is to shift the potential of an electrode (Φ
Φelectrode
electrode):
):
Φ
Φ’
’cathode
cathode=
= Φ
Φcathode
cathode −
− |
| η
ηcathode
cathode|
|
Φ
Φ’
’anode
anode=
= Φ
Φanode
anode + |
+ | η
ηanode
anode|
|
Φ
Φcell
cell=
= Φ
Φcathode
cathode − |
− | η
ηcathode
cathode| − (
| − (Φ
Φanode
anode + |
+ | η
ηanode
anode|) − I
|) − I·
·R
R
Φ
Φcell
cell=
=∆
∆Φ
Φ − |
− | η
ηcathode
cathode| − |
| − | η
ηanode
anode| − I·R
| − I·R
Φ
Φcell
cell= − |
= − | η
ηcathode
cathode| − |
| − | η
ηanode
anode| − I·R
| − I·R
Current flow reduces cell voltage due to electrode and ohmic pol
Current flow reduces cell voltage due to electrode and ohmic polarization
arization
Goal: Minimize the polarization
Goal: Minimize the polarization
25. Atomistic View of Electrode
Atomistic View of Electrode
Steps
Steps of
of electrochemical reaction
electrochemical reaction:
:
1.
1. Transport of
Transport of reactants
reactants to
to electrode
electrode
2.
2. Adsorption of
Adsorption of reactants
reactants at
at electrode
electrode (
(maybe dissociative ads
maybe dissociative ads.)
.)
e.g. H
e.g. H2
2 H
H2,
2,ads
ads; H
; H2,
2,ads
ads 2H
2Hads
ads; H
; H2
2 H
H+
+ + A
+ A–
–
3.
3. Electron transfer through phase boundary
Electron transfer through phase boundary
e.g. H
e.g. H+
+ + e
+ e–
– H
Hads
ads
4.
4. Follow
Follow-
-reactions
reactions at
at electrode
electrode surface and desorption
surface and desorption
e.g. 2H
e.g. 2Hads
ads H
H2
2(g)
(g)
5.
5. Removing reaction products
Removing reaction products to
to solution
solution
25
26. Electron Transfer
Electron Transfer
E
EF
F:
: Fermi
Fermi-
-level
level of metal
of metal
a
a: Tunnel distance
: Tunnel distance
Φ
Φ:
: Work function
Work function of metal
of metal
EA
EA:
: Electron affinity
Electron affinity
EA
EA >
> Φ
Φ for reduction
for reduction
Φ
Φ–
–EA
EA should be small
Metal
Metal
Electrolyte
Electrolyte
should be small
Open
Open circuit
circuit:
: Reaction takes place until equilibrium
Reaction takes place until equilibrium at
at electrode
electrode
equilibrium
equilibrium potential
potential φ
φ0
26
Opposite charge distribution
Opposite charge distribution
in metal and
in metal and electrolyte
0
electrolyte
27. Double-Layer
Double-Layer
Metal
Metal Electrolyte
Electrolyte (
(solution
solution)
)
x
x
solution
solution Electroneutral
Electroneutral!
!
Potential
Potential is
is a
a result
result of
of
the charge distribution
the charge distribution
27
•
•Equilibrium
Equilibrium:
: dynamic equilibrium
dynamic equilibrium of
of charge transfer
charge transfer in
in both
both
directions
directions of
of phase boundary
phase boundary
•
•Electrochemical process only if coupled with reduction
Electrochemical process only if coupled with reduction (
(oxidation
oxidation)
)
at
at opposite
opposite electrode
electrode
•
•open
open circuit
circuit: EMK =
: EMK = φ
φ0
0 of
of galvanic cell
galvanic cell
28. PSZ-Potential of Zero Charge
PSZ-Potential of Zero Charge
28
Negative
Negative
charging current
charging current
Positive
Positive
charging current
charging current
At a
At a certain electrode
certain electrode potential (potential of
potential (potential of zero
zero charge
charge)
) the
the
electrode
electrode surface
surface charge vanishes
charge vanishes:
: q
q = 0,
= 0, σ
σ = 0
= 0
This can be measured polarographically
This can be measured polarographically
measuring
measuring I
I for
for different
different φ
φ
I
I
29. Potential Convention
Potential Convention
29
ψ (outer potential)
χ
φ (inner potential)
Remove electrolyte without changing the charge distribution
Remove electrolyte without changing the charge distribution of
of the
the
metal (surface)
metal (surface)
1
1
2
2
3
3
Region 1: Test
Region 1: Test charge feels Coulomb
charge feels Coulomb potential at far
potential at far distances
distances
Region 2: Surface
Region 2: Surface charge is not
charge is not a point
a point charge
charge
Region 3: Test
Region 3: Test charge feels
charge feels surface
surface charges
charges
vacuum
vacuum
E
E
30. Detailed view of Double-Layer
Detailed view of Double-Layer
Physisorption
Physisorption:
:
-
- electrostatic interaction between
electrostatic interaction between
charges
charges
-
- charge
charge-
-dipol interaction
dipol interaction
-
- polarisation
polarisation of
of molecules
molecules and
and ions
ions
-
- dispersion forces
dispersion forces,
, vdW forces
vdW forces
-
- Attachment
Attachment of
of opposite charged
opposite charged
ions
ions and
and molecule
molecule-
-dipols
dipols
Chemisorption
Chemisorption:
:
-
- chemical interaction between
chemical interaction between
particles
particles and metal
and metal
30
31. Detailed view of Double-Layer
Detailed view of Double-Layer
31
Inner Helmholtz Plane:
Inner Helmholtz Plane:
plane of
plane of adsorbed species
adsorbed species
(
(direct electrode contact
direct electrode contact)
)
Inner Helmholtz
Inner Helmholtz Layer
Layer:
:
Area
Area of
of reactions with desolvated
reactions with desolvated
particles
particles
Outer
Outer Helmholtz Plane:
Helmholtz Plane:
plane of
plane of closest possible solvated
closest possible solvated
particles
particles
Outer Hemholtz Layer
Outer Hemholtz Layer:
:
Area
Area of
of redoxreaction between
redoxreaction between
solvated particles
solvated particles
32. Condensator Model of Double-Layer
o.H.p. model
Condensator Model of Double-Layer
o.H.p. model
32
Charge
Charge density
density on metal surface:
on metal surface:
equivalent charge density
equivalent charge density in o.H.p.
in o.H.p. Æ
Æ electric
electric double
double layer
layer
Integral double
Integral double layer capacity
layer capacity (relative to
(relative to psz level
psz level):
):
Differential double
Differential double layer capacity
layer capacity:
:
Measurement
Measurement of differential
of differential capacity with
capacity with DC
DC methods
methods,
, electrocapillar
electrocapillar-
-experiments
experiments
33. Condensator Model of Double-Layer
o.H.p. model
Condensator Model of Double-Layer
o.H.p. model
33
Double
Double layer capacity
layer capacity
Electrolyte resistance
Electrolyte resistance
Capacity
Capacity of
of
reference electrode
reference electrode
(
(usually neglected
usually neglected)
)
Measurement by
Measurement by potential drop
potential drop method
method:
:
Solving Diff
Solving Diff.
. Eq
Eq.
. for
for q,
q, then integrate over
then integrate over t:
t:
Evaluate
Evaluate I:
I:
34. Models for electric double layer
Models for electric double layer
34
Helmholtz (1853)
Helmholtz (1853)
static
static double
double layer
layer
Gouy
Gouy (1910) and
(1910) and
Chapman
Chapman (1913)
(1913)
diffuse double
diffuse double layer
layer
Stern (1924)
Stern (1924) static
static
and diffuse double
and diffuse double
layer
layer (
(combination
combination)
)
New
New model
model also
also include
include:
:
•
•Specific adsorption
Specific adsorption at
at electrode
electrode
•
•Ion
Ion-
-metal,
metal, molecule
molecule-
-metal
metal
interaction
interaction and
and catalytic effects
catalytic effects
•
•Structure
Structure of
of conduction bands
conduction bands
•
•Overlap between valence
Overlap between valence band and
band and
conduction
conduction band at
band at phase boundary
phase boundary
•
•Dielectric filling
Dielectric filling of double
of double layer
layer
•
•Deformation of
Deformation of conduction
conduction band
band
35. Stern Model
Stern Model
Double
Double layer without adsorption
layer without adsorption of
of ions
ions (
(charges
charges)
) within the
within the i.H.l.
i.H.l.
35
o.H.l.:
o.H.l.: static
static double
double layer
layer,
, free
free of
of charges
charges
Poisson equation with conditions
Poisson equation with conditions:
:
Zeta
Zeta-
-Potential at
Potential at the boundary between
the boundary between
static
static Helmholtz
Helmholtz layer
layer and diffuse
and diffuse layer
layer
Æ
Æ Distance
Distance-
-dependency
dependency of potential:
of potential:
Diffuse double
Diffuse double layer
layer:
: Electrolyte beyond the
Electrolyte beyond the o.H.l. (
o.H.l. (bulk solution
bulk solution)
)
Poisson equation
Poisson equation:
:
36. Stern Model
Stern Model
Diffuse double
Diffuse double layer
layer
36
Conditions
Conditions:
:
Boltzmann
Boltzmann-
-Ansatz
Ansatz for the charge
for the charge
distribution within the electrolyte
distribution within the electrolyte Insert into Poisson equation
Insert into Poisson equation:
:
If
If Æ
Æ small concentrations
small concentrations Æ
Æ Taylor
Taylor expansion
expansion
Solution of
Solution of the
the partial differential
partial differential equation
equation:
:
37. Stern Model
Stern Model
Diffuse double
Diffuse double layer
layer
37
Conditions
Conditions:
:
1. Condition:
1. Condition:
2. Condition:
2. Condition:
Debye
Debye-
-distance:
distance: κ
κ-
-1
1
center
center of
of charge
charge in
in the
the
diffuse double
diffuse double layer
layer
For x =
For x = κ
κ-
-1
1:
:
Charge
Charge-
-density
density
38. Stern Model
Stern Model
Diffuse double
Diffuse double layer
layer
Small
Small κ
κ Æ
Æ broad
broad double
double layer extends into electrolyte region
layer extends into electrolyte region
Æ
Æ ς
ς of
of the
the o.H.p.
o.H.p. can be replaced by the electrode
can be replaced by the electrode potential
potential
Electric
Electric Field
Field:
:
38
Continous transition
Continous transition at
at x
x =
= a
a:
:
Charge
Charge density as
density as a
a function
function of
of the electrolyte concentration
the electrolyte concentration and
and electrode
electrode potential:
potential:
39. Stern Model
Stern Model
Diffuse double
Diffuse double layer
layer
39
Low concentrations
Low concentrations:
: Potential
Potential-
-drop
drop within the
within the o.H.l.
o.H.l. is almost zero
is almost zero
High
High concentrations
concentrations:
:
Potential
Potential-
-drop
drop within the
within the o.H.l.
o.H.l. increases with increasing concentrations
increases with increasing concentrations,
, linearisation
linearisation
of
of Poisson equation may be critical
Poisson equation may be critical!
!
Charge of
Charge of the
the diffuse
diffuse layer
layer
Capacity
Capacity of
of static
static double
double layer
layer:
: Capacity
Capacity of diffuse double
of diffuse double layer
layer:
:
Plate condensator
Plate condensator at distance
at distance κ
κ
40. Problems
Problems for Fuel Cell
for Fuel Cell
Modeling
Modeling
Electrodes
Electrodes /
/ Interfaces
Interfaces
40
41. 41
Current problems for modeling I
Current problems for modeling I
•
• Morphology
Morphology of
of the catalyst
the catalyst
In order to
In order to provide
provide a
a large surface area for simultaneous catalysis
large surface area for simultaneous catalysis
Pt
Pt nanoparticles
nanoparticles are used instead
are used instead of (semi
of (semi-
-) infinite systems
) infinite systems
However
However:
:
–
– Nanoparticles have structural
Nanoparticles have structural and
and
electronical properties
electronical properties,
, which might
which might
strongly depend
strongly depend on
on size
size and
and shape
shape
(e.g. Quantum
(e.g. Quantum Size Effects
Size Effects)
)
–
– Nanoparticles combine
Nanoparticles combine a
a variety
variety of
of
different
different functional groups
functional groups: different
: different
surfaces
surfaces,
, steps
steps,
, kinks
kinks,
, tips
tips,
, vacancies
vacancies, ...),
, ...),
having
having different
different properties
properties
Eb=0.49eV Eb=1.10eV
42. Current problems for modeling II
Current problems for modeling II
42
•
• Influence
Influence of
of the support
the support
– Pt nanoparticles are attached to
larger Carbon particles (~50nm),
which will change their structures.
Smaller particles Æ less deformation, close to spherical
structure
Larger particles Æ strong deformation, ellipsoidal shape
– Pt nanoparticles are assumed to be 2-5nm in diameter.
However, due to relatively low diffusion
barriers agglomeration may occur to create
larger particles.
(again having modified properties)
– Supporting material:
Pd particles on Au have ~10 times
higher reactivity than Pd particles on Cu
43. Current problems for modeling III
Current problems for modeling III
43
•Bulk region should have
structural properties (density,
distribution, …) of bulk Nafion,
otherwise system need to be
expanded
•Water layer forms between
electrode and membrane
(will be different in presence of
E-field)
after 2ns
44. Current problems for modeling IV
Current problems for modeling IV
•
• Reactive
Reactive Environment
Environment
–
– Cathode
Cathode is
is surrounded
surrounded by
by a
a variety
variety of different
of different compounds
compounds:
:
•
• H
H2
2O of
O of the
the electrolyte
electrolyte, and
, and reaction
reaction product
product
•
• H
H3
3O
O+
+
as
as proton
proton carrier
carrier (
(surrounded
surrounded by
by water
water molecules
molecules)
)
•
• O
O2
2 gas as
gas as reaction
reaction component
component
•
• Different
Different reaction
reaction intermediates
intermediates
(e.g. O, H, OH, OOH, HOOH,...)
(e.g. O, H, OH, OOH, HOOH,...)
•
• Impurities
Impurities in
in the
the fuel
fuel (e.g. CO,
(e.g. CO, No
Nox
x, ...)
, ...)
Æ
ÆThe
The environment
environment might
might influence
influence the
the structure
structure,
, stability
stability, and
, and
composition
composition of
of the
the Pt
Pt nanoparticles
nanoparticles (
(or
or certain
certain functional
functional
groups
groups).
).
Æ
ÆThis
This may
may vary
vary for
for different
different T
T and
and p
p conditions
conditions
44
45. Current problems for modeling V
Current problems for modeling V
45
•
• Solvation
Solvation effects
effects due
due to solvent in
to solvent in the
the electrolyte
electrolyte
–
– In
In case
case of
of PEM
PEM-
-FCs
FCs the
the electrolyte
electrolyte is
is hydrated
hydrated
–
– At
At the
the cathode
cathode water
water is
is generated
generated
Æ
ÆThe
The electrode
electrode is
is surrounded
surrounded by
by water
water
molecules
molecules,
, which
which influence
influence adsorption
adsorption
energies
energies and
and structures
structures.
.
This
This might
might change
change the
the reaction
reaction
mechanism
mechanism,
, but
but also
also stabilize
stabilize or
or
destabilize
destabilize certain
certain structures
structures
(e.g.
(e.g. electrode
electrode,
, adsorbates
adsorbates)
)
Æ
ÆSolvation
Solvation can
can be
be treated
treated by
by a
a two
two-
- or
or
three
three-
-shell
shell model
model
46. Current problems for modeling VI
Current problems for modeling VI
46
•
• Electrode
Electrode potential
potential
–
– Besides
Besides T
T and
and p
p,
, the
the electrode
electrode potential
potential φ
φ is
is another
another parameter
parameter,
, which
which
influences
influences structures
structures and energetics
and energetics
Example
Example: Au(100)
: Au(100) surface
surface in 0.01M HClO
in 0.01M HClO4
4-
-solution
solution
φ
φ<0.25V quasi
<0.25V quasi-
-hexagonal
hexagonal reconstruction
reconstruction
φ
φ>0.25V
>0.25V unreconstructed
unreconstructed surface
surface (H.
(H. Ibach
Ibach et al., Surf.
et al., Surf. Sci
Sci. 375, 107
. 375, 107
(1997))
(1997))
–
– Distribution of negative and positive
Distribution of negative and positive
charges
charges within
within the
the solution
solution changes
changes
–
– Counter
Counter charges
charges will
will be
be on
on the
the surface
surface
of
of the
the metal
metal electrode
electrode
(
(whole
whole interface
interface is
is electroneutral
electroneutral)
)
Æ
Æ electric
electric double
double layer
layer establishes
establishes
Æ
Æ potential drop (
potential drop (strong
strong E
E-
-field
field) on
) on
the
the electrode
electrode surface
surface
47. Current problems for modeling VII
Current problems for modeling VII
•
• All
All previous
previous problems
problems deal
deal with
with the
the system in
system in equilibrium
equilibrium.
.
However
However,
, under
under steady
steady state
state conditions
conditions structures
structures,
, compositions
compositions, and
, and
reaction
reaction mechanisms
mechanisms might
might be
be significantly
significantly different?
different?
Æ
Æ Use
Use kinetic
kinetic simulations
simulations to
to study
study exactly
exactly these
these influences
influences.
.
However
However, in order to
, in order to get
get reliable
reliable results
results all
all significant
significant processes
processes should
should
be
be studied
studied and
and the
the corresponding
corresponding parameters
parameters extracted
extracted:
:
Adsorptions
Adsorptions,
, desorptions
desorptions,
, diffusions
diffusions,
, reactions
reactions, …
, …
47
49. Ions exert dielectric
friction on H+ mobility
Sensitive parameter for
conductivity and
permeation
Each level has
implications on
membrane
performance
Width of water domains
affected by electrostatic
repulsions and polymer
elasticity
Coarseness of the
surface affects viscous
movement of the ion
Connectivity of water
domains determines
transport
Mechanical properties of
the matrix
wate
r
polymer
Stochastic & Analytical
Modeling
Nafion Microstructure
Atomistic & Coarse Grain
Simulations
Nanosegregation
5 nm
3.5 nm 1 nm
Atomistic Simulations
Interface analysis
Hydrated Nafion is a
multiscale
heterogenous
material
SO
3
Nanostructure & Dynamics of Polyelectrolyte Membranes
Nanostructure & Dynamics of Polyelectrolyte Membranes
Rational approach to the study of PEM: experiments and simulation are
complementary
Backbone flexibility
Backbone hydrophobicity
Equivalent weight
Charge localization
Side chain flexibility
Side chain polarity
Confinement 49
Blockiness of polymer
Side chain length
Acidity of ionomer
Counter ion
Water content
Temperature
Architecture of side chain
Microphase segregation
Water diffusion
Mechanical properties
Water’s electroosmotic drag
Maximum water uptake
Water evaporation
Extent of ionomer solvation
Mechanism of gas diffusion
Counter ion migration
Hydronium transport
Patchiness of the water/PE
interface
Interfacial free volume
Degree of crystallinity
T of glass transition(s)
Water percolation
50. Membrane structure
Membrane structure
Nafion 117
CF2
CF2
CF CF2
O CF2
CF O CF2
CF2
SO3
x y
CF3
z M
50
=
ALTERNATED POLYMER
SMALL PATCHES
=
BLOCKY POLYMER
BIG SEGREGATED
PATCHES
Effect of polymer sequence
Blockiness affects the extent of nanophase
segregation (is better for the blocky polymer) and
water-polymer interface heterogeneity.
We compute a water percolation threshold that is in
agreement with the one inferred from conductivity
The percolation of the hydrophilic phase is
necessary for proton conductivity. 0
Edmondson et al.
Solid State Ionics
(2002)
152: 355-361
Effect of water content
All the ions of the polymer contact the water nanophase.
Water domain is far from spherical
Non perco. percolated
Non perco.
Water diffusion is ~25% faster in the more segregated
structure. Experimental results between blocky and random.
Vehicular diffusion of hydronium is comparable for both
sequences (no exp). Activation energies of water diffusion in
agreement with experiment.
51. Membrane characteristics
Membrane characteristics
Characteristics of water mobility in
Characteristics of water mobility in
(a) Pure water, (b) neutral and ionized nafion, (c)
(a) Pure water, (b) neutral and ionized nafion, (c)
hydrophobic slabs, (d) hydrophilic slabs, (e) neutral and
hydrophobic slabs, (d) hydrophilic slabs, (e) neutral and
ionized
ionized homogeneous solution
homogeneous solution of nafion fragments
of nafion fragments
(a) (b) (c) (d) (e)
51
53. Doped Carbon-Based Materials
Doped Carbon-Based Materials
MD/MC
MD/MC studies
studies:
:
3
4
5
6
7
8
6 7 8 9 10 11 12
Interlayer distance (Å)
H
ydrogen
uptaking
m
ass%
57
67
77
37
47
27
H
ydrogen
density
(kg/m3)
hydrogen density
mass%
50 bar
100 bar
100 bar
50 bar
target line
3.5
4.5
5.5
6.5
7.5
6 7 8 9 10 11 12
Inter-tube distance (Å)
Hydrogen
uptaking
mass%
62
72
52
32
42
Hydrogen
density
(kg/m3)
hydrogen density
mass%
50 bar
100bar
100 bar
50 bar
target line
53
W. Deng, W. A. Goddard
W. Deng, W. A. Goddard