Basics & Future Directions of Photoelectrochemical splitting of water for hydrogen generation.

1. Photoelectrochemical Splitting of
Water for Solar Hydrogen Generation
Basics and Future Directions
Runjhun Dutta

2. Why Hydrogen?
 Energy Released:
140 kJ/g
 Heat of combustion
34.18 k Cal/g
 Energy storage capacity
119 kJ/mol
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Source: The Economist Technology, Quarterly, March 25, 2001. p. 29

3. Why PEC route for Hydrogen
generation?
 Based on solar energy, which is a perpetual
source of energy; and water, which is a
renewable resource.
 Environmentally safe, with no undesirable by
products.
 It may be used on both large and small scales.
Other routes for
Hydrogen
generation:
Wind
Tidal
Geothermal
Hydrothermal
Biological

4. PEC - Principle
Photoelectrochemical water decomposition is based on
the conversion of light energy into electricity within a
cell involving two electrodes, immersed in an aqueous
electrolyte, of which at least one is made of a
semiconductor exposed to light and able to absorb the
light. This electricity is then used for water electrolysis.
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5. Workingof PECcell
Electrons on
illumination travel
from VB to CB,
resulting in the
formation of holes in
the VB.
Electrons are transferred
to the counter electrode .
Holes react
with water
molecules
and oxidizes
it to release
oxygen and
protons.
Electrons react
with H+ ions and
reduce them to
hydrogen gas.
Photo-generation
and movement of
charge carriers in a
typical PEC cell

6. 6
For an alkaline electrolyte
For an acidic electrolyte
Tentative redox reactions in PEC water splitting
under acidic/alkaline conditions of electrolyte

7. “Performance Indicators
of a PEC cell
•Excitation of electrons in
photo-electrodes.
•Separation of charge carriers
•Electrode processes and
related charge transfers.
•Generation of the PEC voltage
required for water splitting.
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8. “
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Key factors affecting the
photoelectrochemical cell
activity
Size and shape of the nanoclusters
Electrolyte temperature
Electrolyte pH
Particle size and defects
Band gap energy
Intensity of light

9. 9
Schematic of the chemical stability of
materials used in an unbiased PEC cell

10. 10
DYE
SENSITIZATION
ION
IMPLANTATION
SWIFT HEAVY
ION
IRRADIATION
BILAYERED
SYSTEMS
MODIFICATION
TECHNIQUES
An overview of Surface/Bulk Modification
Strategies for enhanced PEC performance

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Effects of surface and interface
engineering on PEC water splitting

12. “Future Directions
•Development of efficient
materials/photoelectrodes.
•Optimization of synthesis route
for large-scale production.
•Integration of monolithic
devices and single cells into 2D
array/grid for mass-production
of H2.
•Evolution of safety standards.
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13. “In the Nutshell
•PEC water splitting is a technology
that is still taking shape.
•It is a technology for future, full of
hopes and promises; powered by
recent advances on material
science front and innovative
concepts of material design.
•A journey through dark tunnel,
surely with light at the end.
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14. Thank
You
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