Electrochemical CO2 reduction reaction (eCO2RR) is performed on two intermetallic compounds formed by copper and gallium metals (CuGa2 and Cu9Ga4). Among them, CuGa2 selectively converts CO2 to methanol with remarkable Faradaic efficiency of 77.26% at an extremely low potential of −0.3 V vs RHE. The high performance of CuGa2 compared to Cu9Ga4 is driven by its unique 2D structure, which retains surface and subsurface oxide species (Ga2O3) even in the reduction atmosphere. The Ga2O3 species is mapped by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) techniques and electrochemical measurements. The eCO2RR selectivity to methanol are decreased at higher potential due to the lattice expansion caused by the reduction of the Ga2O3, which is probed by in situ XAFS, quasi in situ powder X-ray diffraction, and ex situ XPS measurements. The mechanism of the formation of methanol is visualized by in situ infrared (IR) spectroscopy and the source of the carbon of methanol at the molecular level is confirmed from the isotope-labeling experiments in presence of 13CO2. Finally, to minimize the mass transport limitations and improve the overall eCO2RR performance, a poly(tetrafluoroethylene)-based gas diffusion electrode is used in the flow cell configuration.

1. Structure-Tailored Surface Oxide on Cu-Ga Intermetallics Enhances
CO2 Reduction Selectivity to Methanol at Ultra-Low Potential
Debabrata Bagchi
Supervisor: Prof. Sebastian C. Peter
16th JNC Research Conference on Chemistry of Materials
(22/10/2022)

2. 2
The HadCRUT4 data set, 2014
Geoscientific model development discussions, 2016 climate.nasa.gov
Temperature increase
Temperature anomaly: 1.01 ºC
CO2 level
October, 2022: 415.62 ppm
Climate Challenge
CO2

3. 3
Electrochemical CO2 Reduction Reaction (ECO2RR)
Joule 2018, 2, 825-832
 Low CO2 solubility
 Large overpotential
 Poor selectivity
Challenges
Prof. T. Sargent,
University of Toronto
Bagchi, D.; Roy, S.; Sarma S. C.; and Peter, S. C., Adv. Funct. Mater. 2022, 2209023 (Review)
Competing hydrogen evolution reaction

4. Gas, ion, and electron meet
together
High performance
& high current
Limitation of Conventional Liquid phase ECO2RR
4
CO2
H+
H+
e-
Cathode
CO2 + m(H++ e-) CxHyOz + H2O
Anode
2H2O O2 + 4(H++ e-)

5. Gas phase ECO2RR in Flow cell
5
Flow Cell
Liquid phase
H-Cell
Gas phase
 Gas Diffusion
Electrode
-Porosity & Diffusion
-Roughness
-GDE (carbon/PTFE)
 Inherent
Parameters
-Catalyst design
-pH of electrolyte
-Potential
-Membrane
-Mass loading
-CO2 flow rate
-Electrolyte flow rate
 Flow Cell
Bagchi, D.; Sarkar, S.; Singh, A. K.; Vinod, C. P.; Peter, S. C., ACS Nano 2022, 16, 4, 6185–6196

6. Gas Diffusion Electrode for Higher Current
Carbon-based PTFE-based
Gas products
6
Liq. products

7. Top-Down approach of Cu-Ga Intermetallic Synthesis
Sample:Vulcan
(2:1)
30 cycle,
15 min for each cycle
@ 500 rpm
Mixture of Cu and Ga
in proper mole ratio
Cu-Ga phase diagram High-temperature synthesis
Ball milling process for bulk to nano
7
J. Phase Equilib. Diff. 2016, 37, 350-362

8. Structure of Cu-Ga Intermetallic Catalyst
CuGa2 Cu9Ga4
8
CuGa2 has pseudo 2D-type structure
promoting more active surface
Space Group : P4/mmm Space Group : P43m
_

9. Characterizations of Cu-Ga Intermetallic Catalyst
CuGa2 Cu9Ga4
9
CuGa2 Cu9Ga4
CuGa2
Cu9Ga4

10. ECO2RR performance and Faradaic Efficiency
10
CuGa2 Cu9Ga4
LSV
Higher methanol selectivity on CuGa2

11. Achieving Higher Current Density in Flow Cell
CuGa2 CuGa2
11
CuGa2
Stability
LSV

12. Local & Surface Electronic Structure Analysis
XAS Study XPS Study
XAS was performed at PETRA III, beamline P64, DESY, Germany XPS was performed at NCL, Pune in the collaboration with Dr. C. P. Vinod
12

13. Bagchi, D.; Roy, S.; Dheer, L.; Sarma, S. C.; Rajaji, V.; Narayana, C.; Waghmare, U. V.; Peter, S. C., Appl. Catal. B, 2021, 298, 20560
In-Situ Setup
Probing Active Site: In-Situ XAS Study
13
Ex-Situ In-Situ

14. In-Situ XAS study
XAS was performed at PETRA III, beamline P64, DESY, Germany 14
Surface
Gallium Oxide

15. In-Situ IR Experiment
Catal. Lett. 2005, 103, 83-88
ACS Energy Lett. 2019, 4, 682−689 15
Mechanism
In-Situ setup

16. Summary
16
Activity
Bagchi, D.; Raj, J.; Singh, A. K.; Cherevotan, A.; Roy, S.; Manoj, K. S.; Vinod, C. P.; C. Peter, S., Adv. Mater. 2022, 34, 2109426
Selectivity Higher
rate
Stability Mechanism Active site

17. Thank you…

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