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CO2 reduction on adatom decorated platinum stepped surfaces.
Intissar Kherbach1, Víctor Climent1, Juan M Feliu1
1Department of Physical Chemistry/Institute of Electrochemistry, University of Alicante, Apdo 99, E03080 Alicante, Spain.
The Journal of Chemical Physics
|June 1, 2023
Summary
CO2 reduction on platinum surfaces forms CO, with distinct mechanisms at high and low potentials. Step sites are crucial for CO formation, especially at higher potentials, and can be tuned with additives like copper.
Area of Science:
- Electrochemistry
- Surface Science
- Catalysis
Background:
- Understanding CO2 reduction is vital for sustainable energy technologies.
- Platinum (Pt) surfaces, particularly vicinal ones with steps, are key electrocatalysts.
- The roles of terrace versus step atoms in CO2 reduction remain incompletely understood.
Purpose of the Study:
- To investigate the mechanism of carbon monoxide (CO) formation from carbon dioxide (CO2) reduction on Pt(111) vicinal surfaces.
- To elucidate the distinct contributions of terrace and step sites in this electrochemical reaction.
- To explore the influence of selective step site modification (using Bi and Cu) on CO formation pathways.
Main Methods:
- Cyclic voltammetry was employed to study CO2 reduction kinetics.
- Selective modification of step sites on Pt(111) vicinal surfaces using bismuth (Bi) and copper (Cu) deposition.
- Analysis of reaction rates and product formation across different potential ranges (high and low potentials).
Main Results:
- Two mechanistic regimes were identified based on applied potential.
- At high potentials (0.2–0.4 V RHE), CO2 activation occurs at step sites, forming adsorbed CO. Bismuth decreased activity, while copper enhanced it.
- At low potentials (<0.2 V RHE), CO formation involves adsorbed hydrogen reacting with activated CO2 at step sites, with activity limited by hydrogen availability.
Conclusions:
- Step sites on Pt(111) vicinal surfaces play a critical role in CO2 electroreduction to CO.
- The reaction mechanism is potential-dependent, involving direct CO2 activation at steps (high potential) or reaction with adsorbed hydrogen (low potential).
- Surface modifiers like copper can enhance CO formation at step sites, offering a route for catalyst optimization.
