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Insights into electrocatalysis
1Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106-7078, USA. aba@po.cwru.edu
Physical Chemistry Chemical Physics : PCCP
|December 14, 2011
Summary
This study calculates reversible potentials for oxygen reduction on platinum electrocatalysts, considering adsorption Gibbs energies. Effective reversible potentials are reduced by Gibbs energy loss, impacting oxygen reduction onset potentials.
Area of Science:
- Electrochemistry
- Surface Science
- Computational Materials Science
Background:
- Standard reversible potentials for bulk reactions are modified by reactant/product adsorption on electrocatalyst surfaces.
- Adsorption Gibbs energies (Δ(ads)G) are crucial for determining surface reversible potentials.
- Oxygen reduction reaction (ORR) intermediates' adsorption strengths influence overall reaction efficiency.
Purpose of the Study:
- To calculate reversible potentials for oxygen reduction steps on platinum electrocatalyst surfaces.
- To assess the accuracy of using adsorption Gibbs energies at the potential of zero charge.
- To determine the effective reversible potential for the four-electron ORR mechanism on platinum.
Main Methods:
- Utilized Interface 1.0 computational code to calculate potential-dependent electrochemical interfaces.
- Employed experimentally determined data for adsorption Gibbs energies of O, OH, and OOH intermediates.
- Calculated O-O bond dissociation Gibbs energies for key ORR intermediate steps.
Main Results:
- Reversible potentials for ORR on platinum were accurately benchmarked using Interface 1.0.
- Using Δ(ads)G at the potential of zero charge provides accuracy within ~0.1 V compared to bulk potentials.
- The OOH(ads) → O(ads) + OH(ads) step exhibits a ~1.2 eV exergonic Gibbs energy on platinum, reducing the effective reversible potential to ~0.93 V.
Conclusions:
- Adsorption Gibbs energies significantly influence surface reversible potentials for ORR.
- The effective reversible potential, not kinetics, dictates the onset potential for four-electron ORR.
- Calculations suggest the onset potential for ORR on Pt(111) equals its effective reversible potential.
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