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O: Fachverband Oberflächenphysik

O 67: Solid-Liquid Interfaces III: OER, ORR, CO2RR, etc.

O 67.5: Vortrag

Mittwoch, 18. März 2020, 11:45–12:00, WIL C107

Effect of electric field on oxygen reduction kinetics at the Pt(111), Au(111) and Au(100) electrodes — •Sara Kelly¹, Charlotte Kirk¹, Karen Chan², and Jens Nørskov² — ¹SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States — ²Department of Physics, Technical University of Denmark, Building 311, DK-2800 Lyngby, Denmark

Microkinetic modeling of the oxygen reduction reaction (ORR) has thus far failed to predict dependence of this reaction on pH on several important catalysts. In this work, we create a new microkinetic model for the ORR which incorporates field effects into the established computational hydrogen electrode (CHE) model. We find that field can significantly alter the binding energy of the ^*O₂, ^*OOH, and ^*H₂O₂ adsorbates. By considering these effects, we find that we can accurately reproduce experimental polarization curves and rotating ring disk electrode (RRDE) currents on Pt(111), Au(111), and Au(100) electrodes, allowing us to predict both overall ORR activity and selectivity toward hydrogen peroxide. We then use these predictions to better understand activity and selectivity of ORR catalysts and how each of these depends on pH. We show that hydrogen peroxide selectivity depends mainly on the binding energy of ^*H₂O₂ relative to that of ^*OOH. Finally, we argue that considering field effects can expand the search for improved ORR catalysts by allowing us to deconvolute the activity dependence of catalysts on the standard hydrogen electrode (SHE) and the reversible hydrogen electrode (RHE).