Unifying the ORR and OER with surface oxygen and extracting their intrinsic activities on platinum

• Published in: Nature communications Vol. 15; no. 1; pp. 7336 - 12
• Main Authors: Brandes, Benedikt Axel, Krishnan, Yogeshwaran, Buchauer, Fabian Luca, Hansen, Heine Anton, Hjelm, Johan
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 26.08.2024; Nature Publishing Group UK; Nature Portfolio
• Subjects: Cell surface; Chemical reactions; Comparative studies; Electrocatalysis; Electrolysis; Electrolytes; Electrons; Fuel cells; Hydrogen; Intermediates; Kinetics; Metal surfaces; Nanoparticles; Noble metals; Oxidation; Oxidation process; Oxygen; Oxygen atoms; Platinum; Reaction kinetics; Reduction (electrolytic)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-51605-1

Common half-cell measurements deliver oxygen reduction activities linked to the chosen scan rate, limiting their value for fundamental and comparative studies on platinum. Here we show a deconvolution of the intrinsic kinetics from the effect of surface oxygen on platinum. We find an electronic effect of the surface oxygen, substantiate a Tafel slope of ~120 mV/decade, obtain an exchange current density of 13 ± 4 µA/cm , and an activity of 7 mA/cm at 900 mV. Eventually, we broaden the scope of this analysis to the effects of surface rearrangement, alloying, and supported Pt nanoparticles, the latter providing insight into discrepancies between half-cell and fuel cell measurements. We find through computational methods that binding energies of intermediates would be weakened by the presence of highly coordinated oxygen atoms. Finally, we obtain a phenomenological rate equation for the oxygen reduction and evolution reaction, suggesting that both reactions follow a shared mechanism.