Theoretical insights into the oxygen reduction reaction on PtCu (1 1 1): Effects of surface defect and acidic solvent

Abstract

Pt-metal alloys are widely reported catalysts for oxygen reduction reaction (ORR). However, their underlying catalytic reaction kinetics, particularly under catalyst surface defect and practical acidic conditions, have been rarely studied. In this work, ORR reaction kinetics on PtCu (111) are systematically studied using Density Functional Theory (DFT) analysis. Clean PtCu (111), defective PtCu (111)-DF and H atoms covered H-PtCu (111)-DF models were considered to investigate the effect of surface defects and H coverage on ORR reaction kinetics. In addition, the solvent effect (hydronium) was considered in this work to model a more realistic acidic reaction condition. The results show that defective PtCu (111)-DF surface is more active than clean PtCu (111), and ORR reaction proceeds with the peroxyl dissociation pathway on the two clean surfaces. However, when H coverage is considered on the PtCu (111)-DF surface, the ORR follows the oxygen dissociation pathway. Furthermore, when both H coverage and solvent effect were taken into consideration, the existence of hydronium can effectively facilitate the protonation of OH* and O* thus promoting the ORR reaction. The present study reveals that consideration of acidic conditions is essential in the study of ORR reaction mechanism and activity prediction for Pt-metal alloy catalysts.