Electrochemical Hydrogen Peroxide Production on Single Atoms and Atomic Clusters

Abstract

The electrochemical oxygen reduction reaction (ORR) involving the transfer of two electrons (2-electron ORR) offers a sustainable alternative for the production of hydrogen peroxide (H2O2) on-site. Minimizing the use of expensive noble metal catalysts and maximizing their atomic utilization can be achieved by reducing the size of the catalysts. While previous studies have primarily focused on the relationship between particle size and oxygen reduction activity in the 4-electron ORR using Pt-based catalysts, less attention has been paid to the 2-electron ORR for H2O2 production. In this study, we prepared a series of size-controlled Pd clusters and investigated the oxygen reduction in acidic conditions to understand the relationship between cluster size and catalytic performance. Our results showed that larger Pd clusters favored the 4-electron ORR and the production of H2O, while smaller clusters favored the 2-electron ORR and the production of H2O2. To estimate the contribution of single atoms in the catalysts to their performance, we introduced CO. Using in-situ attenuated total reflection-surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS), we observed a range of CO vibrational signatures that correlated with specific ORR behaviors depending on the particle/cluster size.