Probing the relationship between bulk and local environments to understand impacts on electrocatalytic oxygen reduction reaction

Local catalyst environments fluctuate during electrochemical reactions which significantly influences reaction efficiency and selectivity. However, elucidating fundamental relationships between local envi-ronment and electrocatalytic performance is challenging due to the difficulty in probing this local region. Here, we study the impact of electrolyte composition on the kinetics and mechanism of the oxygen reduction reaction (ORR) for a carbon catalyst. Using a rotating ring-disk electrode equipped with an irid-ium oxide pH probe, we monitor changes in local pH during ORR. We confirm that local pH changes sig-nificantly for near-neutral bulk pH and find that different cations provide variable pH-buffering, thereby modulating overall magnitude and onset of local pH changes. Overall, local pH more strongly dictates changes in mechanisms and performance, while the cation identity modulates local pH to influence these trends. This work highlights the importance relating local pH to electrocatalytic performance to further improve understanding of complex electrochemical processes.(c) 2022 Elsevier Inc. All rights reserved.

Automated summary

This study investigates the impact of electrolyte composition on the kinetics and mechanism of the oxygen reduction reaction (ORR) by monitoring local pH changes. The results demonstrate that local pH strongly dictates changes in mechanisms and performance, while the cation identity modulates local pH to influence these trends.