Elucidating Electrocatalytic Oxygen Reduction Kinetics via Intermediates by Time Resolved Electrochemiluminescence

Abstract

Rapid and accurate evaluation of oxygen reduction reaction (ORR) kinetics for massive potential electrocatalysts is critical for developing sustainable energy conversion devices. In principle, both the consumption rate of O2 and production rate of reactive oxygen radicals (ROS) intermediates can be used to establish the ORR rate equation. Notably, owing to the grand challenge in quantitative in-situ detection of trace-amount of ROS, most previous ORR kinetics studies rely on direct electrochemical examination of O2 consumption, but which is inevitably hampered by the slow mass transfer of O2 in electrolytes. Here we report a time resolved electrochemiluminescence (Tr-ECL) strategy to establish ORR rate equation via ultra-sensitive detection of ROS intermediates. As ROS were generated at electrocatalysts surfaces in the diffusion layer, it intrinsically circumvented the limit of mass transfer of O2 in electrolytes during ORR. As a result, ORR electron transfer numbers, rate constants, and ROS concentration-potential correlations that is closely related to the stability of electrocatalysts were successfully obtained by principal component analysis of ECL intensities and finite elemental analysis of time-resolved ECL decay curves. It provides a rapidly, precisely, and facile way to understand ORR mechanism and would greatly pave development of electrocatalysts with appropriate catalytic activity, selectivity and stability.