Interfacial Properties of Gold and Cobalt Oxyhydroxide in Plasmon-Mediated Oxygen Evolution Reaction

Water electrolysis is a green method of storing electrical energy in the chemical bonds of high-energy hydrogen gas (H₂). However, the anodic oxygen evolution reaction (OER) requires a significant kinetic overpotential, limiting the electrolysis rate. Recently, plasmonic gold nanoparticles (Au NPs) have been introduced to improve charge transfer at the interface between the OER electrocatalysts and the electrolyte under light illumination. Despite this, the mechanism by which Au NPs enhance photoassisted electrochemical processes remains poorly understood. To address this, we employed a model system comprising a plasmonic Au electrode and a cobalt (Co)-based electrocatalyst in alkaline electrolytes, studying the plasmon-mediated OER process through (photo)electrochemical and spectroscopic methods. Our findings revealed that a surfactant-free, electrodeposited plasmonic Au electrode could significantly enhance the electrocatalytic performance of Co-based OER electrocatalysts under continuous visible and near-infrared light illumination. Transient photocurrent studies showed that both the photothermal effect and energetic charge carriers contributed to the improved OER performance, with the Au|Co catalyst interface playing a key role in these enhancements. Additionally, electrochemical Raman measurements identified the active phase of the Co-based OER electrocatalyst to be cobalt oxyhydroxide (CoOOH) at oxidizing potentials.