Identification of Active Sites Formed on Cobalt Oxyhydroxide in Glucose Electrooxidation.

Transition-metal-based oxyhydroxides are efficient catalysts in biomass electrooxidation towards fossil-fuel-free production of valuable chemicals. However, identification of active sites remains elusive. Herein, using cobalt oxyhydroxide (CoOOH) as the archetype and the electrocatalyzed glucose oxidation reaction (GOR) as the model reaction, we track dynamic transformation of the electronic and atomic structure of the catalyst using a suite of operando and ex situ techniques. We reveal that two types of reducible Co 3+ -oxo species are afforded for the GOR, including adsorbed hydroxyl on Co 3+ ion (μ 1 -OH-Co 3+ ) and di-Co 3+ -bridged lattice oxygen (μ 2 -O-Co 3+ ). Moreover, theoretical calculations unveil that μ 1 -OH-Co 3+ is responsible for oxygenation, while μ 2 -O-Co 3+ mainly contributes to dehydrogenation, both as key oxidative steps in glucose-to-formate transformation. This work provides a framework for mechanistic understanding of the complex near-surface chemistry of metal oxyhydroxides in biomass electrorefining.