Chromium leaching-induced electronic structure modulation in CoOOH for improved alcohol oxidation reactions

Abstract

Electrochemical benzyl alcohol (BA) oxidation in aqueous medium offers a promising approach to produce valuable chemicals at the anode, facilitating H₂ production at the cathode. Although the anodic oxidation of BA is thermodynamically favourable compared to the oxygen evolution reaction (OER), it also suffers from sluggish reaction kinetics, originating from multiple dehydrogenation steps. Hence, a low current density is achieved at a low potential, and the attempt to increase the current density at a higher potential leads to interference from the OER, reducing the faradaic efficiency (FE). To address these challenges, herein, we demonstrate a defect-rich cobalt oxyhydroxide (CoOOH-1) active catalyst, prepared by the electrochemical reconstruction of the CrCo-Prussian blue analogue (PBA) at the anode. During anodic activation, Cr was selectively leached out from the catalyst, generating a defect-rich structure having crystalline and amorphous domains. Most importantly, a drastic change in the electronic structure of the active catalyst was observed compared to CoOOH-2, derived from CoCo-PBA. CoOOH-1 with an optimised electronic structure, high electrochemical surface area, large number of active sites, and improved electronic conductivity produced superior electrocatalytic activity for both the OER and BA oxidation reaction. CoOOH-1 delivered an industrial-scale current density (400 mA cm⁻²) for BA oxidation at 1.53 V vs. RHE, far better than the other catalysts. Furthermore, a significant improvement (190 mV) in potential requirement was achieved by BA oxidation with CoOOH-1 compared to that of the OER. CoOOH-1 produced excellent FE (99%) with 100% selectivity for benzoic acid.