Electrochemical glucose-to-formic acid conversion coupled with alkaline hydrogen production over nanostructured CuCo2O4 catalysts

Abstract

Coupling the hydrogen evolution reaction (HER) with the electrochemical oxidation of glucose (GOR), one of the most abundant biomass-based platform molecules, could be a promising approach to reduce the energy consumption of hydrogen production, while also producing value-added chemicals powered by renewable energy. However, it remains difficult to develop an efficient electrocatalyst with high activity and low costs for GOR. Herein, we introduce a serious of earth-abundant elements into the Co₃O₄ spinel nanostructure to use as electrocatalysts for GOR. The optimized CuCo₂O₄ spinel oxide nanoneedles exhibit excellent GOR electrocatalytic activity, which only requires 1.31/1.40 V vs. reversible hydrogen electrode (RHE) to achieve the high current densities of 200/500 mA cm⁻², obtaining a high 98% faradaic efficiency of formate at 1.40 V vs. RHE. The high performance is attributed to the abundant oxygen vacancies and transient formation of CoOOH active species on the surface of CuCo₂O₄ and rapid consumption by the spontaneous chemical reaction with glucose, which are evidenced by in situ Raman spectroscopic measurements and electrochemical tests. The two-electrode electrolytic cell voltage of GOR coupled with HER is about 370 mV lower than that of overall water electrolysis at 200 mA cm⁻².