Modulating Oxygen Defects in Co3O4 via Electrochemical Reduction for Efficient 5-Hydroxymethylfurfural Electrooxidation

Electrochemical oxidation of 5-hydroxymethylfurfural (HMF) is an environmentally friendly and economical method to produce valuable 2,5-furandicarboxylic acid (FDCA). While great efforts have been devoted to developing non-noble-metal electrocatalysts for the HMF electrooxidation reaction (HMFOR), the activity still needs to be improved. Herein, taking Co3O4 as the model electrocatalyst, we demonstrate oxygen defect engineering as an effective method to enhance the HMFOR activity. Various concentrations of oxygen vacancies are introduced into Co3O4 by electrochemical reduction. The HMFOR performance exhibits a volcano dependence on the concentration of oxygen vacancies. Under the optimal reduction condition of −1.8 V (vs Hg/HgO) and 5 min, the HMF conversion rate and faradaic efficiency of FDCA are enhanced by 3.7- and 2-fold, respectively. Theoretical calculations further demonstrate that the presence of oxygen vacancies promotes the adsorption of HMF and decreases the reaction energy barriers during HMFOR. Our results provide critical insight into the role of oxygen defects in determining the HMFOR activity, and the method can be applied to the synthesis of highly active electrocatalysts for the electrochemical oxidation reactions of other biomasses.