Ammonia Etching to Generate Oxygen Vacancies on CuMn2O4 for Highly Efficient Electrocatalytic Oxidation of 5-Hydroxymethylfurfural

Electrocatalytic biomass valorization with renewable energy input represents a promising way to produce sustainable and non-fossil-based carbon products. The oxidative production of furandicarboxylic acid (FDCA) from bio-based 5-hydroxymethylfurfural (HMF) has attracted one of the most attention. Herein, spinel CuMn2O4 with an urchin-like nanostructure was synthesized by a hydrothermal method and subsequently soaked in ammonia water to create oxygen vacancies. The as-prepared material was used as an efficient electrocatalyst to oxidize HMF to FDCA. It was confirmed that CuMn2O4 etched with ammonia has an excellent electrocatalytic performance: at a current density of 20 mA/cm2, the potential of HMF oxidation was 1.31 V vs RHE in 1.0 M KOH solution with 10 mM HMF prior to the takeoff of the competing reaction, O2 evolution. Long-term chronoamperometry demonstrated that a 100% conversion of HMF and a 96% Faradaic efficiency of yield of FDCA were achieved. Our results indicated that it is feasible to employ the earth-abundant transition metal-based electrocatalyst CuMn2O4 to selectively oxidize biomass with higher energy conversion efficiency than water splitting as well as to produce valuable products in a H-type electrochemical cell.