CoO-Co Heterojunction Covered with Carbon Enables Highly Efficient Integration of Hydrogen Evolution and 5-Hydroxymethylfurfural Oxidation

The renewable-energy-driven integration of hydrogen production and biomass conversion into value-added products is desirable for the current global energy transition, but still a challenge. Herein, carbon-coated CoO-Co heterojunction arrays were built on copper foam (CoO-Co@C/CF) by the carbothermal reduction to catalyze the hydrogen evolution reaction (HER) coupled with a 5-hydroxymethylfurfural electrooxidation reaction (HMFEOR). The electronic modulation induced by the CoO-Co heterojunction endows CoO-Co@C/CF with a powerful catalytic ability. CoOCo@C/CF is energetic for HER, yielding an overpotential of 69 mV at 10 mA center dot cm(-1) and Tafel slope of 58 mV center dot dec(-1). Meanwhile, CoO-Co@C/CF delivers an excellent electrochemical activity for the selective conversion from HMF into 2,5-furandicarboxylic acid (FDCA), achieving a conversion of 100%, FDCA yield of 99.4% and faradaic efficiency of 99.4% at the lower oxidation potential, along with an excellent cycling stability. The integrated CoO-Co@C/CF||CoO-Co@C/CF configuration actualizes the H2O-HMF-coupled electrolysis at a satisfactory cell voltage of 1.448 V at 10 mA center dot cm(-2). This work highlights the feasibility of engineering double active sites for the coupled electrolytic system.