Highly efficient electrooxidation of 5-hydroxymethylfurfural (HMF) by Cu regulated Co carbonate hydroxides boosting hydrogen evolution reaction

The biomass electrochemical oxidation has attracted worldwide attention owning to its carbon-neutral and sustainable nature. Here, different morphologies of CoCu-carbonate hydroxides (CH) electrodes are prepared through one-step hydrothermal method for 5-hydroxymethylfurfural electrocatalytic oxidation (HMF-ECO) to high-valued 2,5-furandicarboxylic acid (FDCA) for the first time. The results illustrate that Cu can regulate CoCu–CH morphologies from 1D nanorods to 2D ultra-thin nanosheets besides modulating the catalytic compositions. The optimal Co1Cu1–CH exhibits hybrid nanostructures containing the 1D nanorods and 2D ultra-thin nanosheets, which has the largest ECSA and specific surface area, as well as the smallest Tafel slope and impedance. The oxidation potential of HMF-ECO is 1.42 V vs RHE with the conversion of HMF 99.57%, the selectivity for FDCA 99.91%, and the FE 98.88%. In addition, Cu can promote the conversion of Co2+ to the favorable Co3+ for HMF-ECO on the catalyst surface. Density functional theory calculation indicates that Cu can improve charges transfer to HMF and lower its adsorption energy. In situ Raman spectra tests indicate that cobalt species is the active site for HMF-ECO. Furthermore, at 1.42 V vs RHE, the coupling of HMF-ECO and hydrogen evolution reaction shows that the cathodic hydrogen evolution rate is 92.33 L h−1 m−2, which is 3.69 times more than water splitting. This work provides a special structures material to process intensification of HMF electrooxidation coupling hydrogen production.