Carbon-based nanoarrays embedded with Ce-doped ultrasmall Co2P nanoparticles enable efficient electrooxidation of 5-hydroxymethylfurfural coupled with hydrogen production

The electrooxidation of 5-hydroxymethylfurfural (HMFOR) not only offers a green route to attain high-value 2,5-furandicarboxylic acid (FDCA) from biomass, but also is considered as a promising approach to replace the kinetically sluggish OER for future hydrogen production. Herein, we report the construction and structural optimization of Ce-doped ultrasmall Co2P nanoparticles (NPs) in carbon-based nanoarrays to boost HER-coupled HMFOR. We demonstrate that the electronic structure of Co-based electrocatalysts can be positively regulated by Ce doping and the optimized Ce-Co2P-based electrocatalyst only require a low voltage of 1.20 V vs. RHE to achieve 10 mA cm(-2) for HMFOR with an excellent FDCA Faraday efficiency (FEFDCA) of 98.5%, which are superior to its Ce-free counterpart (1.29 V vs. RHE; FEFDCA=83.9 %). When being assembled into a HER-coupled HMFOR system, this bifunctional electrocatalyst can achieve 50 mA cm(-2) with an ultralow voltage of 1.46 V, which is reduced by 210 mV as compared with that of its Ce-free counterpart (1.67 V). Quasi-operando experiments and DFT calculations further reveal the significant roles of Ce doping in promoting the charge transfer between active sites and HMF, and reducing the free energy barrier of intermediate (*HMFCA) dehydrogenation. This study provides new insights into the underlying mechanisms of Ce doping into metal phosphides for boosting HER-coupled HMFOR, developing a facile methodology to construct efficient electrocatalysts for energy storage/conversion systems.