Hydrochar-Supported Bimetallic Ni–Cu Nanocatalysts for Sustainable H₂ Production

Noble-metal-free heterometallic Ni–Cu nanoparticles (NPs) supported on hydrochar have been developed for CO2 sorption-enhanced steam reforming of acetic acid (AC) to enhance H2 production. Among all noble-metal-free heterometallic nanoparticles catalysts, the catalyst with a Ni:Cu molar ratio of 6:4 displayed the best catalytic performance in AC steam reforming with exceptional 95% of H2 concentration. The electronic structure change and interfacial interaction between metal NPs and hydrochar surface as a function of Ni:Cu molar ratio were elucidated by multiple techniques. The electronic transitions in the metal–hydrochar interface could be effectively modulated by thermal treatment or adjusting the molar ratio of metal precursors. Moreover, the redox-active moieties (e.g., quinones and hydroquinones) on hydrochar surface were found to not only facilitate the interaction of metal–support but also endow the metal NPs with extraordinary electronic properties via the formation of conjugated metal–carbon bonds. This work provided a unique, effective synthetic platform for the facile self-assembly functionalization and engineering of noble-metal-free heterometallic NP catalysts with alloy structures. This strategy could be exploited for exact manipulation of properties and applications of more complicated metal nanoparticles via the interfacial modification of the hydrothermal carbon through the formation of diverse metal–nonmetal bonds.