Integrating Ni3N/Ni Gradient Heterostructure with Graphitized Carbon for Efficient Biomass Upgrading Coupled with H2 Production

The combination of biomass platform molecular oxidation with water electrolysis represents a promising strategy for low-energy hydrogen production and concurrent high-value chemicals generation. However, the practical implementation of this approach is still hindered by high overpotentials, inadequate selectivity, limited catalyst multifunctionality, and poor long-term stability. Herein, we developed a graphitized carbon-modified nickel nitride/nickel gradient heterostructure (C@Ni-N/Ni) synthesized through a facile strategy involving adsorption and subsequent high-temperature calcination. Experimental and theoretical results reveal that the constructed multi-interfacial structures (Ni3N/Ni, Ni3N/C, and Ni/C) with a gradient Ni distribution effectively optimize intermediate adsorption energies and facilitate the transition of low-valence nickel species (Ni0, Ni2+) to a higher valence state (Ni3+), thereby significantly accelerating the reaction kinetics of ethanol oxidation to acetate. Consequently, the integrated electrolysis system demonstrates remarkable performance, requiring only 1.44 V of cell voltage (without iR compensation) to achieve a current density of 10 mA·cm−2, while simultaneously delivering a high Faradaic efficiency of 91% for acetate production and exhibiting excellent stability. Furthermore, C@Ni-N/Ni gradient heterostructure also displays promising catalytic activity toward the electrooxidation of other small molecules, demonstrating its versatility. This study highlights a multi-interface coupled gradient engineering strategy for precise regulation of active sites, offering valuable insights for efficient biomass valorization and energy-saving hydrogen production.