Shell-shaped Ni₃S₂/NiMoP₂ hetero-structure electrocatalyst for efficient water-urea electrolysis at high-current-density

Water-urea electrolysis represents a promising avenue for achieving nitrogen removal and efficient green hydrogen production in ammonia nitrogen wastewater. However, a key challenge lies in the lack of bifunctional electrocatalysts with exceptional catalytic performance and long-term current stability toward hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). In this regard, a shell-shaped Ni₃S₂/NiMoP₂ heterostructure was synthesized on nickel foam (NF) by hydrothermal coupled with gas phase phosphating method. Thanks to its laminated heterogeneous nanostructure, abundant oxygen vacancy, and efficient electron mass transfer, and displaying excellent catalytic activity in both HER and UOR. Achieving a large current density of 1000 mA/cm² requires ultra-low potentials of −0.205 and 1.423 V vs. RHE, respectively. In order to evaluate the practical application, the dual-electrode water-urea system assembled with bifunctional Ni₃S₂/NiMoP₂ requires only 1.580 V to achieve a current density of 500 mA/cm² simultaneously to boost HER and UOR, which is 159 mV lower than that in overall water splitting. Additionally, it exhibits strong durability under high current conditions, enduring stable and continuous operation for up to 100 h.