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

Abstract

Water-urea electrolysis represents a promising avenue for nitrogen removal and efficient green hydrogen production from ammonia nitrogen wastewater. However, a key challenge, viz., the lack of bifunctional electrocatalysts with exceptional activity and long-term current stability toward hydrogen evolution reaction (HER) and urea oxidation reaction (UOR), lies in this avenue. In this regard, a shell-shaped Ni₃S₂/NiMoP₂ heterostructure was constructed on nickel foam (NF) by a hydrothermal method coupled with the gas phase phosphating. Thanks to its laminated heterogeneous nanostructure with abundant oxygen vacancy and efficient electron mass transfer, this catalyst displays excellent activity both in HER and in UOR, with an ultra-low potential of −0.205 and 1.423 V (vs. RHE), respectively, to achieve a large current density of 1000 mA/cm². The dual-electrode water-urea system assembled with the bifunctional Ni₃S₂/NiMoP₂ catalyst requires only 1.580 V to achieve a current density of 500 mA/cm², which is 159 mV lower than that in the overall water splitting. Additionally, it exhibits great durability and can operate stably and continuously for up to 100 h under high current conditions.