Tunable NiSe‐Ni3Se2 Heterojunction for Energy‐Efficient Hydrogen Production by Coupling Urea Degradation

Abstract Urea‐assisted water splitting is a promising energy‐saving hydrogen (H 2 ) production technology. However, its practical application is hindered by the lack of high‐performance bifunctional catalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Herein, a heterostructured catalyst comprising highly active NiSe and Ni 3 Se 2 , along with a conductive graphene‐coated nickel foam skeleton (NiSe‐Ni 3 Se 2 /GNF) is reported. The heterostructured NiSe‐Ni 3 Se 2 originates from the in situ selenization of graphene‐coated nickel foam, allowing for careful regulation of the NiSe to Ni 3 Se 2 ratio by simply adjusting the calcination temperature. Theoretical calculations of the charge transfer between NiSe and Ni 3 Se 2 components can optimize the reaction pathways and reduce the corresponding energy barriers. Accordingly, the designed catalyst exhibits excellent UOR and HER activity and stability. Furthermore, the NiSe‐Ni 3 Se 2 /GNF‐based UOR‐HER electrolyzer requires only 1.54 V to achieve a current density of 50 mA cm −2 , which is lower than many recent reports and much lower than 1.83 V of NiSe‐Ni 3 Se 2 /GNF‐based OER‐HER electrolyzers. Moreover, the UOR‐HER electrolyzer exhibited negligible cell voltage variation during a 28‐h stability test, indicating satisfactory stability, which provides a new viable paradigm for energy‐saving H 2 production.