Interfacial electronic structure modulation of Ni2P/Ni5P4 heterostructure nanosheets for enhanced pH-universal hydrogen evolution reaction performance

Transition-metal phosphides (TMPs) are regarded as the underlying substitutes to Pt-based catalysts for electrocatalytic hydrogen evolution reaction (HER), but the poor electrical conductivity and limited catalytic activity severely hinder its employment. Interface engineering is an available arrangement to enhance the catalytic activity of TMPs for HER process. The interface−engineered Ni2P/Ni5P4 heterostructure porous nanosheets was developed by a simple solvothermal method and a controllable low−temperature phosphorization treatment. Combining UPS characterization with DOS simulation, we disclose the existence of built-in electric field at interface region, and the electrons is transferred from Ni2P to Ni5P4 side. The DFT calculation results indicate that the active sites at interface domain possess the optimal H* adsorption free energy and lowest H2O dissociation energy barrier compared with single-phased Ni2P and Ni5P4, which is contributed to the electrons redistribution and electronic structure optimization, thereby enhancing the HER catalytic activity of Ni2P/Ni5P4 heterostructure nanosheets. The experimental results show it exhibits excellent HER performance in universal pH range. It merely requires the overpotentials of 78, 100, and 62 mV to achieve 10 mA/cm2 in 0.5 M H2SO4, 1 M PBS, and 1 M KOH electrolytes, respectively. Assembled with NiFeCH anode, we fabricated NiFeCH||Ni2P/Ni5P4 electrolyzer, which only needs the voltage of 1.52 V to achieve current density of 10 mA/cm2 in 1 M KOH. Even in complicated seawater system, the electrode and the electrolyzer still display outstanding electrocatalytic performance for hydrogen production. This report supplies an efficient strategy to enhance the electrolytic performance for hydrogen production from water splitting.