Fabrication and Synergistic Effect Studying of Janus Ni2P/Ni5P4 Embedded in N-Doped Carbon as Efficient Electrocatalysts for Hydrogen Evolution Reaction
The integration of structural design and compositional modulation has been a hotspot for the optimization of electrocatalytic properties due to the synergistic effect. However, the details of synergistic effect still lack deep study. Herein, we fabricated a Ni2P/Ni5P4 electrocatalyst with Janus nanostructure through a controllable phosphidation approach. The as-obtained hybrid catalyst realized an overpotential of 104 mV and Tafel slope of 38.5 mV dec-1, which was smaller than the single Ni2P and Ni5P4, at a current density of -10 mA cm-2 in 0.5 M H2SO4 electrolyte. To revealed the reasons for the promotion of electrocatalytic properties, the synergistic effect was analyzed with the difference charge density (DCD), the density of state (DOS), ΔGH*, and the strength of internal electric field (IEF) on the interface between Ni5P4 and Ni2P. The results indicated that the composite structures could optimize the ΔGH* due to the change of DOS instead of DCD. Further calculations pointed out the composite structure could modify the effective electric field, which was often overlooked and might be the reason for the change of DOS. This study provided a new insight for designing multi-component catalysts and deeply illuminating a part of the synergistic effect for high-efficiently electrocatalytic activities.