MOF-Derived Formation of Ni₂P-CoP Bimetallic Phosphides with Strong Interfacial Effect toward Electrocatalytic Water Splitting

Bimetallic phosphides have attracted research interest for their synergistic effect and superior electrocatalytic activities for electrocatalytic water splitting. Herein, a MOF-derived phosphorization approach was developed to produce Ni₂P-CoP bimetallic phosphides as bifunctional electrocatalysts for both hydrogen and oxygen evolution reactions (HER and OER). Ni₂P-CoP shows superior electrocatalytic activities to both pure Ni₂P and CoP toward HER and OER, revealing a strong synergistic effect. High-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy elemental mapping analysis show that, in the sample Ni₂P-CoP, the Ni₂P and CoP nanoparticles with an average particle size 10-20 nm were mixed closely on the nanoscale, creating numerous Ni₂P/CoP interfaces. By comparison with the sample Ni₂P+CoP, in which seldom Ni₂P/CoP interfaces exist, we documented that the Ni₂P/CoP interface is an essential prerequisite to realize the synergistic effect and to achieve the enhanced electrocatalytic activities in Ni₂P-CoP bimetallic phosphides. This finding is meaningful for designing and developing bicomponent and even multicomponent electrocatalysts.