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.