Synergism of electronic modulation and geometric architecture: bimetallic phosphide heterostructure on nickel foam for efficient water splitting

In the field of efficient and clean energy, significant challenges remain in constructing highly active bifunctional electrodes for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, two high-performance bifunctional electrodes with brush-like and wire-like cobalt/nickel phosphide heterostructure nanoarrays supported on nickel foam are constructed using a surface/interface reconstruction strategy, termed b-CoP/Ni₂P/NF, and w-CoP/Ni₂P/NF, respectively. The unique morphological configuration and rich heterostructure interface effectively accelerate the transformation of electrons and protons, exposing ultra-high active sites and carrier mobility. As a result, b-CoP/Ni₂P/NF, with its stronger proton/electron removal/insertion ability and higher conductivity, demonstrates remarkable electrocatalytic activity and kinetics in OER/HER processes. Moreover, the density functional theory calculations reveal that designing the construction of high-index surface heterojunctions can significantly optimize hydrogen adsorption energy in HER and reduce the intermediate (O* → OOH*) conversion barrier in OER. In practical applications, the b-CoP/Ni₂P/NF achieves a very low overpotential and excellent stability in alkaline double-electrode full-cell water-splitting systems.