Beyond Platinum: Defects Abundant CoP₃/Ni₂P Heterostructure for Hydrogen Evolution Electrocatalysis

Water electrolysis is a promising option for pure hydrogen production, but it is limited by the high cost. Developing superb and low-cost electrocatalysts for hydrogen evolution reaction (HER) is critical for cost reduction. Heterostructures are demonstrated with excellent HER activities, but still inferior to commercial Pt/C. Herein, vacancy type of defects is engineered into the interface of CoP₃/Ni₂P heterostructure by a plasma strategy. The as-synthesized defective CoP₃/Ni₂P exhibits lower overpotentials than Pt/C. Its specific activity at overpotential of 50 mV is ≈2-fold and 1.7-fold higher than that of Pt/C in acidic and alkaline media, respectively. For water electrocatalysis, its current density reaches 215 mA cm^-2 at 2.0 V, even satisfying the target of practical industrial water splitting. Theoretical calculations indicate that the interfacial defects reconstruct the electronic structure and accelerate the charge transfer, facilitating the adsorption of reactant and lowering the energy barrier of water dissociation, thereby improving HER activities.