Promoted synergy in core-branch CoP@NiFe–OH nanohybrids for efficient electrochemical-/ photovoltage-driven overall water splitting

Developing low-cost, high-performance electrocatalysts to efficiently convert intermittent solar energy into hydrogen via water splitting is the key to realize sustainable energy cycle but remain challenges. Herein, the three dimensional core-branch CoP@NiFe–OH nanohybrids supported on surface-phosphatized Ni foam (CoP@NiFe–OH/SPNF) are facilely fabricated as the high-performance bifunctional electrocatalysts for alkaline water electrolysis. Theoretical calculation and electrochemical tests manifest that hybridizing CoP with NiFe–OH engenders strong synergistic catalytic effects, leading to fast hydrogen and oxygen evolution reaction kinetics. Meanwhile, hierarchical core-branch arrays and self-supported architecture also result in CoP@NiFe–OH/SPNF with multiple exposing active sites, faster ions, electron transport behavior and superior lifespan. Owing to these typical merits, the bifunctional CoP@NiFe–OH/SPNF electrode expedites overall water splitting with affording a current density of 10, 50 and 100 mA cm⁻² only at 1.53, 1.63 and 1.68 V respectively, surpassing the performance of noble (+)IrO₂/C//Pt/C(−) and most bifunctional electrocatalysts. As a practical application, a portable solar energy-driven water electrolyzer equipped with the bifunctional CoP@NiFe–OH/SPNF electrode can produce hydrogen at room temperature with a high gas evolution rate of 20.83 μL s⁻¹.