Phase reconstruction of Ni₂P/NiSe₂ heterostructure with co doping as bifunctional electrocatalyst for boosting overall water splitting

Designing efficient and low-cost bifunctional electrocatalysts is critical for advancing the practical application of water electrolysis for hydrogen production. Herein, we propose a dual modulation strategy to construct Co doped Ni₂P/NiSe₂ Heterogeneous electrocatalysts (Co-Ni₂P/NiSe₂) with staggered structure for boosting alkaline water splitting. Operando Raman spectroscopy was employed to monitor the evolution of active species, revealing that Co doping facilitates the phase transition of Co-Ni₂P/NiSe₂ from β-NiOOH to γ-NiOOH under operando electrochemical conditions. Density functional theory (DFT) calculations further clarify the origin of active site in Co-Ni₂P/NiSe₂, demonstrating that the Co site promotes the oxygen evolution reaction (OER), whereas the Co-Ni dual sites exhibit superior activity toward the hydrogen evolution reaction (HER). The reconstructed Co-Ni₂P/NiSe₂ exhibits a low overpotentials of 218 and 108 mV at 10 mA cm⁻² for OER and HER, respectively. Furthermore, the two-electrode electrolyzer needs a low cell voltage of 1.47 V at 10 mA cm⁻² and maintains exceptional durability for over 500 h at 100 mA cm⁻². This work presents a novel mechanistic insight into the design of promising bifunctional electrocatalyst.