Construction of hydrangea-like nanosheets with transition metal phosphide/phosphate heterostructure for boosting alkaline hydrogen evolution reaction activity.

Alkaline water electrolysis represents a viable technological approach for producing green H. However, the inherent low electrical conductivity and the hindrance in the hydrogen evolution reaction (HER) have led to slow kinetics of water splitting. Especially for the nickel‑iron layered double hydroxide (NiFe-LDH) catalyst loaded on nickel foam (NF), which is regarded as a potential alkaline HER catalyst. In this work, a phosphide/phosphate (NiP/(CoHPO)·3HO) heterostructure modified NiFe-LDH hydrogen evolution catalyst (NiP-CHPO/NiFe-LDH/NF) is designed by the hydrothermal-electrodeposition method. Benefiting from enhanced electron dynamics and abundant active sites, the hydrangea-like biomimetic structure of the NiP-CHPO/NiFe-LDH/NF catalyst exhibits outstanding HER catalytic activity. At 10 mA cm, the HER overpotential is 74 mV, and the catalyst exhibits excellent stability for 35 h. In-situ infrared spectroscopy analysis reveals that the optimized interfacial water structure of NiP-CHPO/NiFe-LDH/NF is the key factor for its enhanced performance. The density functional theory (DFT) calculations further confirm that the synergistic charge reconstruction effect of NiP-CHPO and the rapid H adsorption-desorption kinetics on the surface collectively contribute to the superior HER activity. This work demonstrates an efficient synthetic method for expanding the variety of phosphide/phosphate heterojunctions and provides new ideas for optimizing the hydrogen evolution efficiency of transition metal catalysts.