Atomic Heterointerface Engineering of Ni₂P-NiSe₂ Nanosheets Coupled ZnP-Based Arrays for High-Efficiency Solar-Assisted Water Splitting

In this study, heterogeneous nickel phosphide-nickel selenide (Ni₂P-NiSe₂) nanosheets are constructed to coat zinc phosphide-based nanorods (ZnP NRs) under a unique core@shell architecture, which acts as a highly active multifunctional catalyst toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The catalyst exhibits an overpotential of 79 mV at 10 mA cm^–2 for HER and 326 mV at 100 mA cm^–2 for OER in freshwater under an alkaline condition. The formation of an open 3D channel architecture derived from highly conductive ZnP@Ni₂P-NiSe₂ nanorods attached nickel foam generates more exposed active sites and promotes fast mass transport. In addition, density functional theory study reveals a synergistic effect between Ni₂P and NiSe₂ phase to reduce adsorption free energy and increase the electronic conductivity, thereby accelerating the catalytic reaction kinetics. An electrolyzer of the ZnP@Ni₂P-NiSe_2(+,-) requires only cell voltages of 1.54 V (1.43 V) and 1.51 V (1.44 V) to deliver 10 mA cm^–2 in freshwater and mimic seawater at 25 °C (75 °C), respectively, along with prospective long-term stability. Furthermore, the solar energy-assisted water splitting process demonstrates a solar-to-hydrogen efficiency of 19.75%, implying that the catalyst is an effective and low-cost candidate for water splitting.