Strategically Designed Efficient Electrode Material for Water Electrolysis Enabled by Synergistically Integrated Phosphide Heterostructure

ABSTRACT The intrinsically slow kinetics of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) continue to hinder the overall efficiency of the process, so the development of effective electrocatalysts is crucial for enabling electrochemical overall water splitting (OWS). In this study, we report a Mo ₂ Ni ₆ P ₃ ‐Ni ₂ P/NF heterostructured catalyst directly engineered on nickel foam (NF), featuring in situ generated nanoparticles uniformly anchored onto a nanorod framework. The catalyst is fabricated via a single‐step phosphorization of NiMoO ₄ /NF under an inert‐reductive atmosphere, forming a well‐interconnected bimetallic phosphide architecture. Benefiting from its synergistic heterostructure and conductive 3D scaffold, the catalyst delivers excellent OER and HER activity, requiring only 245 and 111 mV at 10 mA cm ⁻² . When used together as a two‐electrode electrolyzer, it allows OWS at the 50 mA current density and a cell voltage of just 1.70 V. Long‐term stability is confirmed through chronoamperometry, maintaining a steady operation at 20 mA cm ⁻² for 24 h without any noticeable degradation. The valence‐band XPS analysis reveals a tailored d‐band electronic structure in the hybrid phosphide system, facilitating optimized adsorption/desorption dynamics of the reaction intermediates and thereby boosting the catalytic performance. This work demonstrates a low‐cost, self‐supported transition‐metal phosphide electrocatalyst with strong potential for high‐efficiency water splitting.