Yttrium- and nitrogen-doped NiCo phosphide nanosheets for high-efficiency water electrolysis

Engineering high-performance and low-cost bifunctional catalysts for H₂ (hydrogen evolution reaction [HER]) and O₂ (oxygen evolution reaction [OER]) evolution under industrial electrocatalytic conditions remains challenging. Here, for the first time, we use the stronger electronegativity of a rare-Earth yttrium ion (Y³⁺) to induce in situ NiCo-layered double-hydroxide nanosheets from NiCo foam (NCF) treated by a dielectric barrier discharge plasma NCF (PNCF), and then obtain nitrogen-doped YNiCo phosphide (N-YNiCoP/PNCF) after the phosphating process using radiofrequency plasma in nitrogen. The obtained N-YNiCoP/PNCF has a large specific surface area, rich heterointerfaces, and an optimized electronic structure, inducing high electrocatalytic activity in HER (331 mV vs. 2000 mA cm⁻²) and OER (464 mV vs. 2000 mA cm⁻²) reactions in 1 M KOH electrolyte. X-ray absorption spectroscopy and density functional theory quantum chemistry calculations reveal that the coordination number of CoNi decreased with the incorporation of Y atoms, which induce much shorter bonds of Ni and Co ions and promote long-term stability of N-YNiCoP in HER and OER under the simulated industrial conditions. Meanwhile, the CoN-YP₅ heterointerface formed by plasma N-doping is the active center for overall water splitting. This work expands the applications of rare-Earth elements in engineering bifunctional electrocatalysts and provides a new avenue for designing high-performance transition-metal-based catalysts in the renewable energy field.