Localized Phosphorization Synthesis of Vacancy-Rich NiCo₂O₄/NiCoP Urchin-like Heterojunction for Alkaline Electrocatalytic Water Splitting

The rational construction and targeted fabrication of highly active transition metal spinel oxides-based bifunctional electrocatalysts is of great significance for achieving efficient water splitting performance, but challenges still remain. Herein, we have successfully developed an attractive bifunctional electrocatalyst of vacancy-rich NiCo2O4/NiCoP urchin-like heterojunction (P-NiCo2O4-V) by plasma bombardment and subsequent localized phosphorization for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The engineered P-NiCo2O4-V not only possesses a porous spherical nanoskeleton, beneficial nanowire array surface morphology, abundant oxygen vacancies, and multiple active components but also displays significant heterointerface interactions. Consequently, in alkaline electrolyte, P-NiCo2O4-V demonstrates exceptional bifunctional electrocatalytic performance, achieving extremely low overpotentials of 159 mV (HER) and 280 mV (OER) at 10 mA cm–2, with Tafel slopes of 90 and 67 mV dec–1, respectively. Moreover, the P-NiCo2O4-V requires only 1.64 V to deliver 10 mA cm–2 for overall water splitting in a two-electrode electrolyzer and maintains 90% stability within 10 h. Most importantly, the vacancy and interface engineering integration strategies explored in this study offer a fresh perspective for the development of efficient OER and HER bifunctional electrocatalysts.