Synergistic core-shell boosts P-CoNiMoO@CoP-NiP bifunctional catalyst for efficient and robust overall water splitting.

Optimizing hydrogen adsorption and enhancing water absorption are essential for the design of effective hydrogen evolution reaction (HER) electrocatalysts. Herein, a well-defined core-shell-structured P-CoNiMoO@CoP-NiP catalyst was synthesized on nickel foam via high-temperature phosphidation of heterostructured precursor CoMoO·xHO/NiMoO·xHO with hydrogen (H) assistance. This catalyst exhibits good HER performance, requiring only 24 mV of overpotential to achieve a current density of 10 mA cm, and long-term stability, maintaining a current density of 100 mA cm for over 100 h. Density functional theory calculations indicate that the molybdenum site is highly favorable for water adsorption in phosphorus-doped cobalt nickel molybdate (P-CoNiMoO), while the trigonal Ni site is optimal for hydrogen adsorption. These findings indicate that the cooperative interactions and functional division between the core and shell substantially enhance HER performance. In addition, P-CoNiMoO@CoP-NiP demonstrates high oxygen evolution reaction performance, achieving a current density of 10 mA cm at an overpotential of 243 mV. When functioning as a bifunctional electrocatalyst, it requires only 1.49 V to drive overall water splitting at a current density of 10 mA cm, with a durability of over 200 h at current densities of 100 and 300 mA cm. This study provides significant insights into the development of HER catalysts with potential applications in other fields.