In Situ Synthesis of Mn-Doped CoP@Ni2P Nanoneedles as a High-Performance Bifunctional Electrocatalyst for Efficient Water Splitting

The development of efficient and low-cost bifunctional electrocatalysts for overall water splitting is crucial for sustainable hydrogen production. In this work, we report the in situ synthesis of Mn-doped CoP@Ni ₂ P nanoneedle arrays supported on nickel foam as a high-performance electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The catalyst is composed of vertically aligned nanoneedles, which provide abundant active sites and facilitate charge transfer. Benefiting from the electronic modulation induced by Mn doping and the synergistic effect of the CoP@Ni ₂ P heterostructure, the optimized Mn-CoP@Ni ₂ P electrode exhibits exceptional catalytic activity, delivering low overpotentials of 61.7 mV for the HER and 122.0 mV for the OER at 10 mA cm ^-2 in 1.0 M KOH. Impedance and relaxation-time analyses reveal faster and more homogeneous interfacial electron transfer after Mn incorporation. Furthermore, systematic measurements across acidic and alkaline electrolytes demonstrate stable catalytic responses over a wide pH range, indicating that the heterostructure effectively accommodates proton- and hydroxide-mediated reaction pathways. Moreover, when employed as both the anode and the cathode in a two-electrode electrolyzer, the assembled device only requires a cell voltage of 1.48 V to deliver a current density of 10 mA cm ^-2 . This work provides a promising strategy for the design of non-precious metal electrocatalysts with optimized performance for efficient overall water splitting.