Immersion-Driven Structural Evolution of NiFeS Nanosheets for Efficient Water Splitting

The development of low-cost, highly active, and stable electrocatalytic water-splitting catalysts is crucial to solving the current energy crisis and environmental pollution. Herein, a simple two-step conversion strategy is proposed to successfully prepare NiFeS nanosheet structure catalyst through the "immersion-sulfurization" strategy. The self-supported electrode can be prepared in large quantities due to its simple preparation process. As an active substance, NiFeS can grow directly on the NiFe foam substrate, avoiding the use of adhesives or conductive agents, and directly used as electrodes. The as-obtained NiFeS/NFF-300 displays efficient catalytic activity in electrocatalytic water splitting. The overpotential required for OER of the NiFeS/NFF-300 electrode at a current density of 10 mA cm^-2 is 230 mV. The electrode underwent a stability test at 10 mA cm^-2 for 24 h, and the overpotential remained essentially unchanged, demonstrating excellent stability. Moreover, NiFeS/NFF-300 exhibits considerable HER performances compared with NiFeC₂O₄/NFF and NiFe foam. The unique nanosheet structure and the presence of Ni^δ+ and Ni²⁺ formed by NiFe foam substrate on the NiFeS surface are responsible for its excellent electrocatalytic activity.