Strong Electronic Interaction in Dual-Cation-Incorporated NiSe₂ Nanosheets with Lattice Distortion for Highly Efficient Overall Water Splitting

Exploring highly efficient and low-cost electrocatalysts for electrochemical water splitting is of importance for the conversion of intermediate energy. Herein, the synthesis of dual-cation (Fe, Co)-incorporated NiSe₂ nanosheets (Fe, Co-NiSe₂) and systematical investigation of their electrocatalytic performance for water splitting as a function of the composition are reported. The dual-cation incorporation can distort the lattice and induce stronger electronic interaction, leading to increased active site exposure and optimized adsorption energy of reaction intermediates compared to single-cation-doped or pure NiSe₂. As a result, the obtained Fe_0.09Co_0.13-NiSe₂ porous nanosheet electrode shows an optimized catalytic activity with a low overpotential of 251 mV for oxygen evolution reaction and 92 mV for hydrogen evolution reaction (both at 10 mA cm⁻² in 1 m KOH). When used as bifunctional electrodes for overall water splitting, the current density of 10 mA cm⁻² is achieved at a low cell voltage of 1.52 V. This work highlights the importance of dual-cation doping in enhancing the electrocatalyst performance of transition metal dichalcogenides.