The incorporation of Bi into NiSe nanospheres accelerates Tafel recombination, enabling highly efficient water splitting

Abstract

In this study, a one-step co-electrodeposition method was employed to successfully introduce Bi into the NiSe system, resulting in the synthesis of a Ni₃Bi₂Se₂ bifunctional catalyst with an amorphous wrinkled nanosphere structure. This catalyst demonstrates exceptional electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), requiring low overpotentials of only 33 mV and 277 mV, respectively, at a current density of 10 mA cm⁻², along with remarkable stability over 120 hours. In the alkaline electrolyte, the overall water splitting reaction driven by this catalyst achieves a current density of 10 mA cm⁻² at a low cell voltage of 1.64 V. Theoretical calculations reveal that the incorporation of Bi significantly optimizes the Gibbs free energy (ΔG) of adsorption for H₂O molecules and reaction intermediates on the active sites of the metal selenide. Specifically, for the HER, the introduction of Bi brings the ΔG(H*) on Se sites close to zero, aligning with the Sabatier principle; for the OER, Bi doping effectively reduces the energy barrier of the rate-determining step (*O + OH⁻ → *OOH + e⁻), thereby accelerating the reaction kinetics. This study demonstrates that the doping strategy significantly enhances the electrochemical performance of transition metal compounds, providing new theoretical insights and practical approaches for designing highly efficient water-splitting catalysts.