Transition metal atom doped Ni3S2 as efficient bifunctional electrocatalysts for overall water splitting: Design strategy from DFT studies

Exploring stable, inexpensive and highly active bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a long-desired topic in the area of sustainable and renewable energy sources. Herein, ten kinds of transition metal (TM = Mn, Fe, Co, Cu, Mo, Ru, Rh, Pd, Ir and Pt) were doped in Ni3S2 matrix to design TM-Ni3S2 candidates, and their catalytic activities for overall water splitting were systematically explored based on density functional theory. Our results demonstrated that doping TM atoms is an effective tactic to boost the catalytic activity of Ni3S2 matrix. Among these candidates, Mn-Ni3S2, Fe-Ni3S2, and Ru-Ni3S2 exhibit the outstanding catalytic activity for water splitting, with the much lower overpotentials being just 0.02/0.29 V, 0.11/0.29 V and 0.01/0.33 V for HER/OER, respectively, which are equivalent to or even superior to the prevailing bifunctional catalysts. Particularly, d-band center was employed to reveal the origin of OER activity. Our findings may open up new routes for the design of advanced Ni3S2-based catalysts for water splitting and realize the wide-range applications of Ni3S2-based catalysts in fields of clean and renewable energy.