Cobalt and Cerium Dual-Doped Nickel Sulfide Nanostructures as a Bifunctional Catalyst for Overall Water Splitting

Developing efficient and cost-effective electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is a pivotal challenge in harnessing hydrogen energy. Among the promising candidates, transition metal sulfides have garnered significant research attention due to their low cost and exceptional catalytic capabilities. In this work, we present a strategy to fabricate Co and Ce dual-doping Ni₃S₂ nanosheets in situ on nickel foam (CoCe-Ni₃S₂/NF) as an efficient and robust catalyst for overall water splitting. The introduction of Co and Ce dopants can induce an internal electronic interaction for exposing more active sites and accelerating faster electron transfer. Meanwhile, the unique ultrathin two-dimensional (2D) nanosheet array nanostructure, with a thickness of 10 nm, facilitates enhanced electrolyte infiltration and establishes efficient pathways for the release of H₂ and O₂ bubbles. Density functional theory (DFT) reveals that Co and Ce dual-doping can effectively optimize the d-band center and improve the absorption energy of intermediates. The synergy derived from these design features enables CoCe-Ni₃S₂/NF to exhibit a remarkable performance in both the OER and the HER, as well as in overall water splitting. In 1.0 M KOH electrolyte, this catalyst achieves impressive low overpotentials of 285 and 193 mV at 50 mA cm^-2 for the OER and HER, respectively. Notably, during overall water-splitting tests, a potential of 1.68 V is achieved at 20 mA cm^-2, accompanied by an outstanding durability for 100 h. These results underscore the exceptional potential of CoCe-Ni₃S₂/NF as an efficient and robust catalyst for water splitting, paving the way for advancements in sustainable hydrogen energy technologies.