Cobalt and Cerium\nDual-Doped Nickel Sulfide Nanostructures\nas a Bifunctional Catalyst for Overall Water Splitting

Developing efficient and cost-effective electrocatalysts\nfor both\nthe hydrogen evolution reaction (HER) and the oxygen evolution reaction\n(OER) is a pivotal challenge in harnessing hydrogen energy. Among\nthe promising candidates, transition metal sulfides have garnered\nsignificant research attention due to their low cost and exceptional\ncatalytic capabilities. In this work, we present a strategy to fabricate\nCo and Ce dual-doping Ni<sub>3</sub>S<sub>2</sub> nanosheets in situ\non nickel foam (CoCe-Ni<sub>3</sub>S<sub>2</sub>/NF) as an efficient\nand robust catalyst for overall water splitting. The introduction\nof Co and Ce dopants can induce an internal electronic interaction\nfor exposing more active sites and accelerating faster electron transfer.\nMeanwhile, the unique ultrathin two-dimensional (2D) nanosheet array\nnanostructure, with a thickness of 10 nm, facilitates enhanced electrolyte\ninfiltration and establishes efficient pathways for the release of\nH<sub>2</sub> and O<sub>2</sub> bubbles. Density functional theory\n(DFT) reveals that Co and Ce dual-doping can effectively optimize\nthe d-band center and improve the absorption energy of intermediates.\nThe synergy derived from these design features enables CoCe-Ni<sub>3</sub>S<sub>2</sub>/NF to exhibit a remarkable performance in both\nthe OER and the HER, as well as in overall water splitting. In 1.0\nM KOH electrolyte, this catalyst achieves impressive low overpotentials\nof 285 and 193 mV at 50 mA cm<sup>–2</sup> for the OER and\nHER, respectively. Notably, during overall water-splitting tests,\na potential of 1.68 V is achieved at 20 mA cm<sup>–2</sup>,\naccompanied by an outstanding durability for 100 h. These results\nunderscore the exceptional potential of CoCe-Ni<sub>3</sub>S<sub>2</sub>/NF as an efficient and robust catalyst for water splitting, paving\nthe way for advancements in sustainable hydrogen energy technologies.