M (M=Mn, Fe, and Cu)-doped Ni3S2@Co9S8 grown on Ni foam with different heterostructures as catalysts for overall seawater splitting

The Mn-Ni 3 S 2 @Co 9 S 8 /NF electrode exhibits excellent hydrogen evolution reaction (HER) (overpotential of 76 mV @10 mA cm −2 ) and oxygen evolution reaction (OER) (overpotential of 261 mV @10 mA cm −2 ) activity in seawater electrolytes. • Mn-Ni 3 S 2 @Co 9 S 8 electrodes was synthesized for the first time through hydrothermal processes. • This Mn-Ni 3 S 2 @Co 9 S 8 /NF nanoarrays exhibits enhanced activity of the OER (overpotential of 261 m V @10 mA cm −2 ). • The synergistic effect of Co 3 S 4 and Mn-Ni 3 S 2 made electrode present superior hydrogen evolution performance. The increasing global energy demand and the environmental impact of fossil fuels have prompted scientists to seek clean and renewable energy solutions. Hydrogen energy, known for its efficiency and environmental benefits, is considered an ideal choice. Given the limited availability of freshwater resources, this study uses abundant seawater as the feedstock for water electrolysis. Our research focuses on developing non-precious metal electrocatalysts to enhance the efficiency and economic viability of water electrolysis for hydrogen production. Using Ni 3 S 2 @Co 9 S 8 as the base material, we regulate the catalytic performance by doping with transition metals such as Mn, Fe, and Cu. The Mn-Ni 3 S 2 @Co 9 S 8 /NF electrode exhibits excellent hydrogen evolution reaction (HER) (overpotential of 76 mV @10 mA cm −2 ) and oxygen evolution reaction (OER) (overpotential of 261 mV @10 mA cm −2 ) activity in seawater electrolytes, significantly reducing the overpotential requirements. Density Functional Theory (DFT) assessments reveal that Co 9 S 8 possesses optimal gibbs free energy capabilities and Mn-Ni 3 S 2 possesses more electron distribution, explaining its high catalytic efficiency. This study provides an in-depth analysis of the catalyst structure and performance, offering valuable insights for developing efficient and stable electrocatalysts for water electrolysis, thereby contributing to the sustainable development of the hydrogen economy and advancements in clean energy technology.