Sulfur doped FeO nanosheet arrays supported on nickel foam for efficient alkaline seawater splitting

Developing economical, efficient and stable bifunctional catalysts for hydrogen production from seawater is of great significance for hydrogen utilization. Herein, sulfur doped iron oxide nanosheet arrays supported on nickel foam (FeO-Ni₃S₂@NF) are prepared by a one-pot solvothermal reaction. Owing to the high intrinsic activity of FeO-Ni₃S₂, the large catalytic specific surface area of nanosheet arrays and the fast charge transportation capability achieved by the self-supporting configuration, the FeO-Ni₃S₂@NF electrode delivers excellent catalytic performance in alkaline simulated seawater (1 M KOH + 0.5 M NaCl). Impressively, a low overpotential of 120 mV at 50 mA cm^-2 with a Tafel slope of 57 mV dec^-1 for the hydrogen evolution reaction and an overpotential of 470 mV at 200 mA cm^-2 with a Tafel slope of 62 mV dec^-1 for the oxygen evolution reaction are achieved. More importantly, the voltage is only 1.5 V at 50 mA cm^-2 for continuous overall water splitting for 100 h at 200 mA cm^-2 with negligible decay in alkaline simulated seawater with almost 100% Faraday efficiency. This work provides a simple and universal strategy to prepare highly efficient bifunctional catalytic materials, promoting the development of Earth-abundant materials to catalyse seawater splitting to produce high-purity hydrogen.