Fe‐Doped Ni 3 S 2 Nanowires with Surface‐Restricted Oxidation Toward High‐Current‐Density Overall Water Splitting

Abstract It is critical to develop a highly effective and economical electrocatalyst to lower the energy losses for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, Fe‐doped Ni 3 S 2 nanowires with diameters of ca. 17 nm and lengths of 1.4∼2 μm are synthesized on Ni foam through a one‐step solvothermal route for alkaline water splitting, which display notable active and excellent durability for both OER and HER under high current densities. The optimal Fe 13.7% ‐Ni 3 S 2 nanowires electrode can attain 200 mA cm −2 at a fairly low overpotential of 223 mV, and 500 mA cm −2 at 245 mV toward OER. Furthermore, it yields a considerable low overpotential of 109 mV to garner 10 mA cm −2 , and 246 mV for 500 mA cm −2 toward HER. The incorporation of iron simultaneously modifies the electronic structure and morphology of Ni 3 S 2 , which not only enhances the conductivity but also generates abundant active edge sites. The slight surface‐restricted oxidation of nanowires in a strongly basic electrolyte in situ generates a large number of interfaces, which enables the reactivity and durability for both OER and HER. Accordingly, an alkaline water electrolyzer with two Fe 13.7% ‐Ni 3 S 2 electrodes only requires a low cell voltage of 1.53 V to achieve 10 mA cm −2 , and 1.95 V to 500 mA cm −2 with striking stability. The as‐prepared Fe‐doped Ni 3 S 2 nanowires can be potentially utilized for actual water electrolysis under high current densities.