Electronic structure regulation and polysulfide bonding of Co-doped (Ni, Fe)1+xS enable highly efficient and stable electrocatalytic overall water splitting

The durability of electrocatalysts is comparably as important as the efficiency for practical applications. Transition metal sulfides usually undergo phase evolution during the oxygen evolution reaction (OER), making the resulting electrocatalysts unstable. Here we report the synthesis of Co-doped (Ni, Fe)1+xS (denoted as FeCoNiS), and that its derived electrocatalyst exhibited remarkably high OER activity and excellent stability with an overpotential of 164 mV for 10 mA cm−2 and a steady-state current density of 100 mA cm−2 for up to 2200 h. The impressive OER performance can be attributed to the electronic structure regulation of (Ni, Fe)1+xS via Co doping and the formation of polysulfides (Sn2−). Promisingly, a device assembled using FeCoNiS and MoNi4/MoO2 two-electrodes delivered a current density of 100 mA cm−2 at a low potential of 1.60 V for overall water splitting and worked stably for 1200 h at a current density of 200 mA cm−2. This work provides a new strategy to explore transition metal sulfides as efficient and stable catalysts for large-scale hydrogen production.