A multiphase nickel iron sulfide hybrid electrode for highly active oxygen evolution

Development of highly active electrocatalysts for oxygen evolution reaction (OER) is one of the critical issues for water splitting, and most reported catalysts operate at overpotentials above 190 mV. Here we present a multiphase nickel iron sulfide (MPS) hybrid electrode with a hierarchical structure of iron doped NiS and Ni3S2, possessing a benchmark OER activity in alkaline media with a potential as low as 1.33 V (vs. reversible hydrogen electrode) to drive an OER current density of 10 mA cm(-2). The Fe doped NiS, combined with highly conductive disulfide phase on porous Ni foam, is believed to be responsible for the ultrahigh activity. Further more, density functional theory simulation reveals that partially oxidized sulfur sites in Fe doped NiS could dramatically lower the energy barrier for the rate determining elementary reaction, thus contributing to the active oxygen evolution.