Sulfur-modified nickel selenide as an efficient electrocatalyst for the oxygen evolution reaction

The sluggish four-electron transfer of the oxygen evolution reaction (OER) limits the performance of water electrolyzers.Hence,OER electrocatalysts based on earth-abundant elements are urgently needed.Heteroatom doping has been an efficient approach to boost the intrinsic OER activity of the active sites by modifying the electronic structure.Here,a simple anion substitution strategy is reported that increases the OER activity of nickel selenides via a one-step hydrothermal treatment of a metal–organic framework precursor.The resulting S-substituted NiSenanoparticles display distortion of their crystal lattice.As expected,the sulfur substitution modifies the electronic structure of NiSeand leads to outstanding electrocatalytic activity.All the S-substituted NiSecatalysts exhibit higher OER activities than the original NiSe.The optimized catalyst achieves a current density of 10 mA cmat an overpotential of 275 mV with a Tafel slope of 64 mV decin 1.0 M KOH.In addition to its electrochemical activity,the S-NiSe-2catalyst also exhibits good stability with only a 7.5%increase in overpotential at 50 mA cmafter 100hours.This work demonstrates one strategy to modify the electronic structure of transition metal compounds by anion regulation.