The role of SO42− in manipulating partial charge distribution to boost alkaline water oxidation in Co9S8/C–Ni(OH)2

Transition metal sulfides (TM sulfides) has long been regarded as highly promising materials for catalyzing oxygen evolution reaction (OER). The function of TM sulfides in OER occurs on TM oxyhydroxide and SO 4 2− , which are formed through surface reconstruction under certain potentials. It is worth noting that the impact of SO 4 2− on the local charge distribution among atoms, a crucial determinant of OER performance, has been insufficiently studied. This study aims to investigate the role of SO 4 2− in mediating the partial redistribution of charges among Co, Ni and O atoms on a precatalyst Co 9 S 8 /C–Ni(OH) 2 electrode. The electrode undergoes self-reconstruction to form a CoOOH/SO 4 2− /NiOOH structure on its surface that is active for the OER. The results demonstrate that SO 4 2− facilitates the local charge redistribution of active atoms, leading to optimized adsorption energy of OER intermediates and increased redox center of the material. Furthermore, SO 4 2− serves as an electron mediator in the OER process under varying applied voltages. Consequently, CoOOH/SO 4 2− /NiOOH achieves a Tafel slope of 56 mV dec −1 , an overpotential of 250 mV, and maintains a high stability for over 100 h at a current density of 20 mA cm −2 . Overall, this research provides valuable insights into catalytic reaction mechanisms and the design of efficient composite catalysts.