Hierarchical Porous Ni3S4 with Enriched High-Valence Ni Sites as a Robust Electrocatalyst for Efficient Oxygen Evolution Reaction

Electrochemical water splitting is a common way to produce hydrogen gas, but the sluggish kinetics of the oxygen evolution reaction (OER) significantly limits the overall energy conversion efficiency of water splitting. In this work, a highly active and stable, meso-macro hierarchical porous Ni S architecture, enriched in Ni is designed as an advanced electrocatalyst for OER. The obtained Ni S architectures exhibit a relatively low overpotential of 257 mV at 10 mA cm and 300 mV at 50 mA cm . Additionally, this Ni S catalyst has excellent long-term stability (no degradation after 300 h at 50 mA cm ). The outstanding OER performance is due to the high concentration of Ni and the meso-macro hierarchical porous structure. The presence of Ni enhances the chemisorption of OH , which facilitates electron transfer to the surface during OER. The hierarchical porosity increases the number of exposed active sites, and facilitates mass transport. A water-splitting electrolyzer using the prepared Ni S as the anode catalyst and Pt/C as the cathode catalyst achieves a low cell voltage of 1.51 V at 10 mA cm . Therefore, this work provides a new strategy for the rational design of highly active OER electrocatalysts with high valence Ni and hierarchical porous architectures.