Cu 2 S Nanoflakes Decorated with NiS Nanoneedles for Enhanced Oxygen Evolution Activity.

Metal sulfides are considered excellent materials for oxygen evolution reaction because of their excellent conductivity and high electrocatalytic activity. In this report, the NiS-Cu 2 S composites were prepared on copper foam (NiS-Cu 2 S-CF) using a facile synthetic strategy. The scanning electron microscopy results confirmed that the NiS nanoneedles were successfully grown on Cu 2 S nanoflakes, greatly increasing the active sites. Particularly, the optimized 15% NiS-Cu 2 S-CF composite demonstrated excellent oxygen evolution activity with a small overpotential of 308 mV@20 mA cm -2 , which is significantly smaller than that of noble metal-based electrocatalysts and other NiS-Cu 2 S-CF composites. The enhanced oxygen evolution activity is attributed to the unique morphology that can provide ample active sites, rich ion-transfer pathways, and the synergistic effect between NiS and Cu 2 S, which can boost the electron transfer rate.