CuS Nanosheets Decorated with CoS2 Nanoparticles as an Efficient Electrocatalyst for Enhanced Hydrogen Evolution at All pH Values

The design and fabrication of eco-friendly, highly efficient, and non-noble-metal-based catalysts are demanding challenges in energy-conversion technologies. Herein, we successfully synthesized CuS nanosheets decorated with CoS 2 nanoparticles through a facile route. The optimized 3% CoS 2 -7% CuS catalysts exhibited remarkable electrocatalytic performance, with excellent cyclic stability at all pH values for the hydrogen evolution reaction (HER). They exhibited lower Tafel slopes (46, 52, and 59 mV dec –1 ) and smaller overpotentials (62, 85, and 106 mV) at 10 mA cm –2 in 0.5 M H 2 SO 4, 1 M KOH, and 0.5 phosphate buffer aqueous solutions, respectively, than other CoS 2 /CuS, pure CoS 2, and pure CuS catalysts. We attribute their high electrocatalytic performance to their unique heterostructure and the synergistic effects between the constituent metal sulfides that provides a large interfacial contact area, numerous charge-transfer pathways, as well as abundant surface reaction active sites, enhancing the charge-carrier transfer during the HER activity.