Hollow tubular Co3S4/NiS/FeS as high-efficiency tri-functional electrocatalyst for Zn-air battery and overall water splitting

In this paper, a hollow tubular Co 3 S 4 /NiS/FeS heterogeneous composite was prepared by an ordinary hydrothermal procedure. The inner Co 3 S 4 can act as the carrier of the outer NiS/FeS, and the outer NiS/FeS can effectively prevent the collapse of the inner Co 3 S 4 hollow structure, ensuring the durability of the structure and performance in the cyclic charge-discharge test. The strong electronic interaction between Co 3 S 4 and NiS/FeS significantly improves the catalytic activity. It shows a small 230 mV overpotential at 10 mA cm −2 , which is superior to commercial RuO 2 . The Zn-air battery assembled with Co 3 S 4 /NiS/FeS catalyst showed outstanding stability over 2700 cycles with a narrow voltage gap of 0.67 V at 3 mA cm −2 . Flexible battery also combined based on this catalyst can generally be discharged/charged at each bending angle and the gap remained almost continuous. Furthermore, Co 3 S 4 /NiS/FeS also displays hydrogen evolution reactions activity, displaying a lower overpotential of 233 mV at 10 mA cm −2 . In the overall water splitting, Co 3 S 4 /NiS/FeS is used as both anode and cathode electrocatalyst , which can reach 10 mA cm −2 at 1.52 V, and the performance remains steady for 50 h. In conclusion, Co 3 S 4 /NiS/FeS is a potential tri-functional catalyst for ZABs and overall water splitting.