Waxberry-Like MnS/Ni₃ S₄ as High-Efficiency Bi-Functional Catalyst for Zn-Air Batteries

In this paper, a waxberry-like MnS/Ni₃ S₄ composite catalyst was designed and synthesized. In this coating structure, MnS is located inside and Ni₃ S₄ is wrapped on the surface to form a spherical structure. This structure makes the material show excellent stability in the electrocatalytic process. The diffusion staggered region structure formed at the two-phase interface greatly enhances the synergistic interaction between MnS and Ni₃ S₄ . At the same time, the defects and vacancies formed by the diffusion mechanism at the interface of the two phases increase the active site and improve the interfacial electron transfer kinetics. Therefore, MnS/Ni₃ S₄ composites showed good catalytic performance for ORR/OER. At 10 mA cm^-2 , the overpotential of it is only 320 mV, and the half-wave potential can reach 0.81 V. The catalyst also exhibited extraordinary cycle stability and small voltage gap when used as cathode of Zn-air batteries. When the current density is 3 mA cm^-2 , the cyclic discharge can be stable for 400 h and the voltage difference between the front and back does not increase more than. When the current density increases to 5 mA cm^-2 , the cyclic charge and discharge can be stable for more than 300 h.