Superior Oxygen Electrocatalysis on Nickel Indium Thiospinels for Rechargeable Zn–Air Batteries

Abstract

Developing active bifunctional oxygen catalysts to eliminate/reduce the reliance on precious-metal-based ones in metal–air batteries is nowadays of great importance. Here, we report the synthesis of nickel indium thiospinel nanosheets supported on carbon nanofibers (denoted as NiIn2S4/CNFs) via a facile in situ solvothermal growth process and, for the first time, demonstrate its superior bifunctional oxygen electrocatalytic performances as a precatalyst. Electrocatalytic experiments show that NiIn2S4/CNFs not only exhibits a positive half-wave potential of 0.81 V for the oxygen reduction reaction (ORR) but also delivers a lower overpotential of 0.39 V for the oxygen evolution reaction (OER) at 10 mA cm–2, outperforming those of monometallic Ni or In sulfides. Theoretical calculations confirm that the (220) and (111) plane in NiIn2S4 are selectively active to the ORR and OER, respectively. Apart from the intrinsic nature of NiIn2S4, the superior OER activity of NiIn2S4/CNFs is also related to the oxide/hydroxide species in-situ-formed on NiIn2S4 surface under the OER condition. Moreover, the developed NiIn2S4/CNFs pre-catalyst is demonstrated to be an efficient air-cathode for Zn–air batteries. This work brings a new perspective for designing various ternary thiospinels for energy conversion and storage.