Electrochemical Oxygen\nEvolution Catalyzed by Zn_0.76Co_0.24S‑Enriched\nZnCo₂S₄/ZnCr₂O₄ Nanostructures

Abstract

Finding a suitable replacement for\nexpensive and scarce\nprecious\nmetal electrocatalysts for the oxygen evolution reaction (OER) remains\na challenging task. There is a need to research highly efficient and\nlong-lasting catalysts based on transition metals that are readily\navailable on Earth for electrochemical oxygen evolution. In this study,\nzinc cobalt sulfide (ZnCo₂S₄) was derived by\nhydrothermal treatment of metal salt precursors and thioacetamide,\nfollowed by calcination at 700 °C for ZnCr₂O4 to create\na ZnCo₂S₄/ZnCr₂O₄ composite\nnanostructure enriched with Zn_0.76Co_0.24S. The\nelectrochemical performance of the composition-dependent ZnCo₂S₄/ZnCr₂O₄ nanostructure\nenriched with Zn_0.76Co_0.24S was then tested\nalong with its constituents, and it was found that the OER activity\nis not linearly proportional to the composition. We also evaluated\nthe OER activity at pH 7.0 in a neutral medium and the OER electrochemical\nperformance in an alkaline medium. Zn–Co–S is preferable\nto Zn- and Cr-based thio-spinel as it increases electronic conductivity\nand decreases charge transfer resistance. Both of these properties\nare necessary for generating the high oxidative valency of Co species\nduring the OER process. The material’s unique composition and\nremarkable stability make it highly desirable for future research\nin this field.