Self-supported fabrication and electrochemical water splitting study of transition-metal sulphide nanostructured electrodes

Abstract

Design of efficient, low-cost and durable water splitting electrocatalyst is a central to the field of electrochemical energy conversion and storage technologies. Herein, we report a facile fabrication of a variety of nanostructured transition metal sulphides (iron sulphides (FeS), cobalt sulphides (CoS), nickel sulphides (NiS), and copper sulphides (CuS)) on a bare nickel foam (NiF) substrate via a one-step electrochemical strategy. The fabricated FeS, CoS, NiS and CuS nanostructures were effectively employed as potential electrodes for enhanced oxygen evolution reaction (OER) in presence of an alkaline electrolyte (1.0 M KOH). Our primary electrocatalytic OER study reveals that the FeS nanostructures exhibited the best activity in terms of low onset potential (∼1.51 V vs. RHE), small over-potential (η) (∼0.32 V@10 mA cm⁻²), and Tafel slope (∼0.069 V dec⁻¹), and high durability in comparison to the CoS, NiS and CuS nanostructures. A unique three-dimensional sheet-like morphology, high electrochemical active surface area (ECASA), low electrochemical impedance characteristics, rapid electron-transfer kinetics, and high structural solidity enable this novel FeS nanomaterial to be a distinct and promising electrode material for the OER activity. Thus, the complete electrocatalytic OER activity of the transition metal sulphide nanostructures follows the order: FeS > CoS > NiS > CuS. Our results on the optimized design of transition metal sulphide-derived electrodes based on the chemical composition, surface morphology, abundant active sites, etc., would further improve the OER activity for water electrolysis.