Highly Efficient and Durable Electrocatalyst Based on Nanowires of Cobalt Sulfide for Overall Water Splitting

Abstract Water electrolysis to generate hydrogen and oxygen at low overpotential is one of the main requirements for clean and renewable energy technology. Currently, precious‐metal‐based catalysts such as Pt, IrO_2, and RuO₂ are being used for water electrolysis limiting its wide range of applicability due to their high cost and rare‐earth abundance. In this research, we have used nanowires of cobalt sulfide as an efficient electrocatalyst for overall water splitting. Directly grown nanowires of cobalt sulfide on nickel foam provided superior electrocatalytic activities favoring electron transfer. High surface area and porosity of the nanowires allowed easy escape of the generated oxygen and hydrogen. Cobalt sulfide nanowires required an overpotential of 299 and 217 mV to achieve a current density of 10 mA/cm² for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Furthermore, nanowires of cobalt sulfide required a low cell voltage of 1.66 V to achieve a current density of 10 mA/cm² which is among the best‐reported value. A facile preparation method, outstanding bi‐functionality, and electrochemical stability of cobalt sulfide as both HER and OER electrocatalyst, suggest that cobalt sulfide could be a promising material for commercial applications in water electrolysis.