Self-ZIF template-directed synthesis of a CoS nanoflake array as a Janus electrocatalyst for overall water splitting

Abstract

It is crucial to develop non-noble metal bifunctional electrocatalysts with high activity and favorable stability for overall water splitting under basic conditions for renewable-energy conversion techniques. Direct assembly of active materials on carbon cloth is a promising approach to realize flexible electrodes for electrocatalysis. Herein, a facile strategy is proposed to synthesize a cobalt sulfide nanoflake array on carbon cloth (CoS NF/CC) as an efficient electrocatalyst for overall water splitting through hydrothermal sulfidation from a ZIL-L–Co derived Co₃O₄ precursor. The obtained CoS NF/CC has increased catalytic active sites and improved charge-transfer kinetics enabled by the sulfidation process, as well as facilitated electrolyte penetration and gas diffusion enabled by the open-shelled nanoarray structure. This electrode exhibits remarkable bifunctional electrocatalytic activity toward water splitting with a low overpotential of 247 mV to achieve a current density of 50 mA cm⁻² for the HER and 310 mV to achieve 10 mA cm⁻² for the OER. Furthermore, a current density of 10 mA cm⁻² was achieved at a cell voltage of 1.72 V using a full alkaline electrolyzer with the CoS NF/CC as both the cathode and anode, and this performance value could be well maintained for ∼15 h.