Facile engineering of CoS/rGO heterostructures on carbon cloth for efficient all-pH hydrogen evolution reaction and alkaline water electrolysis

Developing a cost-effective and commercially viable catalyst from non-noble metals that exhibits superior performance in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) presents a significant challenge due to the distinct electrocatalytic mechanisms involved in each process. Herein, we engineered a three-dimensional, self-supporting heterostructure on carbon cloth (CC) using facile two-step electrodeposition, consisting of reduced graphene oxide (rGO) and cobalt sulfide (CoS), aimed at enhancing the efficiency of overall water electrolysis. The porous rGO network promoted the anchoring and vertical growth of CoS nanosheets, while the heterojunction between rGO and CoS enhanced the catalyst's stability remarkably. The CoS/rGO@CC catalyst exhibited extremely low overpotentials for both HER (η10=76.3 mV) and OER (η10=290.4 mV), maintaining these stable overpotentials for more than 24 hours, matching the performance of leading electrocatalysts based on noble metals. Moreover, by utilizing CoS/rGO@CC as both cathode and anode, we achieved overall water splitting with just 744 mV @10 mA cm-2. Theoretical calculations validated the synergistic effect of rGO and CoS nanosheets on enhancing HER and OER processes. Additionally, experimental data highlighted the CoS/rGO@CC catalyst's exceptional HER catalytic ability across varied pH levels, which provides a promising strategy to design low-cost and high-performance electrocatalysts for other energy-related applications.