Cobalt Substitution on SnS-rGO Composites for Efficient Oxygen and Hydrogen Evolution Reactions

To overcome the high cost of established electrocatalysts (viz., Pt/C and RuO2), there is a pressing need to replace them with highly efficient, cost-effective, and sustainable electrocatalysts. In this study, a series of Co-substituted orthorhombic tin sulfide-reduced graphene oxide (SnS-rGO) [CTSx-rGO, (x: 0.1 to 0.3)] catalysts were produced via a one-pot hydrothermal process. In potassium hydroxide (1.0 mol/L), CTSx-rGO acts as a highly competent and stable catalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) owing to the cumulative effect of Co and SnS-rGO composites. Co substitution improves the electrochemical active surface area (ECSA), reduces the Rct (charge-transfer resistance), and tunes the electronic configuration. The resulting CTS0.2-rGO composite exhibited exceptional performance toward the OER and HER activities by offering relatively small overpotentials of 323.0 and 233.1 mV at 20 mA/cm2, respectively, with long-term stability up to 50 h and high ECSA that is attributable to the improvement of the specific surface area and ample active sites resulting from the in situ structural and morphology change in SnS-rGO with Co substitution. This work facilitates and strengthens the development of an efficient Co-substituted SnS-rGO-based heterostructure electrocatalyst for overall water splitting.