Cobalt Substitution\non SnS-rGO Composites for Efficient\nOxygen and Hydrogen Evolution Reactions

To overcome the high cost of established electrocatalysts\n(viz.,\nPt/C and RuO<sub>2</sub>), there is a pressing need to replace them\nwith highly efficient, cost-effective, and sustainable electrocatalysts.\nIn this study, a series of Co-substituted orthorhombic tin sulfide-reduced\ngraphene oxide (SnS-rGO) [CTS<i>x</i>-rGO, (<i>x</i>: 0.1 to 0.3)] catalysts were produced via a one-pot hydrothermal\nprocess. In potassium hydroxide (1.0 mol/L), CTS<i>x</i>-rGO acts as a highly competent and stable catalyst for both oxygen\nevolution reaction (OER) and hydrogen evolution reaction (HER) owing\nto the cumulative effect of Co and SnS-rGO composites. Co substitution\nimproves the electrochemical active surface area (ECSA), reduces the <i>R</i><sub>ct</sub> (charge-transfer resistance), and tunes the\nelectronic configuration. The resulting CTS0.2-rGO composite exhibited\nexceptional performance toward the OER and HER activities by offering\nrelatively small overpotentials of 323.0 and 233.1 mV at 20 mA/cm<sup>2</sup>, respectively, with long-term stability up to 50 h and high\nECSA that is attributable to the improvement of the specific surface\narea and ample active sites resulting from the in situ structural\nand morphology change in SnS-rGO with Co substitution. This work facilitates\nand strengthens the development of an efficient Co-substituted SnS-rGO-based\nheterostructure electrocatalyst for overall water splitting.