Tackling two different energy issues with one unique WS2-WO3/rGO nanocomposite: Energy storage and electrochemical hydrogen generation

Abstract

Ternary nanocomposite of WS₂-WO₃/rGO was synthesized by a facile one-step hydrothermal method aiming at exploring its multifunctionality both for storing as an electrochemical capacitor and generating energy as a electrocatalyst in hydrogen evolution reaction (HER). Thus, WS₂-WO₃/rGO was morphologically and structurally characterized and results suggested that WS₂ and WO₃ grow over rGO sheets, which guarantees an intimate contact between components. Evaluation of electrochemical performance stated how promising it can be for playing the roles of supercapacitor electrode and HER catalyst. The electrodes were prepared following the same methodology, regardless of the desired application. Specific capacitances of 1451 F g⁻¹ at 1 mV s⁻¹ and 728 F g⁻¹ at 1.25 A g⁻¹ were obtained, which are almost 2-fold higher than the values delivered by isolated components rGO and WS₂-WO₃. Besides that, the material achieved a capacitance retention of 91 % under 3000 voltametric cycles. Regarding WS₂-WO₃/rGO as HER catalyst, it displayed lower overpotential and lower Tafel slope (37.8 mV dec⁻¹) than the well-known platinum (58.58 mV dec⁻¹) in alkaline medium. Electrochemical Impedance Spectroscopy (EIS) analysis indicated that the ternary hybrid presents a lower charge-transfer resistance, corroborating its prominent performance in both applications. In this sense, this work addresses the feasibility of fully explore unique materials into a single design targeting at different functionalities.