Copper tungsten sulfide nanocubes decorated with rGO/MWCNT for overall water splitting

Abstract

Delivering clean hydrogen fuel from water electrolysis is effective approach for the present hydrogen economy. Typically, to construct cost-effective and highly proficient electrocatalysts is difficult, particularly bifunctional electrocatalysts for overall water splitting is immensely required. In this work, novel combination of Cu2WS4/rGO/MWCNT nanocomposites were synthesized and showed superior electrocatalytic activity towards overall water-splitting performance. From XRD analysis, we have confirmed the formation of a ternary composite of Cu2WS4/rGO/MWCNT, which belongs to the crystal structure of a tetragonal system with I-42 m (121) space group. The Raman spectra have also confirmed the successful preparation of ternary metal sulfide with its carbon composites. The morphology of nanostructure formation of Cu2WS4 nanocubes comprised of rGO sheets and MWCNT uniformly. Cu2WS4/rGO/MWCNT composite contained 23.5 wt.% of Cu, 34.2 wt.% of W, 19.0 wt.% of S, and 23.3 wt.% of C. In the half-cell experiment, the electrocatalyst of Cu2WS4/rGO/MWCNT exhibited 231 mV overpotential value for OER and 96 mV for HER and low 41 mV/dec Tafel slope value for OER and 81 mV/dec for HER. The combination of ternary metal sulfide with carbon contents can effectively improve the charge transfer (Rct = 1.89 Ω for OER and 0.52 Ω for HER), enhance the electrochemically active surface area (155 cm2 for OER and 91.7 cm2 for HER), and defend electrocatalyst in long-term stability. Owing to above advantages, electrocatalyst exhibits high activity in both OER and HER performances. Specifically, it requires low 1.55 V applied voltage to reach the 10 mA/cm2, which has potential material for overall-water splitting performances.