Reduced graphene oxide–copper thiotungstate composite for enhanced photoelectrochemical performance

Abstract

Developing efficient photoanodes with higher charge separation and light harvesting ability remains a crucial challenge. For this purpose, we have used a reduced graphene oxide (rGO) electron-conducting scaffold to improve the charge transfer properties in the ternary transition metal chalcogenide Cu₂WS₄ (i.e., CWS). The photoluminescence (PL) studies reveal a weakened intensity of the PL band in CWS-rGO compared to CWS. In addition, fluorescence decay suggests an average lifetime of 1.6 ns and 1.16 ns for the CWS and CWS-rGO composite, respectively. The improved performance of the binary composite may be attributable to the remarkable electron transfer characteristics of the highly conductive rGO that facilitate the easy transport and more extended separation of charge carriers. Furthermore, the photoelectrochemical (PEC) measurements confirm the improved charge separation. The CWS-rGO composite exhibits a higher photocurrent density of 1.18 mA cm⁻², while the bare CWS was around 0.45 mA cm⁻² at 1.98 V vs. RHE. Furthermore, a higher applied bias photon-to-current efficiency (ABPE), a better transient photocurrent response, and a lower charge transfer resistance in the binary composite confirm the results obtained from the linear sweep voltammetry plots. This work demonstrates that incorporating rGO in CWS is an efficient approach towards accelerating the separation of charge carriers and achieving a better PEC performance of the CWS photoelectrode.