Tuning of reduced graphene oxide thin film as an efficient electron conductive interlayer in a proven heterojunction photoanode for solar-driven photoelectrochemical water splitting

Abstract

Although bismuth vanadate (BiVO4) has shown excellent photoelectrochemical (PEC) properties and is a good candidate of photoanode materials, the solar-driven PEC water splitting performance is still remained below its full potential due to the fast recombination and sluggish charge mobility of photogenerated charge carriers. Previously, we have communicated a proven Type II staggered vanadium pentoxide (V2O5)/BiVO4 heterojunction photoanode that could improve the photocurrent density. This study aimed to examine the effect of introducing an rGO thin film as an efficient electron conductive interlayer in a proven V2O5/BiVO4 heterojunction photoanode, and subsequently tuning the rGO film thickness in achieving the optimum PEC performance. The resultant ternary photoanode structure of V2O5/rGO/BiVO4 was characterised by using field emission-scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), UV-vis spectroscopy, X-ray diffractometer (XRD), Raman spectroscopy and photoluminescence (PL) measurements. Results showed that the interlayer rGO thin film arising from the sequential drop cast and electrochemical reduction of 320 μL ultrasonicated GO solution resulted in the optimal photocurrent density of 2.1 mA/cm 2 at 1.5 V vs. Ag/AgCl. Furthermore, the chemical physics surrounding the photogenerated charge carrier transfer for heterojunction V2O5/BiVO4 was validated for the structure with and without the rGO interlayer. In particular, the electrochemical impedance spectroscopy (EIS) was used to measure multiple resistances at the FTO/semiconductor, semiconductor/semiconductor and semiconductor/electrolyte interfaces. Additionally, the charge transfer (Kt) and recombination (Kr) rate constants for the heterojunction V2O5/BiVO4 with the rGO interlayer were quantified using intensity modulated photocurrent spectroscopy (IMPS). Finally, the PEC H2 evolution rate from the ternary V2O5/rGO/BiVO4 photoanode was measured to be 32.7 μmol/hr, which was about 3-fold higher than the bare V2O5/BiVO4 heterojunction photoanode.

Bismuth-Graphene Nanohybrids: Synthesis, Reaction Mechanisms, and Photocatalytic Applications—A Review

“…This important work provides a new entry to the use of g-C3N4 in the design of new and efficient water division systems [224]. Chong et al [230] reported V2O5/rGO/BiVO4 heterojunction (Figure 8) as an efficient photo-electrochemical water division photoanode. .…”

“…The majority of previous studies on the conversion of NOx gases have involved different lasers [254], spectroscopic (such as infrared (IR), [255], and chemiluminescence (CL) [256] or electrochemical techniques [257] for the detection of NOx reaction products. The use of high-resolution MS for biomedical applications to detect NO [230] and indirectly semiconducting metal oxides [231] has been described. The main cause of water pollution is industrial wastewater discharge.…”