Optimizing Precursor pH for Enhanced WO₃/BiVO₄ Heterojunction Photoanode Performance

Abstract

The pH of the precursor solution significantly influences the efficacy of WO₃/BiVO₄ heterojunction photoanodes; however, the exact impact on the photoelectrocatalytic (PEC) process remains unclear. This study objectively examines the influence of the pH of the WO₃ precursor on the structural, optical, and electrochemical characteristics of FTO/WO₃/BiVO₄ electrodes to enhance their performance in photoelectrochemical (PEC) applications. WO₃ and BiVO₄ are prepared via dip-coating, subsequently subjected to calcination at 500°C. The photoanode characteristic properties were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy, and electrochemical impedance spectroscopy (EIS). The results indicated that the electrode efficiently segregated charge carriers due to its reduced bandgap energy (2.15 eV) and substantial light absorption (λ = 576 nm) at pH 11. In comparison to Ag/AgCl, we obtained a significant increase in current density (1.91 mA/cm²) with the utilization of visible light at 1.0 V. This addressed to a significant capacitance (CPE = 1.19 × 10⁻⁵ F) and a small charge transfer resistance (Rct = 116 Ω). A uniform, detailed morphology was noted in the SEM images at a pH of 11, which enhanced interfacial bonding and charge transfer. The results emphasize the necessity of adjusting the precursor's pH to improve the efficacy of WO₃/BiVO₄ heterojunctions employed in solar-driven oxidation processes. These findings will facilitate the advancement of sophisticated photoelectrocatalytic applications for sustainable energy conversion.