Tailoring photocatalytic performance of spin-Coated BiVO

Water pollution from synthetic dyes, particularly the toxic and non-biodegradable Rhodamine B (RhB), has spurred the development of efficient semiconductor-based photocatalytic technologies. Bismuth vanadate (BiVO₄), with a band gap of ~2.3–2.4 eV, is a promising visible-light-responsive photocatalyst. In this work, BiVO₄ thin films were fabricated on FTO substrates via spin coating, followed by calcination at 500 °C for varying durations (5, 10, 15, 20, and 25 min). The structural, morphological, and optical properties were characterized using XRD, SEM-EDX, UV-Vis DRS, and photoluminescence (PL) spectroscopy. Characterization confirmed the formation of monoclinic BiVO₄ with high crystallinity, a uniform surface morphology, and an optimal distribution of Bi and V elements. The optical band gap decreased from 2.30 eV (5 min) to 2.23 eV (15 min), enhancing visible-light absorption. PL spectra indicated reduced emission intensity for the 15 min sample, suggesting improved charge-separation efficiency. Photocatalytic experiments demonstrated that the 15 min calcined BiVO₄ achieved the highest photocurrent density (90 µA/cm2) and an RhB degradation efficiency of 85.96% within 100 min, following pseudo-first-order kinetics. These results highlight that spin-coated BiVO₄ thin films with optimised calcination time exhibit superior structural, optical, and photoelectrochemical properties, making them promising candidates for visible-light-driven wastewater remediation.