Enhanced visible‑light degradation of cationic dyes over BiTaO4/BiVO4 heterostructure nanoplates

Bismuth heterojunction nanocomposites of BiTaO 4 nanoplates and BiVO 4 nanostructures were successfully prepared to enhance the photocatalytic performance of two cationic dyes: methylene blue (MB) and rhodamine B (RhB). The heterostructured nanocomposite of BiTaO 4 /BiVO 4 demonstrates a specific surface area of 15.32 m 2 /g, achieving a two-fold increase over the 6.4 m 2 /g surface area of pure BiTaO 4 nanoplates. Mott-Schottky and UV–Vis measurements reveal the narrowing of the optical band gap of the newly fabricated heterostructure nanocomposites to 2.5 eV, enabling efficient charge generation and separation capabilities. The heterostructure nanocomposite of BiTaO 4 /BiVO 4 exhibits an enhanced degradation time constant of 0.098 min −1 for MB, which is 97 % faster than that of pure BiTaO 4 nanoplates at 0.002 min −1 . For RhB dye, a 57 % enhancement in the photodegradation time constants was recorded for BiTaO 4 /BiVO 4 with 0.045 min −1 compared to 0.019 min −1 for the pure BiTaO 4 nanoplates. The improved photocatalytic performance is attributed to efficient visible light absorption and effective charge generation and separation at the heterojunction active sites formed on the surface of BiTaO 4 nanoplates, as revealed by temporal response measurements. The transient photoresponse of BiTaO 4 /BiVO 4 nanocomposite shows faster time constants, with rise and decay times of τ R = 0.42 s and τ D 1 = 0.41 s, τ D 2 = 49.5 s, respectively. In comparison, the pure BiTaO 4 nanoplates exhibit rise times of τ R 1 = 0.46 s and τ R 2 = 6.36 s, while their decay times are τ D 1 = 0.72 s and τ D 2 = 15.73 s, where τ R and τ D are the rise and decay time constants, respectively. The heterostructure nanocomposites exhibit a higher photocurrent density of 0.65 µA/cm 2 , compared to 0.35 µA/cm 2 for pure BiTaO 4 . This study provides valuable insights into photocatalysis reaction enabled by a novel heterojunction formation between BiTaO 4 and BiVO 4 .