Photocatalytic Performance of Ta₂O₅/BiVO₄ Heterojunction for Hydrogen Production and Methylene Blue Photodegradation

Forming semiconductor heterojunction is promising for improved photocatalytic performance due to synergistic combination of the best properties of each material. The present study reports a simple hydrothermal strategy to form n-n heterojunction of Ta₂O₅ nanotubes and BiVO₄ microstructures. The Ta₂O₅/BiVO₄ heterojunctions were characterized by Raman spectroscopy, UV Vis diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and their photocatalytic activity was evaluated by hydrogen production and photodegradation of methylene blue (MB) dye in aqueous medium under AM 1.5 G (100 mW cm²) condition. The heterojunctions have optical absorption in the visible region (200 500 nm) with crystal structures defined as monoclinic for BiVO₄ and orthogonal for Ta₂O₅. For MB photodegradation, the Ta₂O₅/BiVO₄ obtained via hydrothermal route showed a photodegradation of 72.3%, compared to 28.3% presented by the sample produced through the mechanical mixture, with the maintenance of 86.4% of its photocatalytic performance after 3 cycles of photodegradation. For H₂ production, hydrothermally prepared Ta₂O₅/BiVO₄ generated 10.2 μmol g^-1 of H₂ in 3 h; while Ta₂O₅ nanotubes and mechanical Ta₂O₅/BiVO₄ mixture shows 6.82 and 2.80 μmol g^-1, respectively. The results suggest that Ta₂O₅/BiVO₄ is a promising material for applications in photocatalysis, promoting sustainable energy production through hydrogen and for the treatment of effluents containing cationic dyes.

Keywords:
photocatalysis; hydrogen; n-n heterojunction; tantalum dioxide; photodegradation