Development of spray pyrolysis-synthesised Bi₂O₃ thin films for photocatalytic applications

Photocatalysis is a green and cost-effective approach to environmental remediation. While TiO₂ is considered one of the benchmark photocatalysts, alternative materials such as Bi₂O₃ have recently attracted increasing scientific attention as prospective visible light photocatalysts. This study aimed to develop a strategy for Bi₂O₃ thin film deposition via ultrasonic spray pyrolysis and systematically study process variables for the deposition of β-Bi₂O₃ thin films for photocatalytic applications. To achieve the aim, the precursor solution concentration as well as deposition and annealing temperature were optimised. The structural, optical, morphological, chemical and wettability properties of the obtained Bi₂O₃ thin films were investigated with respect to the effect on the photocatalytic oxidation of 10 ppm methyl orange (MO). The highest photocatalytic activity (48% in 5 h) under UV-A was recorded for the β-Bi₂O₃ film deposited using 0.1 M precursor solution at 300 °C and heat-treated for 1 h in air at 350 °C. Deposition at 300 °C resulted in an amorphous film structure, whereas annealing at 350 °C led to the formation of the β-Bi₂O₃ phase with the dominant facet orientation (220). These results show the suitability of spray pyrolysis for the deposition of Bi₂O₃ thin films with promising results for MO dye degradation, expanding the range of suitable photocatalytic materials.