Optimization of growth condition of n-type Bi2O3 semiconductors for improved photoelectrochemical applications

For the purpose of hydrogen production with free solar energy, the photoelectrochemical (PEC) water-splitting process grabbed attention as a sustainable route. PEC systems offer several benefits to produce hydrogen, including low environmental impact. For the PEC water oxidation process, Bi₂O₃ (BO) is considered a very promising semiconductor due to its moderate bandgap of 2.65 eV and can exist in various phases. In order to determine the optimum growth temperature of Bi₂O₃ for the PEC water splitting reaction and the photocatalytic dye degradation reaction, a series of bismuth (III) oxide semiconductors (SC) is developed in the present work using bismuth nitrate as a precursor varying the annealing temperatures (200–800 °C) in air. The optimized Bi₂O₃ exhibits the highest photo-activity for the degradation of Rhodamine B target pollutants, which was confirmed by different physicochemical and photocatalytic experimental studies. The sample annealed at an optimized temperature of 650 °C achieved the maximum photocurrent of 0.19 mA cm⁻² for water splitting reaction in the presence of phosphate buffer solution with 0.1 M Na₂SO₄ (pH 7), under periodic chopped illumination of UV–vis light with 100 mW cm⁻² light intensity at 1.17 V versus Ag/AgCl. The n-type nature of the semiconductor has been determined through Mott-Schottky analysis. Bi₂O₃ facilitates the photo-activated electron–hole charge separation and migration due to its relative band position, and as a result, the stable performance of the semiconductor was also reported. The degradation reaction in the presence of scavenger materials such as triethanolamine (TEOA), tertiary butyl alcohol (TBA) and p-benzoquinone (BQ) has also been studied to propose the most plausible mechanism of degradation reaction.