Effect of annealing of β-Bi2O3 over enhanced photoelectrochemical performance

In-depth investigation was carried out to determine the relationship between morphological, structural conversion, and photoelectrochemical (PEC) performance of β-Bi2O3 nanostructured thin film annealed at temperatures ranging from 500 °C to 650 °C. Apart from the phase transformation it has also been observed that the basic nanostructure were converted from nanoflakes to nanoworms via nanorods. Transformation that occurs in the basic β-Bi2O3 leads to the emergence of new non–stoichiometric Bi2O2.33 due to the fast annealing at 600 °C which enhance the oxygen vacancies in the β-Bi2O3/Bi2O2.33 heterojunction as analyzed by the XRD and XPS. The annealing within the range (500oC–650 °C) results in the red shifting in the optical band gap. Consequence of the annealing up to 600 °C enhanced the photocurrent density up to (̴ 1.53 mAcm−2 at 1.2 V vs RHE) which shows 1.7 times higher than basic β-Bi2O3 (̴ 0.90 mAcm−2 at 1.2 V vs RHE) in the Na2SO3 electrolyte. However in the neutral Na2SO4 electrolyte the photocurrent density of β-Bi2O3 at 600 °C was found (̴ 0.21 mAcm−2, 1.23 V vs RHE) which shows 2.6 times higher than basic β-Bi2O3 (̴ 0.08 mAcm−2, 1.23 V vs RHE). Beyond this shifting in the onset potential for all the samples were found on altering electrolyte from Na2SO4 (pH = 7) to Na2SO3 (pH = 9). The Mott-Schottky and EIS were demonstrated for scrutinizing the charge kinetics for all the photoelectrodes. These results contribute a favorable impact of annealing over the structure and the morphology of the material which can produce high PEC ability.