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Description
An in-depth investigation was carried out to determine the relationship between morphological, structural conversion, and photoelectrochemical water-splitting properties of β-$Bi_2O_3$ nanostructured thin film annealed at temperatures ranging from $500^oC$ to $650^oC$. Apart from the phase transformation it has also been observed that the basic nanostructure were converted from nanoflakes to nanoworms via nanorods. These transformation results in the red shifting in the optical band gap. Transformation occurs in the basic $Bi_2O_3$ leads to the emergence of new non–stoichiometric $Bi_2O_{2.33}$ have been visualized due to the fast annealing at $600^oC$ which enhance the oxygen vacancies as analyzed by the XPS. Consequence of the annealing up to $600^oC$ enhanced the photocurrent density up to (~ 1.53 $mAcm^{-2}$ at 1.23 V vs RHE) which shows 1.7 times higher than basic β-$Bi_2O_3$ (̴ 0.90 $mAcm^{-2}$ at 1.23 V vs RHE) in the $Na_2SO_3$ electrolyte. However in the neutral $Na_2SO_4$ electrolyte the photocurrent density of $Bi_2O_3$ at $600^oC$ was found (~ 0.21 $mAcm^{-2}$ , 1.23 V vs RHE) which shows 2.6 times higher than basic β-$Bi_2O_3$ (~ 0.08 mAcm -2 , 1.23 V vs RHE). Above this shifting in the onset potential for all the samples were found on altering the electrolyte from $Na_2SO_4$ (pH=7) to $Na_2SO_4$ (pH=9). The Mott-Schottky and EIS were demonstrated for scrutinizing the charge kinetics for all the photoelectrodes. These findings contribute a favorable impact of annealing over the structure and the morphology of the material which can produce high photoelectrochemical ability.
