Reduced band gap & charge recombination rate in Se doped alpha-Bi2O3 leads to enhanced photoelectrochemical and photocatalytic performance: Theoretical & experimental insight

For better utilization of solar spectrum and complete redox of water for water splitting applications, it is required to have a semiconductor which is photoactive in visible region. In this study, we report theoretical and experimental investigations on morphological and opto-electronic modifications induced in alpha-Bi2O3 due to Selenium (Se) doping tested for photoelectrochemical (PEC) & photocatalytic properties. Density Functional Theory (DFT) calculations revealed band gap reduction and direct to indirect transitions in Se-doped alpha-Bi2O3, This reduction in band gap is attributed to hybridization of Se p & Bi s in valence band and Se d & Bi p orbital in conduction band. To support this finding experimentally, we synthesized Se-doped alpha-Bi2O3 using simple chemical precipitation method and measured its band gap using photoluminescence and UV Vis spectroscopy. Experimental results also confirmed the reduction in band gap energy and recombination rate of charge carriers as compared to pristine alpha-Bi2O3 sample. PEC study of Se-doped alpha-Bi2O3 showed an increased photocurrent density, charge carrier density and lowered impedance, which indicates its efficient solar spectrum utilization and better hydrogen generation efficiency. Photo catalytic measurement also revealed higher rate of dye degradation with Se dopd alpha-Bi2O3