Boosted visible light dye-decontamination and colossal dielectric constant features of Bi2O3: Role of In, Cu and Li-dopants

Abstract

This study focused on improving the optical, dielectric properties, and photocatalytic efficiency of Bi2O3, a prominent photocatalyst with challenges like limited visible light absorption and rapid electron-hole pair recombination. Using an adapted sol-gel technique, pure Bi2O3, In, Cu and Li-doped Bi2O3 visible-light-driven photocatalyst were synthesized. X-ray diffraction (XRD) confirmed monoclinic Bi2O3 formation. The inclusion of In, Cu, and Li ions into the Bi2O3 lattice was evidenced by alterations in diffraction peak intensities, lattice parameters, and changes in average crystallite size. Vibrational spectra corroborated the formation of pure α-Bi2O3 with slight shifts in transmittance bands, aligning with the XRD findings. Morphological investigation via scanning electron microscopy (FE-SEM-EDX) confirmed the purity of the synthesized nanocompositions and unveiled that the doping induces distinct morphological changes in Bi2O3 nanoparticles, resulting in increased porosity and formation of round and needle-like shapes (In-doped), coalescence of particles (Cu-doped), and fused agglomerates with altered particle size distribution (Li-doped). Optical analysis demonstrated a red shift in the band gap energy of α-Bi2O3 (initially 2.90 eV), with In, Cu, and Li doping, resulting in band gaps of 2.77 eV, 2.78 eV, and 2.88 eV, respectively, accompanied by high refractive indices exceeding 2.0, rendering them suitable for optical applications. Both Cu and Li doping led to enhanced relative permittivity (εʹ) values, with the Li-doped sample displaying remarkable εʹ values at low frequencies (up to 1000 Hz). The In, Cu and Li doping has the effect of reducing PL (photoluminescence) emission intensity while simultaneously diminishing radiative recombination and promoting the separation of photogenerated charge carriers. The doped samples demonstrated superior degradation performance, with In-doped and Cu-doped samples achieving degradation efficiencies of 99% and 91%, respectively, within 180 min. This remarkable performance can be attributed to their visible-light-responsive band gaps, increased electron-hole trapping sites, and distinct morphological features.