Evolution of photocatalytic activity of CeO2–Bi2O3 composite material for wastewater degradation under visible-light irradiation

Abstract

The Ce-doped bismuth oxide have been fascinated significantly due to the potential applications in ecological decontamination by photodegradation of the dye pollutants and agrochemical wastewater in to ecofriendly byproducts. Ceria (CO), Bismuth oxide (BO) and Ce-modified bismuth oxide (CBO) nanocrystalline materials were synthesized and thoroughly characterized by XPS, powder XRD, SEM-EDS, FT-IR, Raman, UV–Visible diffuse reflectance (UV–vis-DRS), photocurrent measurements, electrochemical impedence spectroscopy and photoluminescence (PL) spectral analysis. The band gap energy of Bi2O3 was reduced from 3.35 to 2.64 eV, the transformation of the monoclinic (α-Bi2O3) phase to the tetragonal (β-Bi2O3) phase and increase in BET surface area was observed upon Ce4+ doping into BO. Low fluorescence intensity, lesser arc radius of the Nyquist plots, high photocurrent response of CBO specifies a reduction in the rate of recombination of photogenerated electron and hole pair. The photocatalytic activity of BO, CO and CBO were examined for photodegradation of methylene blue (MB), cotton blue (CB) and agrochemical industrial wastewater (ACIWW) under visible light treatment. CBO exhibited greater degradation of MB, CB and ACIWW whereas pristine BO was less active in the degradation of pollutants. The greater photocatalytic activity of CBO is ascribed to stronger absorption of visible-light energy because of the higher surface area and shrinking of band gap energy as well as the easy production of •OH radicals during the photocatalytic reaction evidencing from scavenger studies. Even after five cycles of photodegradation of MB, CB and ACIWW, the photocatalyst CBO is found to be consistent in photocatalytic activity and powder XRD pattern as compared to pure CBO material.