One-pot hydrothermal preparation and defect-enhanced photocatalytic activity of Bi-doped CdWO4 nanostructures

In the field of photocatalysis, the suppression of electron–hole recombination through various defects has been an emerging trend to enhance photocatalytic activity. The separation efficiency of electron–hole recombination of well-explored wolframite structured monoclinic CdWO4, prepared using the one-pot hydrothermal method, was further improved by Bi3+ doping in CdWO4. Studies using the partial density of states illustrated that Bi 6s and 6p orbitals altered the electronic band structure to the extent of lowering the band gap, resulting in more photon absorption. The positron annihilation lifetime studies unveiled the formation of cluster defects such as oxygen (Vo0, Vo1+, Vo2+) along with cadmium vacancies ([Formula Omitted]) in Bi-doped CdWO4. The coexistence and synergy of more adsorption sites of Vo0, Vo1+, Vo2+, VCd for dye and O2 molecules, suitable oxide/redox band potentials, the modified electronic band structure especially owing to W–O1–Bi–O2–W linkages, together with high surface area endowed Bi-doped CdWO4 to form ·O2− radicals played a predominant role in the methyl orange degradation. All the experimental findings demonstrated conclusively that Bi3+ doping at Cd2+ facilitated CdWO4 to exhibit superior photocatalytic activity.