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 (V0o, V_o¹⁺, V_o²⁺) along with cadmium vacancies () in Bi-doped CdWO₄. The coexistence and synergy of more adsorption sites of V0o, V_o¹⁺, V_o²⁺, V_Cd 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.