Ag⁰/Au⁰ nanocluster loaded Bi₂O₄ photocatalyst for methyl orange dye photodegradation

Visible-light-sensitive Ag and Au nanocluster loaded Bi₂O₄ (Ag-Bi₂O₄ and Au-Bi₂O₄) semiconductor photocatalysts have been synthesized. The composite materials exhibited increased photocatalytic degradation of the azo-dye pollutant, Methyl Orange (MO). In addition, Au-Bi₂O₄ (Au-7% wt) showed the highest MO degradation rate (0.05904 min^-1) i.e. 7.69 times higher than the pristine Bi₂O₄ and 1.4 times higher than 1% Ag-Bi₂O₄. The optical properties of the composites showed that the band gaps of the composite samples 1% Ag-Bi₂O₄ and 7% Au-Bi₂O₄ were 1.96 eV and 2.09 eV, respectively. The increase in the degradation rate is attributed to the decrease of the recombination rate of photoinduced e^-/h⁺, caused by the enhanced charge transfer between the metal nanoparticles and Bi₂O₄ as confirmed in the photocurrent measurements. The photocurrent measurements showed increase in the transients output by 8.25 times and 2.75 times for 1% Ag-Bi₂O₄ & 3% Au-Bi₂O₄, respectively as compared to that of the pristine Bi₂O₄. These features further aided the increase in the photocatalytic efficiency while retaining the original physical properties, thus showing the robustness of Bi₂O₄ as a photocatalyst.