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.
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