PdO loaded TiO2 hollow sphere composite photocatalyst with a high photocatalytic disinfection efficiency on bacteria

• Palladium oxide nanoparticles loaded titanium oxide hollow sphere photocatalyst.
• Largely enhanced photocatalytic disinfection of E. coli bacteria.
• Optimum PdO loading concentration at ∼0.4 wt.%.
• Enhancement attributed to both the hollow structure and the electron trapping by PdO.
• PdO is better than Pd to trap electrons because it has a larger work function than Pd.

PdO loaded TiO2 hollow spheres were synthesized via first reducing Pd2+ to Pd in ethanol onto TiO2 hollow spheres by refluxing and then oxidizing Pd to PdO through calcination in air. PdO nanoparticles were distributed relatively uniformly both on the surface and in the shell/interior of these TiO2 hollow spheres, to act as potential electron/hole pair separation centers. These PdO loaded TiO2 hollow spheres demonstrated a superior photocatalytic disinfection performance on Escherichiacoli bacteria, compared with the unloaded samples or P25 TiO2 nanoparticles. Their largely enhanced photocatalytic disinfection performance could be attributed to both their unique hollow structure and the electron trapping capability of loaded PdO nanoparticles. Samples with a series of PdO loading ratios were synthesized and tested to determine the optimum PdO loading ratio, which was found to be ∼0.4 wt.%. Below the optimum PdO loading, the photocatalytic disinfection performance increased with the increase of PdO loading ratio, while further increase of the PdO loading over 0.4% resulted in a deleterious influence on the PdO enhancement effect. The photocatalytic performance differences between Pd and PdO modified samples were also investigated. Samples with 0.4% PdO modification demonstrated a better photocatalytic disinfection effect on E. coli bacteria than samples with 0.4% Pd modification, which could be attributed to their different work functions.

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