Positively and Negatively Charged Double Shell with Au Sandwich for Protecting and Enhancing Photocatalytic Activity of TiO2-Based Photocatalyst

Enhancing selectivity and high affinity between a photocatalyst and target pollutants, preventing photocatalytic poisoning from degradation intermediates, and improving photocatalytic performance are three challenges for a heterogeneous photocatalyst that can be unlocked by a positively and negatively charged double shell with a Au sandwich. At pH 4.0, Ta2O5 and TiO2 shells are positively and negatively charged, respectively. Cationic dyes (Rhodamine B (RhB)) and double shelled Ta2O5@ Au@TiO2 hollow spheres are chosen for a proof-of-concept study. The photocatalytic activity is in the order of double shelled Ta2O5@Au@TiO2 hollow spheres > Ta2O5 hollow spheres > TiO2 hollow spheres. The photocatalytic performance of double shelled Ta2O5@Au@TiO2 hollow spheres benefits from hollow spheres avoiding the reunion and more diverse heterophase junctions than Ta2O5, TiO2, and Au. Impressively, by electrostatic attraction and repulsion, cationic RhB is selectively enriched onto the negatively charged Ta2O5 shell, and then, RhB and an intermediate are excluded into the positively charged inner TiO2 shell, i.e., the poisoning on TiO2 is avoided. Au is embedded in the middle to promote the transmission of photogenerated electrons, which is helpful to decompose the intermediates and RhB, so the poisoning on Ta2O5 can be relieved.

Automated summary

The positively and negatively charged double shell with a Au sandwich can enhance selectivity, prevent photocatalytic poisoning, and improve performance of a heterogeneous photocatalyst. The proof-of-concept study using Ta2O5@Au@TiO2 hollow spheres showed that the photocatalytic activity is significantly higher compared to Ta2O5 and TiO2 hollow spheres, benefiting from the diverse heterophase junctions and avoidance of poisoning.