Uniform titania-supported Ce() carbonate cluster catalysts for degradation of reactive oxygen species

We report the synthesis of uniform 2.5 ± 0.4 nm diameter Ce( iii ) carbonate clusters deposited on the surface of TiO 2 nanoparticles and characterize them using HAADF-STEM and EELS, as well as UV-Vis and FTIR spectroscopies. This material is a highly proficient catalytic antioxidant for the degradation of photocatalytically generated reactive oxygen species (ROS). We observed an unusual U-shaped pH-dependence in its photoprotection catalytic activity, with an optimum function in the near-neutral pH range of 7.7 ± 0.7. This sharp pH dependence is not observed in previously reported bulk Ce( iii ) carbonate materials, and it is also not a consequence of Ce( iii ) carbonate cluster decomposition. However, it is consistent with a tandem reaction sequence consisting of a biomimetic superoxide dismutase and catalase function, which is dependent on a balance of protons and hydroxide anions for function. Our dissolution-deposition approach for synthesizing nanoscale Ce( iii ) carbonate clusters on TiO 2 should be generalizable to other carbonates and metal-oxide supports. Uniform 2.5 nm Ce( iii ) carbonate clusters on TiO 2 function as ROS degradation catalysts, consistent with a superoxide dismutase-catalase tandem reaction mechanism.