High-humidity tolerance of porous TiO2(B) microspheres in photothermal catalytic removal of NOx

Semiconductor oxides are widely used to achieve photocatalytic removal of NO x (NO and NO 2 ) species. These materials also exhibit enhanced oxidation ability in thermally assisted photocatalysis ; however, many of them tend to be deactivated at high relative humidity (RH) levels. In the case of the benchmark P25 TiO 2 photocatalyst, we observe a significant decrease in non-NO 2 selectivity from 95.02% to 58.33% when RH increases from 20% to 80%. Interestingly, the porous TiO 2 (B) microspheres synthesized in this work exhibit 99% selectivity at 20% RH; the selectivity remains as high as 96.18% at 80% RH. The high humidity tolerance of the TiO 2 (B) sample can be ascribed to its strong water desorption capacity and easy O 2 adsorption at elevated temperatures, which reflects the fact that the superoxide radical is the main active species for the deep oxidation of NO x . This work may inspire the design of efficient photothermal catalysts with application in NO x removal in hot and humid environments.