Dual function of H₂O on interfacial intermediate conversion and surface poisoning regulation in simultaneous...

Co-existing air pollutants, especially NO_x and VOCs, will generate secondary photochemical pollution under light irradiation. However, simultaneous elimination of multi-pollutants has long been a challenge. Photocatalysis could turn the reaction pathway between pollutants to convert them into harmless products, which is a promising technology for multi-pollutant control. Here we achieved synergistic photocatalytic degradation of NO and C₇H₈ on InOOH photocatalyst, and the performance can be adjusted by H₂O through affecting the interaction between surface species and catalyst. In situ DRIFTS and GC-MS revealed that the improved efficiency originated from the fast conversion of C-N coupling intermediates led by additional H₂O. Surface characterizations and DFT simulation determined that accumulated nitrates will compete with the adsorption of NO and C₇H₈, resulting in a decline in efficiency in the later stage. Although improved efficiency would bring more nitrates, as H₂O has comparable adsorption to nitrate at the same site, high humidity can mitigate the deactivation. The photocatalyst can be also simply regenerated by water washing. This work reveals the complex interaction in the multi-pollutant system and provides guidelines for precisely regulating the synergistic removal of NO_x and VOCs.