A photocatalytic superhydrophobic coating with p–n type BiOBr/α-Fe₂O₃ heterojunctions applied in NO degradation

Coal combustion generates soot-type air pollution, and NO, as a typical pollutant, is the main haze-causing pollutant. The degradation of NO by means of photocatalytic superhydrophobic multifunctional coatings is both durable and economical. The precipitation method was employed to create a p-n type BiOBr/α-Fe₂O₃ photocatalytic binary system. BiOBr/α-Fe₂O₃ nanoparticles were combined with polydimethylsiloxane (PDMS) in a butyl acetate solution to produce a BiOBr/α-Fe₂O₃/PDMS/butyl acetate emulsion, and photocatalytic superhydrophobic coatings were then prepared using a one-step cold-spraying method. Photocatalytic oxidation experiments were conducted using a low concentration of NO as the targeted degradant. The results indicate that BiOBr/α-Fe₂O₃ photocatalytic heterojunctions were successfully prepared with NO removal up to 65%, indicating that the formation of p-n type heterojunctions enhances the light absorption range and improves the separation of photogenerated charge carriers. Furthermore, when the mass ratio of photocatalytic material to PDMS is 30 : 1, the photocatalytic superhydrophobic coating exhibits optimal performance, attaining a contact angle of 159.55° and NO degradation rate of 70.9%. The study also found that the photocatalytic superhydrophobic coating remained stable after undergoing cyclic degradation, acid and alkali resistance tests, and self-cleaning tests. The mechanism of photocatalytic superhydrophobic coatings was further explored, which provided new insights and a theoretical foundation for the development of self-cleaning urban environments.