Tuning Effect of N2 on Atmospheric-Pressure Cold Plasma CVD of TiO2 Photocatalytic Films

To deposit TiO2 films through plasma CVD, the partial pressure ratio of O-2 to TiCl4 should be greater than the stoichiometric ratio (p(O2)/p(TiCl4) > 1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N-2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O-2 (p(O2)/p(TiCl4) = 2.6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N-2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N-2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N-2 is further discussed.