Preparation of N-doped TiO2 photocatalyst by atmospheric pressure plasma process for VOCs decomposition under UV and visible light sources

The nitrogen doped (N-doped) titanium dioxide (TiO₂) photocatalyst was prepared by the atmospheric-pressure plasma-enhanced nanoparticles synthesis (APPENS) process operated under normal temperature, i.e. the dielectric barrier discharge plasma process. The N₂ carrier gas is dissociated in the AC powered nonthermal plasma environment and subsequently doped into the TiO₂ photocatalyst that was capable of being induced by visible light sources. The APPENS process for producing N-doped TiO₂ showed a higher film deposition rate in the range of 60–94 nm/min while consuming less power (<100 W) as compared to other plasma processes reported in literatures. And the photocatalytic activity of the N-doped TiO₂ photocatalyst was higher than the commercial ST01 and P25 photocatalysts in terms of toluene removals in a continuous flow reactor. The XPS measurement data indicated that the active N doping states exhibited N 1s binding energies were centered at 400 and 402 eV instead of the TiN binding at 396 eV commonly observed in the literature. The light absorption in the visible light range for N-doped TiO₂ was also confirmed by a clear red shift of the UV-visible spectra.