The atmospheric pressure plasma enhanced nanoparticle synthesis (APPENS) process is applied to produce nitrogen (N) doped titania (TiO2) photocatalysts. With TTIP (titanium tetraisopropoxide; Ti(OC3H7)4) and water vapors as precursors, the effect of plasma and annealing gas composition on the N-doping status is identified by a cross comparison of the chemical shift of N atoms with those of Ti and O atoms. The activities of various types of N-doped photocatalysts are evaluated via the conversion of isopropyl alcohol (IPA). The results show that the N-doped TiO2 particles with O X −Ti−N Y and −(NO) dopants are produced via N2 plasma gas followed by air or N2 annealing gases. They have better visible and UV photocatalytic activities compared to the pure TiO2 photocatalysts prepared under O2/Ar plasma and annealing gases. On the other hand, the N-doped TiO2 photocatalyst produced under N2/O2/Ar plasma gas and then annealed with pure N2 gas tends to have an additional dopant of −(NO2), but its photocatalytic activity is even worse than those of the pure TiO2 photocatalysts. The results reveal that the O X −Ti−N Y and −(NO) dopants may have positive effects on the visible light photocatalytic activity while the −(NO2) dopant tends to have a negative effect on the visible light photocatalytic activity.

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An atmospheric pressure plasma-enhanced nanoparticle synthesis (APPENS) process was proposed to produce a titania-based visible light photocatalyst. The titanium tetraisopropoxide (TTIP) precursor was vaporized with a N2 carrier gas and entered a nonthermal AC plasma system. The N2 gas was dissociated into N atoms by the plasma energy, and then they were doped into the precursor vapors. The produced TiO2 - x N x nanoparticles were highly uniform and adjustable in size. The titania-based particle sizes ranged from 25 to 40 nm, and they depended on the precursor ratio of TTIP/H2O. In addition to producing the photocatalytic particles, the APPENS process has a potential application as a continuous-flow nanosize monodisperse aerosol generator.

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