Effect of Plasma Processing Gas Composition on the Nitrogen-Doping Status and Visible Light Photocatalysis of TiO2

The atmospheric pressure plasma enhanced nanoparticle synthesis (APPENS) process is applied to produce nitrogen (N) doped titania (TiO 2 ) photocatalysts. With TTIP (titanium tetraisopropoxide; Ti(OC 3 H 7 ) 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 TiO 2 particles with O X −Ti−N Y and −(NO) dopants are produced via N 2 plasma gas followed by air or N 2 annealing gases. They have better visible and UV photocatalytic activities compared to the pure TiO 2 photocatalysts prepared under O 2 /Ar plasma and annealing gases. On the other hand, the N-doped TiO 2 photocatalyst produced under N 2 /O 2 /Ar plasma gas and then annealed with pure N 2 gas tends to have an additional dopant of −(NO 2 ), but its photocatalytic activity is even worse than those of the pure TiO 2 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 −(NO 2 ) dopant tends to have a negative effect on the visible light photocatalytic activity.