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.
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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