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Incorporative Effect of Pt and Na2CO3 on TiO2‑Photocatalyzed Degradation of Phenol in Water
journal contribution
posted on 2016-10-27, 00:00 authored by Xianqiang Xiong, Xiao Zhang, Yiming XuCarbonate anions
are often present in aqueous solution, but their
effect on the semiconductor-photocatalyzed reaction has been rarely
studied. In this work, we report a positive effect of Na2CO3 on the TiO2-photocatalyzed degradation
of phenol, 2,4-dichlorophenol, and H2O2 in an
aerated aqueous suspension at initial pH 8.0. The rate of phenol degradation,
upon the addition of 2.0 mM Na2CO3, 0.52 wt%
Pt, and 2.0 mM Na2CO3 plus 0.52 wt % Pt, was
increased by 1.78, 3.38, and 6.63 times, respectively. Such positive
effect of carbonate was also observed from a TiO2 and Pt/TiO2 film electrode for the photoelectrochemical oxidation of
phenol, but not water. However, the rates of phenol degradation over
TiO2 and Pt/TiO2 became decreased as carbonate
concentration exceeded 5.0 and 2.0 mM, respectively. It is proposed
that CO3•– radicals are formed
mainly from the hole oxidation of dicarbonate adsorbed on TiO2, followed by phenol degradation. At a high concentration,
the CO3•– radicals would recombine
to a peroxocarbonate that easily decomposes into CO2 and
O2. The carbonate-mediated hole transfer from TiO2 to phenol would incorporate with the Pt-mediated electron transfer
from TiO2 to O2, consequently resulting in a
great improvement in the efficiency of charge separation for the reactions
at interface.