Incorporative Effect of Pt and Na₂CO₃ on TiO₂-Photocatalyzed Degradation of Phenol in Water

Abstract

Carbonate 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 Na 2 CO 3 on the TiO 2 -photocatalyzed degradation of phenol, 2,4-dichlorophenol, and H 2 O 2 in an aerated aqueous suspension at initial pH 8.0. The rate of phenol degradation, upon the addition of 2.0 mM Na 2 CO 3 , 0.52 wt% Pt, and 2.0 mM Na 2 CO 3 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 TiO 2 and Pt/TiO 2 film electrode for the photoelectrochemical oxidation of phenol, but not water. However, the rates of phenol degradation over TiO 2 and Pt/TiO 2 became decreased as carbonate concentration exceeded 5.0 and 2.0 mM, respectively. It is proposed that CO 3•− radicals are formed mainly from the hole oxidation of dicarbonate adsorbed on TiO 2 , followed by phenol degradation. At a high concentration, the CO 3•− radicals would recombine to a peroxocarbonate that easily decomposes into CO 2 and O 2 . The carbonate-mediated hole transfer from TiO 2 to phenol would incorporate with the Pt-mediated electron transfer from TiO 2 to O 2 , consequently resulting in a great improvement in the efficiency of charge separation for the reactions at interface.

CdS QDs-Decorated Self-Doped γ-Bi2MoO6: A Sustainable and Versatile Photocatalyst toward Photoreduction of Cr(VI) and Degradation of Phenol

“…The generation of • O 2 – is confirmed from the NBT (nitroblue tetrazolium chloride) test. 40 In CBBMO-3, less • O 2 – are formed compared to the neat materials, which is confirmed from the high absorbance value from Figure 16a. So, partial involvement of • O 2 – is confirmed from this NBT test.…”

Mutual influence of cupric cations and several anions in anatase and rutile TiO2 photocatalysis

“…On the other hand, many anions are efficient • OH scavengers. In the presence of SO , however, phenol oxidation on AT is increased, not decreased [27,29,48], denying the presence of • OH as well. In terms of F − effect, the hole oxidation of F − into F • (3.6 V, NHE) is unfeasible.…”

Enhanced photocatalytic oxidation of SO2 on TiO2 surface by Na2CO3 modification

“…Carbonate (CO 3 2− ) is a common and pervasive species in both aqueous and solid phases. However, there are limited studies on the effects of CO 3 2− on the photocatalytic activity of TiO 2 for environmental remediation [17]. Carbonate salts, mostly sodium carbonate, reportedly play a different role in the photocatalytic oxidation of contaminants in liquid with TiO 2 suspensions.…”

“…The addition of Na 2 CO 3 has been found to improve the PCO of aniline and phenol. [17,18] The proposed enhancement mechanisms depend on the contaminants. For the PCO of phenol, the formation of CO 3 •− from the hole oxidation of carbonate enhanced the hole transfer from TiO 2 to phenol [17].…”

“…[17,18] The proposed enhancement mechanisms depend on the contaminants. For the PCO of phenol, the formation of CO 3 •− from the hole oxidation of carbonate enhanced the hole transfer from TiO 2 to phenol [17]. An increased number of adsorption sites on TiO 2 surface and the combination of CO 3 •− and •OH were considered the main reasons behind the improvement of the photocatalytic degradation of aniline [18].…”