Phenol Photodegradation on Platinized-TiO₂ Photocatalysts Related to Charge-Carrier Dynamics

Abstract

Three commercial TiO2 compounds (Degussa P25, Sachtleben UV100, and Millenium PC50) and their platinized forms have been studied by the time-resolved microwave conductivity (TRMC) method to follow their charge-carrier dynamics and to relate it to the photocatalytic activity for phenol degradation in TiO2 aqueous suspensions. The degradation reaction has been studied in detail, following the time evolution of the concentration of phenol and its intermediates by liquid chromatography. The results show that platinization has a distinct influence on the commercial compounds, decreasing globally the activity of P25 and increasing the activity of PC50 and UV100. An influence of charge-carrier lifetimes on the photoactivity of pure and platinized TiO2 samples has been evidenced.

Keggin heteropolyacid H3PW12O40 supported on different oxides for catalytic and catalytic photo-assisted propene hydration

“…The I max is lowered by the presence of the POM and the short-range decay is slightly accelerated. This indicates that the POM acts like a surface impurity, helping recombination, like in the case of the metallization, 44 but the dominant effect is the influence on the long-range decay, which is, in those three cases showed in Fig. 8(A), slowed down.…”

“…The TRMC signal gives information of the lifetimes of charge carriers created on a semiconductor by analysis of the maximum value of the signal (I max ), of the short range decay (from 0 to 40 ns) corresponding to recombination phenomena, and of the long time range decay (from 40 ns to 5 ms), corresponding to trapping phenomena. 44 Fig. 8 displays the TRMC signals obtained for some selected samples, both bare oxides and POM supported materials.…”

A review on the visible light active titanium dioxide photocatalysts for environmental applications

“…1.6) and 19 further electrochemical reduction yields H 2 O 2 (Eq. 1.7) [29,30]. These reactive oxygen 20 species may also contribute to the oxidative pathways such as the degradation of a 21 pollutant (Eq.…”

“…These reactive oxygen 20 species may also contribute to the oxidative pathways such as the degradation of a 21 pollutant (Eq. 1.8 and 1.9) [26,28,29]. 22 23 24 Recombination of photogenerated charge carriers is the major limitation in 25 semiconductor photocatalysis as it reduces the overall quantum efficiency [30].…”

Selectivity in photocatalysis by particulate semiconductors

“…A portion of these electronhole pairs diffuses out to the surface of the crystal and participates in chemical reactions with electron donors and acceptors, resulting in photocatalysis [1][2][3]. Reports on photodegradation of phenols are numerous and TiO 2 in different modifications [4] including metal-doped TiO 2 [4] and dye-sensitized TiO 2 [5], ZrO 2 [6], MoS 2 [7], WO 3 /WS 2 [8], PW 12 O 40 3- [9], α-Fe 2 O 3 [9], GdCoO 3 [10], CdSe/TiO 2 [11], In 2 O 3 /TiO 2 [12] and SnO 2 [7] are the semiconductors used as catalysts. Our experiments with sixteen semiconductors and fifteen phenols reveal that, except TiO 2 and ZnO, the other tested semiconductors are selective in degrading phenols under UV-A light; phenol degradation has been used as the standard to compare the photocatalytic efficiencies [13,14].…”