TiO2 photocatalyst for removal of volatile organic compounds in gas phase – A review

Abstract

Heterogeneous photocatalytic oxidation process (PCO) is a promising technology for removing indoor volatile organic compounds (VOCs) contaminants. Titanium dioxide (TiO 2 ) has been regarded as the most suitable photocatalyst for its cost effectiveness, high stability and great capability to degrade various VOCs. However, no TiO 2 -based photocatalysts completely satisfy all practical requirements given photoexcited charge carriers' short lifetime and a wide band gap requiring ultraviolet (UV) radiation. Strategies for improving TiO 2 photocatalyst activities by doping with different metal and/or non-metal ions and by coupling with other semiconductors have been examined and reported. These techniques can improve PCO performance through the following mechanisms: i) by introducing an electron capturing level in the band gap that would generate some defects in the TiO 2 lattice and help capture charge carriers; ii) by slowing down the charge carrier recombination rate and increasing VOCs degradation. This paper reports the outcomes of a comprehensive literature review of TiO 2 modification techniques that include approaches for overcoming the inherent TiO 2 limitations and improving the photocatalytic degradation of VOCs. Accordingly, it focuses on the recent development of modified-TiO 2 used for degrading gas phase pollutants in ambient conditions. Modification techniques, such as metal and non-metal doping, co-doping, and the heterojunction of TiO 2 with other semiconductors, are reviewed. A brief introduction on the basics of photocatalysis and the effects of controlling parameters is presented, followed by a discussion about TiO 2 photocatalyst modification for gas phase applications. The reported experimental results obtained with PCO for eliminating VOCs are also compiled and evaluated.

EPR Investigations of G-C3N4/TiO2 Nanocomposites

“…Before exposure, the X-and Q-band EPR spectra of samples M1-M6 correspond to the signal of the conduction electrons in the localized π-states in g-C 3 The ability of photocatalysts dispersed in water or DMSO to generate non-persistent radical species was tested by spin trapping technique and reduction of semi-stable ABTS •+ . The results of EPR spin trapping experiments in aqueous suspensions showed that paramagnetic species formed upon the exposure of dispersed g-C 3 N 4 /TiO 2 nanopowders sensitively reflect the initial weight ratio of annealed melamine/TiO 2 , and the decrease in nitrogen-content in the synthesized photocatalysts M4-M6 is coupled with significant activity upon UV exposure and limited VIS-light activity.…”

“…Stability, low cost, relatively low toxicity, and suitable photocatalytic activity predispose TiO 2 to applications in various areas (gas sensors, photocatalysts, solar cells, etc.) [1][2][3][4]. However, TiO 2 has several limitations as a photocatalyst; the rapid recombination of photogenerated holes and electrons in the nanosecond scale inhibits the required consecutive reactions of the charge carriers on surface.…”

Effects of Particle Size on the Structure and Photocatalytic Performance by Alkali-Treated TiO2

“…However, large band gap of TiO 2 and high electron hole recombination limit its photocatalytic performance [4]. To modify these intrinsic drawbacks, tremendous efforts have been devoted to broadening the active spectrum and promoting the charge transport [5,6].…”

Gas‐phase removal of indoor volatile organic compounds and airborne microorganisms over mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide nanocomposites

“…In order to improve air quality, many techniques including adsorption on carbon, 4 glass 5 and polymeric materials, 6 application of bioelectrochemical system, 7 photocatalytic degradation process, 8,9 condensation, membrane separation, 10 separation of VOCs using ionic liquids, 11 thermal oxidation process, and catalytic combustion 12 have been studied. Among them, photocatalytic oxidation is one of the most promising technique for air purification.…”

“…process, 8,9 condensation, membrane separation, 10 separation of VOCs using ionic liquids, 11 thermal oxidation process, and catalytic combustion 12 have been studied. Among them, photocatalytic oxidation is one of the most promising technique for air purification.…”