Investigation of Advanced Oxidation Process in the Presence of TiO2 Semiconductor as Photocatalyst: Property, Principle, Kinetic Analysis, and Photocatalytic Activity

Abstract

Water pollution is considered a serious threat to human life. An advanced oxidation process in the presence of semiconductor photocatalysts is a popular method for the effective decomposition of organic pollutants from wastewater. TiO2 nanoparticles are widely used as photocatalysts due to their low cost, chemical stability, environmental compatibility and significant efficiency. The aim of this study is to review the photocatalytic processes and their mechanism, reaction kinetics, optical and electrical properties of semiconductors and unique characteristics of titanium as the most widely used photocatalyst; and to compare the photocatalytic activity between different titania phases (anatase, rutile, and brookite) and between colorful and white TiO2 nanoparticles. Photocatalytic processes are based on the creation of electron–hole pairs. Therefore, increasing stability and separation of charge carriers could improve the photocatalytic activity. The synthesis method has a significant effect on the intensity of photocatalytic activity. The increase in the density of surface hydroxyls as well as the significant mobility of the electron–hole pairs in the anatase phase increases its photocatalytic activity compared to other phases. Electronic and structural changes lead to the synthesis of colored titania with different photocatalytic properties. Among colored titania materials, black TiO2 showed promising photocatalytic activity due to the formation of surface defects including oxygen vacancies, increasing the interaction with the light irradiation and the lifetime of photogenerated electron–hole pairs. Among non-metal elements, nitrogen doping could be effectively used to drive visible light-activated TiO2.

Role of Surface Chemistry in Pyrrole Autoxidation

“…The VBM of TiO 2 is 2.6–2.8 V vs NHE , and MoCl 5 exhibits an oxidation potential of 3.34 V vs NHE, providing a sufficient thermodynamic driving force for MoCl 5 to oxidize TiO 2 . While Al 2 O 3 has a lower VBM position of >5 V vs NHE , and is therefore not expected to be susceptible to oxidation by MoCl 5 , ZnO and TiO 2 have comparable VBM positions , of <3 V vs NHE as indicated in Figure b above. Therefore, if MoCl 5 has sufficient oxidation strength to oxidize TiO 2 , one would expect MoCl 5 to also oxidize ZnO.…”

Photocatalytic Degradation of Pharmaceutical Residues from Water and Sewage Effluent Using Different TiO2 Nanomaterials

“…Secondly, the photodegradation was most effective with Degussa P25, followed by Hombikat 100 TiO 2 , and finally by Aldrich TiO 2 , suggesting the critical role of the crystal structure on the photocatalytic activity of TiO 2 . Notably, Degussa P25 TiO 2 consists of anatase and rutile phases and is generally known as a benchmark photocatalyst [ 25 ]. Thirdly, the photocatalysis was most efficient when the photocatalyst dosage was 150 mg L −1 .…”

“…Various metal oxides such as Ga 2 O 3 [ 12 ], ZnO [ 13 , 14 ], TiO 2 [ 15 , 16 , 17 ], and In 2 O 3 [ 18 ], polymeric materials such as g-C 3 N 4 [ 19 , 20 , 21 , 22 ], and spinel structures such as CuFe 2 O 4 [ 23 ] and ZnFe 2 O 4 [ 24 ] have been used in photocatalysis technology. Notably, TiO 2 is generally regarded as the benchmark photocatalyst [ 25 ]. It has the advantages of abundancy, structural diversity, and high chemical stability [ 26 ].…”

Enhanced efficiency of photocatalytically synthesised Co3+/Co2+-incorporated CeO2/SnO2 nanocomposite and supercapacitor studies

“…SnO 2 -based photocatalysts gained the most attention because of their unique properties of high photo-oxidization, photostability, low cost, and non-toxicity. 3 SnO 2 and CeO 2 coupling can transfer specific electrons and holes from SnO 2 and CeO 2 , simplifying electron–hole pair separation and increasing the photocatalytic activity of hybrid photocatalysts. 4 Heavy metal contamination is the most important environmental issue.…”