title: Sol-gel synthesis of mesoporous anatase-brookite and anatase-brookite-rutile TiO2 nanoparticles and their photocatalytic properties.
abstract: TiO2 photocatalysts with a mixture of different TiO2 crystal polymorphs have customarily been synthesized hydrothermally at high temperatures using complicated and expensive equipment. In this study TiO2 nanoparticles with a mixture of TiO2 crystals were synthesized using a modified sol-gel method at low temperature. In order to form nanoparticles with different polymorphs a series of samples were obtained at pH 2, 4, 7 and 9. Raw samples were calcined at different temperatures ranging from 200 to 800°C to evaluate the effect of the calcination temperature on the physico-chemical properties of the samples. XRD results revealed that a mixture of anatase and brookite can be obtained in the as-synthesized samples and in those calcined up to 800°C depending on the pH used to obtain the final product. Indeed, a mixture of anatase brookite and rutile; or a sample with only rutile phase can be yielded through further calcination of the as-prepared samples at temperatures ⩾600°C due to phase transformation. The photocatalytic performance of the samples with a mixture of anatase-brookite; anatase-brookite-rutile; and anatase-rutile (Degussa P25 TiO2) was exquisitely investigated in the degradation of methylene blue solutions. The samples obtained at pH 2 and calcined at 200°C possessed the highest activity of all due to its superior properties. This study elucidates a facile method suitable for the synthesis of TiO2 with different mixtures of TiO2 polymorphs with desirable properties for various applications.
authors.affiliation: Department of Materials Science and Engineering, Kangwon National University, Samcheok-si, 271 Kangwon-do, Republic of Korea; School of Chemistry, University of Witswatersrand, Johannesburg WITS 2050, South Africa.
authors.forename: Bridget K
authors.initials: BK
authors.lastname: Mutuma
authors.affiliation: Department of Chemical Engineering, Hanyang University, 1271 Sa 3 dong, Sangnok-gu, Ansan-si, Gyeongi-do 426-791, Republic of Korea; Department of Chemistry, Mkwawa College, University of Dar es Salaam, Iringa, United Republic of Tanzania. Electronic address: shaogod@gmail.com.
authors.forename: Godlisten N
authors.initials: GN
authors.lastname: Shao
authors.affiliation: Department of Materials Science and Engineering, Kangwon National University, Samcheok-si, 271 Kangwon-do, Republic of Korea.
authors.forename: Won Duck
authors.initials: WD
authors.lastname: Kim
authors.affiliation: Department of Chemical Engineering, Hanyang University, 1271 Sa 3 dong, Sangnok-gu, Ansan-si, Gyeongi-do 426-791, Republic of Korea.
authors.forename: Hee Taik
authors.initials: HT
authors.lastname: Kim
keywords: Anatase–brookite TiO(2); Heterogeneous catalysis; Photocatalysis; Sol–gel method