Ceria doped TiO₂ as photocatalyst for water treatment under visible light

Abstract

The photocatalytic activity of bare titania and ceria supported mesoporous titania (CeO2/TiO2) catalysts were assessed for the degradation of caffeine by visible light irradiation in absence of the oxidants. Different wt% metal loaded (bare, 0.1, 0.5 and 1.0) materials were synthesised by a sol-gel method using anionic surfactants. Various instrumentation techniques were used to characterise the prepared photo-catalysts such as P-XRD, BET, TEM, SEM-EDX, FT-IR, Raman, UV-DRS and photoluminescence spectroscopy. 0.5% CeO2 doped titania exhibited excellent efficiency in photo degradation of caffeine in aqueous solution relative to all the other prepared heterogeneous catalysts. All the materials showed good efficiency and were recyclable without loss of catalytic activity up to three times. Analysis of degradation products was carried by Liquid chromatograph-mass spectrometry. Two reaction products 6-amino-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetradropymidin-5-ly)-methylcarbamic acid (ATCA) and N-methyl-N-(methylcarbomoyl)-2-oxoacetamide (MMO) were positively identified.

Photocatalytic dye-degradation activity of nano-crystalline Ti1−xMxO2−δ (M =Ag, Pd, Fe, Ni and x = 0, 0.01) for water pollution abatement

“…The PL spectra were recorded at an excitation wavelength of 290 nm which shows a broad band with multiple superimposed peaks nearly at $380, 415, 480, and 523 nm. [48][49][50][51][52][53] The rst emission peak around $380 nm was observed for all the combustion synthesized TiO 2 photocatalysts which is attributed to direct recombination of the electron-hole which is larger than the forbidden gap (as TiO 2 is an indirect gap semiconductor). 48 The emission peak at $415 nm is attributed to the indirect band gap partially allowed electronic transition, [50][51][52] while the peaks at $480 and 523 nm arise due to shallow trapped surface states such as Ti 4+ -OH or oxygen vacancies.…”

“…48 The emission peak at ∼415 nm is attributed to the indirect band gap partially allowed electronic transition, 50–52 while the peaks at ∼480 and 523 nm arise due to shallow trapped surface states such as Ti 4+ –OH or oxygen vacancies. 50,53 It was noticed that upon metal ion doping the emission intensity decreases which indicates the lower recombination rate of the charge carriers. In the case of Fe 3+ and Ni 2+ doped TiO 2 , the decrease in the PL intensity can be attributed to the electron transfer from the conduction band of Ti 4+ to the new levels introduced by partially filled 3d metal ions.…”