Visible Light Active Platinum-Ion-Doped TiO₂ Photocatalyst

Abstract

Platinum-ion-doped TiO2 (Pt(ion)-TiO2) was synthesized by a sol-gel method, and its visible light photocatalytic activities were successfully demonstrated for the oxidative and reductive degradation of chlorinated organic compounds. Pt(ion)-TiO2 exhibited a yellow-brown color, and its band gap was lower than that of undoped TiO2 by about 0.2 eV. The flat band potential of Pt(ion)-TiO2 was positively shifted by 50 mV compared with that of undoped TiO2. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyses showed that the Pt ions substituted in the TiO2 lattice were present mainly in the Pt(IV) state with some Pt(II) on the sample surface. Pt(ion)-TiO2 exhibited higher photocatalytic activities than undoped TiO2 under UV irradiation as well. The visible light activity of Pt(ion)-TiO2 was strongly affected by the calcination temperature and the concentration of Pt ion dopant, which were optimal at 673 K and 0.5 atom %, respectively. Under visible irradiation, Pt(ion)-TiO2 degraded dichloroacetate and 4-chlorophenol through an oxidative path and trichloroacetate via a reductive path. The activity of Pt(ion)-TiO2 was not reduced when used repeatedly under visible light. However, visible-light-illuminated Pt(ion)-TiO2 could not degrade substrates such as tetramethylammonium and trichloroethylene, which are degraded with UV-illuminated TiO2. The characteristics and reactivities of Pt(ion)-TiO2 as a new visible light photocatalyst were investigated in various ways and discussed in detail.

Photocatalytic production of hydrogen on Ni/NiO/KNbO3/CdS nanocomposites using visible light

“…However, the majority of the simple and mixed-metal oxides photocatalysts are primarily active for H 2 production under UV irradiation (l < 385 nm or E g $ 3.0 eV) present in only a small portion of solar light. More recently, there is a focused effort on the development of photocatalysts that are capable of using visible light (l ¼ 400-700 nm) for the photocatalytic production of H 2 including transition metal doping (e.g., platinum, 29 chromium, 30 and vanadium 31 ) and nonmetallic element doping (e.g., nitrogen, [32][33][34][35] sulfur, 36,37 and carbon 35,38 ). CdS, n-type semiconductor with E g ¼ 2.4 eV, has been shown to have photocatalytic activity for H 2 production under visible light irradiation, although, sacrificial electron donors such as C 2 H 5 OH, 39 HS À , 40,41 or SO 3 2À 19 are used to obtain measurable rates of H 2 production and to avoid the photocorrosion of CdS in the presence of O 2 .…”

Parameters affecting the photocatalytic degradation of dyes using TiO2: a review

“…Heterogeneous catalysis has been successfully employed for the degradation of various families of hazardous materials. Titanium dioxide (TiO 2 ), due to its non-toxic, inexpensive, and high reactive nature, has been extensively investigated as a heterogeneous photocatalyst for the remediation of contaminated environment (Hassan et al 2014;Harbi et al 2015;Kim et al 2005). The advantage of TiO 2 as photocatalyst is that organic pollutants are usually completely mineralized to non-toxic substances such as CO 2 , HCl and water and thus the reactions do not suffer the drawbacks of photolysis reactions in terms of the production of intermediate products.…”

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

“…Noble metals act as passive sinks for electrons to promote the interfacial charge transfer process and enhance the quantum efficiency of photocatalytic system [29,[236][237][238]. In addition, metal nanoparticles show plasmonic effects and provide hot electrons into the conduction band of titania.…”