Multi-approach Electron Paramagnetic Resonance Investigations of UV-Photoinduced Ti³⁺in Titanium Oxide-Based Gels

Abstract

EPR investigations of the photoreduction of Ti(4+) into Ti(3+) under UV irradiation were carried out on three titanium-based materials for which the initial concentration of Ti(4+) was defined in the ternary phase diagram (TiOCl(2), H(2)O, DMF). The kinetics of this photoreduction was monitored at 200 K and related to the initial concentration of Ti(4+) in the solution. This study was complemented by a multi-approach EPR method (pulsed electron paramagnetic resonance (EPR), pulsed electron nuclear double resonance, and hyperfine sublevel correlation spectroscopy (HYSCORE)) with the aim of probing the proton environment of the Ti(3+) ions. Indeed, many species such as H(2)O, OH(-), HCOO(-) are located in the immediate vicinity of Ti(3+). Although we found that a distribution of g tensors was involved, for simplicity, two types of g tensor were used to describe the main features of the EPR signal related to the paramagnetic ions. Additionally, we have evidenced that two kinds of protons are identified next to Ti(3+) species, with specific distances determined from the hyperfine coupling parameters obtained by the HYSCORE method.

Mechanochemical synthesis of nanostructured BiVO4 and investigations of related features

“…This is achieved notably by doping the material by suitable elements which will be able to induce intermediate levels in the band gap [4]. An alternative approach can be also searched through the use of photoactive titanium oxide based gels [5]. However, the search for intrinsically active and stable materials represent challenging tasks and this is the motivation of our present work to offer an alternative PC active materials based on nanostructured bismuth.…”

Modulating catalytic oxygen activation over Pt–TiO2/SiO2 catalysts by defect engineering of a TiO2/SiO2 support

“…The broad peak at a g value of 1.935 corresponds to the presence of paramagnetic Ti 3+ centers associated with oxygen vacancies. 31 The peak with a g -factor of 2.002 can be attributed to E ′ center defects. 32,33 For the Pt/SiO 2 sample, only the E ′ center defect peak was detected.…”

Molten salt construction of stable oxygen vacancies on TiO2 for enhancement of visible light photocatalytic activity

“…In contrast, a prominent signal at g ¼ 1.93-1.98 appears in B-TiO 2 , demonstrating the presence of Ti 3+ in the bulk. 16 The shoulder peak at g ¼ 2.001 conrms the surface oxygen vacancies. 17 The formation mechanism of oxygen vacancies or Ti 3+ is explained as followed: when TFA modied P25 was calcinated in MS, the thermal decomposition of TFA was suppressed by the oxygen isolation effect of LiCl-KCl eutectic mixture and the incomplete combustion production of TFA, such as CO, consumed the lattice oxygen in TiO 2 quickly, leading to the formation of amount of oxygen vacancies on the surface and in the bulk of TiO 2 .…”