Transformation of hydrogen titanate nanoribbons to TiO₂ nanoribbons and the influence of the transformation strategies on the photocatalytic performance

Abstract

SummaryThe influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i) through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400–650 °C, (ii) through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii) through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g)/Ar(g) flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti4+ to Ti3+. The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the hydrothermally derived TiO2 NRs was additionally improved by a subsequent heat treatment in air.

Bicrystalline TiO2 heterojunction for enhanced organic photodegradation: engineering and exploring surface chemistry

“…8a, un-treated TiAR showed a strong signal at g ¼ 2.01 and a broad peak at g ¼ 1.981, which were ascribed to V O and unsaturated Ti 3+ , respectively. [47][48][49] For TiAR(H 2 ), an extra new peak for Ti 3+ (g ¼ 1.999) appeared, and the peak intensity for V O increased slightly. This result indicated that H 2 treatment led to the formation of more Ti 3+ /V O on TiAR(H 2 ), which was consistent with literature reports.…”

“…First, TiAB had multiple peaks at g ¼ 1.971-1.991, g ¼ 2.007, and g ¼ 2.023, which were attributed to Ti 3+ sites, V O and super-oxygen ions (O 2 À ), respectively. 47,[49][50][51] The formation of O 2 À species was possibly due to the attachment of electrons stored in V O to adsorbed O 2 molecules. Second but more importantly, the intensity of Ti 3+ on TiAB was much stronger than that on TiAR, indicating TiAR had a higher content of Ti 3+ .…”

Photocatalytic Activity of Nanostructured Titania Films Obtained by Electrochemical, Chemical, and Thermal Oxidation of Ti6Al4V Alloy—Comparative Analysis

“…It is because of the fact, that surface wettability and surface energy, which influence mentioned activity, are closely related to surface morphology. Among different titania architectures nanoparticles [38,39], nanotubes [40,41], nanofibers [42], nanowires [43], nanorods [43,44], nanobelts [43,45], nanoribbons [46], are the most important and often studied. The diversity of TiO 2 nanoarchitecture results from a wide range of applied experimental methods for the synthesis of nanomaterials.…”

Sulfur-, nitrogen- and platinum-doped titania thin films with high catalytic efficiency under visible-light illumination

“…After polymer decomposition via thermal treatment, mesoporous materials with high surface area and pore volume are obtained [ 13 – 15 ]. The increase in surface area depends on the type of polymer added, the type of oxides and on the stage of synthesis during which the polymer is added [ 16 – 18 ]. The specific surface area can also be increased by decreasing the particle size of TiO 2 ; however, it has been shown that the photocatalytic activity does not monotonically increase with decreasing particle size, but rather there exists an optimal particle size for pure nanocrystalline TiO 2 [ 19 ].…”