Graphitic Layered Structures Enhancing TiNT Catalyst Photo-Electrochemical Behaviour

The increasing knowledge in nanoscience and materials technology promoted the development of advanced materials with enhanced and unusual properties suitable for sustainable applications ranging from energy to environmental purposes. Here are presented some results from our current investigations on composite semiconducting materials. The investigated composites have been prepared from different nitrogen precursors and thin films of TiO2 nanotubes. The synergy between hetero-structures based on graphitic-C3N4 and thin films of titania nanotubes obtained by anodisation was studied. The composites have been characterised with several complementary techniques to evidence the relation between photo-behaviour and the composition of the samples. This study allows new insights into the nature of the specific enhanced properties due to this synergy among the two compounds. The g-C3N4/TiNT heterojunctions showed enhanced photo-electrochemical properties observed from the photocurrent measurements. The as-prepared composites have been investigated as cathode materials in the electrocatalytic reduction of oxalic acid (OX), evidencing the capability of tuning the reaction toward glycolic acid with respect to the pristine TiNT array. The observed Faradic efficiency (FE) for the composites follows the trend: TiNT-U6 > TiNT-M6 > TiNT-MU18. TiNT-U6 shows the best performances (FEGC = 63.7%; FEGO = 15.5%; OX conversion = 61. 4%) after 2 h of reaction. The improved photo-electrochemical properties make these materials suitable for H2 production, solar-light-driven water splitting, and CO2 reduction applications

Graphitic Layered Structures Enhancing TiNT Catalyst Photo-Electrochemical Behaviour

The increasing knowledge in nanoscience and materials technology promoted the development of advanced materials with enhanced and unusual properties suitable for sustainable applications ranging from energy to environmental purposes. Here are presented some results from our current investigations on composite semiconducting materials. The investigated composites have been prepared from different nitrogen precursors and thin films of TiO2 nanotubes. The synergy between hetero-structures based on graphitic-C3N4 and thin films of titania nanotubes obtained by anodisation was studied. The composites have been characterised with several complementary techniques to evidence the relation between photo-behaviour and the composition of the samples. This study allows new insights into the nature of the specific enhanced properties due to this synergy among the two compounds. The g-C3N4/TiNT heterojunctions showed enhanced photo-electrochemical properties observed from the photocurrent measurements. The as-prepared composites have been investigated as cathode materials in the electrocatalytic reduction of oxalic acid (OX), evidencing the capability of tuning the reaction toward glycolic acid with respect to the pristine TiNT array. The observed Faradic efficiency (FE) for the composites follows the trend: TiNT-U6 > TiNT-M6 > TiNT-MU18. TiNT-U6 shows the best performances (FEGC = 63.7%; FEGO = 15.5%; OX conversion = 61. 4%) after 2 h of reaction. The improved photo-electrochemical properties make these materials suitable for H2 production, solar-light-driven water splitting, and CO2 reduction applications

Photoactive titania nanostructured thin films: Synthesis and characteristics of ordered helical nanocoil array

Titania nanostructured thin films have been prepared by anodization of titanium foils at different voltages in the 10–20 V range. They have been characterized by field emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), UV–vis diffuse reflectance and current–time transients during the anodization process. The observed nanostructure differs from that reported for titania nanotubes (hollow columns) and can be described as helical nanocoils which form an ordered array over the entire surface. The model of formation of these nanostructures (TNT) has been also proposed. The voltage applied during the anodization influences the mean dimension of these TNT, their wall thickness and also their degree of packing. A linear relationship between the wall thickness, in the 5–10 nm range, and the band gap is observed. The behavior of these samples in the photo-generation of current by irradiation with a low-power lamp simulating solar spectrum has been also studied. A main factor which determine with photo-behavior is the band gap which in turn depends on the characteristics of the TNT. Increasing the voltage during anodization increases the wall thickness and the band gap shifts toward visible region with an improvement of the photo-generated current density. It is also demonstrated that the formation of these helical nanocoils improve the photo-generated current with respect to the sample samples after short anodization where only a titania layer is formed

Photoactive materials based on semiconducting nanocarbons - A challenge opening new possibilities for photocatalysis

This perspective paper introduces the concept that nanocarbons and related materials such as carbon dots are an interesting intrinsic photocatalytic semiconducting material, and not only a modifier of the existing (semiconducting) materials to prepare hybrid materials. The semiconducting properties of the nanocarbons, and the possibility to have the band gap within the visible-light region through defect band engineering, introduction of light heteroatoms and control/manipulation of the curvature or surface functionalization are discussed. These materials are conceptually different from the "classical" semiconducting photocatalysts, because semiconductor domains with tuneable characteristics are embedded in a conductive carbon matrix, with the presence of various functional groups (as C=0 groups) enhancing charge separation by trapping electrons. These nanocarbons open a range of new possibilities for photocatalysis both for energetic and environmental applications. The use of nanocarbons as quantum dots and photo luminescent materials was also analysed. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved

Photoactive materials based on semiconducting nanocarbons-A challenge opening new possibilities for photocatalysis

This perspective paper introduces the concept that nanocarbons and related materials such as carbon dots are an interesting intrinsic photocatalytic semiconducting material, and not only a modifier of the existing (semiconducting) materials to prepare hybrid materials. The semiconducting properties of the nanocarbons, and the possibility to have the band gap within the visible-light region through defect band engineering, introduction of light heteroatoms and control O groups) enhancing charge separation by trapping electrons. These nanocarbons open a range of new possibilities for photocatalysis both for energetic and environmental applications. The use of nanocarbons as quantum dots and photoluminescent materials was also analysed

Photoactive materials based on semiconducting nanocarbons-A challenge opening new possibilities for photocatalysis

This perspective paper introduces the concept that nanocarbons and related materials such as carbon dots are an interesting intrinsic photocatalytic semiconducting material, and not only a modifier of the existing (semiconducting) materials to prepare hybrid materials. The semiconducting properties of the nanocarbons, and the possibility to have the band gap within the visible-light region through defect band engineering, introduction of light heteroatoms and control O groups) enhancing charge separation by trapping electrons. These nanocarbons open a range of new possibilities for photocatalysis both for energetic and environmental applications. The use of nanocarbons as quantum dots and photoluminescent materials was also analysed

H2 production by selective photo-dehydrogenation of ethanol in gas and liquid phase on CuOx/TiO2 nanocomposites

CuOx/TiO2 nanocomposites prepared by copper photodeposition (1.0 and 2.5 wt% copper loading) on TiO2 (synthesized by three different routes) are studied in the ethanol photo-dehydrogenation in gas- and liquid-phase operations, and characterized in terms of surface area, phase composition by XRD, morphology and copper-oxide nanoparticle size distribution, and copper species by UV-visible diffuse reflectance spectroscopy. Cu2+ ions partially enter into the titania structure leading to the creation of oxygen vacancies responsible for the shift in the band gap, but also the creation of traps for photogenerated holes and electrons. While the band gap shifts to lower energies with the copper content, a maximum photocatalytic activity is shown for the intermediate copper loading. Gas-phase operations allow a higher H2 productivity with respect to liquid-phase operations, and especially a higher selectivity (about 92\u201393%) to acetaldehyde. It is remarked that the route of photo-dehydrogenation of ethanol to H2 and acetaldehyde has an economic value about 3.0\u20133.5 times higher than the alternative route of photoreforming to produce H2. Gas-phase operations would be preferable for the photo-dehydrogenation of ethanol