D. Praveen Kumar

Synergistic effect of nanocavities in anatase TiO2 nanobelts for photocatalytic degradation of methyl orange dye in aqueous solution.

Nanocavities are empty voids exposed on the surface of one dimensional TiO2 nanostructured material. Often, they exhibited beneficial optical and electrical properties that leads to efficient photocatalytic reactions. This study reports formation of nanocavities on anatase TiO2 nanobelts (TNB) through dehydroxylation of surface hydroxyl groups during calcination process (350-600°C). The morphological and crystal structure analysis of TNB-500, -550 and -600 displayed the nanobelts shape with high density of nano-size cavities and increase in average diameter with calcination temperature. The SAED patterns confirm the anatase TiO2 phase. The enhanced light absorption properties of biphasic anatase/TiO2-B and anatase TiO2 than H2Ti3O7 are attributed to transformation of crystal structure upon calcination process. The catalytic activity was evaluated for degradation of methyl orange dye in aqueous solution under solar light irradiation. The reaction variables such as calcination temperature, amount of catalyst and pH of the methyl orange dye solution were studied and discussed in detail. Under optimal experimental conditions TNB-550 photocatalyst displayed highest degradation performance about 8 folds higher than H2Ti3O7. The high performance is explained as due to synergistic properties of one dimensional anatase TiO2 with high density of nanocavities leading to one dimensional transfer of electrons and high absorption co-efficient in UV-A spectrum are suitable for efficient red-ox reactions.

Benefits of tubular morphologies on electron transfer properties in CNT/TiNT nanohybrid photocatalyst for enhanced H2 production

In order to study the influence of one dimensional tubular structures for effective electron and hole transportation onto the surface of a photocatalyst leading to efficient solar photocatalytic hydrogen production, functionalized carbon nanotube (FCNT)/TiO2 nanotube nanohybrids were prepared. TiO2 nanotubes (TiNTs) were prepared by hydrothermal method. A series of novel functionalized carbon nanotube/TiO2 nanotube nanohybrids (CTT) were prepared for different wt% (1–20) of FCNTs by wet impregnation method to extend absorption in the visible region and also to retard the electron–hole pair recombination and thereby to enhance the H2 production capability under solar light irradiation. The functionalized carbon nanotube/TiO2 nanotube nanohybrids (CTT) were characterized with XRD, TEM, DRS-UV-Vis, Raman spectroscopy and XPS for crystal structure, morphology, optical properties and chemical composition. Addition of FCNTs to the TiNTs in CTT nanohybrids extended the absorption to the visible region. Relative electron–hole recombination times were measured with photoluminescence spectra. The highest H2 generation of 29 904 μmol g−1 was observed after 4 h under optimal conditions due to better separation of electron–hole pairs and electron conducting properties.

Co-catalyst free Titanate Nanorods for improved Hydrogen production under solar light irradiation

AbstractHarnessing solar energy for water splitting into hydrogen (H2) and oxygen (O2) gases in the presence of semiconductor catalyst is one of the most promising and cleaner methods of chemical fuel (H2) production. Herein, we report a simplified method for the preparation of photo-active titanate nanorods catalyst and explore the key role of calcination temperature and time period in improving catalytic properties. Both as-synthesized and calcined material showed rod-like shape and trititanate structure as evidenced from crystal structure and morphology analysis. Notably, calcination process affected both length and diameter of the nanorods into shorter and smaller size respectively. In turn, they significantly influenced the band gap reduction, resulting in visible light absorption at optimized calcination conditions. The calcined nanorods showed shift in optical absorption band edge towards longer wave length than pristine nanorods. The rate of hydrogen generation using different photocatalysts was measured by suspending trititanate nanorods (in the absence of co-catalyst) in glycerol-water mixture under solar light irradiation. Among the catalysts, nanorods calcined at 250∘C for 2 hours recorded high rate of H2 production and stability confirmed for five cycles. Photocatalytic properties and plausible pathway responsible for improved H2 production are discussed in detail. Graphical AbstractOne dimensional rod-shaped titanate catalyst effectively delocalized the photogenerated charge carriers (electron-hole) along its length but confined its movement to exterior walls of nanorods. Unique properties of the catalyst triggered high rate of hydrogen evolution from glycerol-water mixture in the absence of noble metal or metal oxide co-catalyst under solar light irradiation.

Solar light active CuO/TiO 2 nanobelt photocatalyst for enhanced H 2 production

The best strategy for clean H₂ production is development of efficient photocatalyst systems for water splitting into H₂ and O₂ gases. Copper oxide deposited on 1-D TiO₂ nanobelts (TB) tested for photocatalytic water splitting in the presence of glycerol as scavenger under natural solar light irradiation. The influence of amount of Cu-loading and effect of calcination temperature on rate of H₂ production is revealed. The preliminary results evidenced that enhanced photocatalytic activity of CuO/TB (CTB) and showed 5 folds higher amount of H₂ production than TiO₂ nanoparticles. This high activity is attributed to synergic function of TiO₂ nanobelts and CuO as well.