National Chemical Laboratory

About: National Chemical Laboratory is a facility organization based out in Pune, Maharashtra, India. It is known for research contribution in the topics: Catalysis & Enantioselective synthesis. The organization has 8891 authors who have published 14837 publications receiving 387600 citations.

A scalable and thin film approach for solar hydrogen generation: a review on enhanced photocatalytic water splitting

Abstract: Although nearly five decades of efforts have gone into solar water splitting (SWS), still success eludes and there is no big breakthrough till date. While huge importance is given either individually or concurrently to the three fundamental steps, namely, light absorption, charge carrier separation and diffusion and charge utilization at redox sites, many aspects that are practically helpful to improve the efficiency are not widely discussed and practised. Nonetheless, by adopting a number of small, but significant changes, solar hydrogen production can be enhanced. The present review discusses such different approaches employed for photocatalytic water splitting reported in the literature. For example, an increase of up to two orders of magnitude in solar hydrogen generation was observed with a film form compared to the particulate form of the same catalyst. Discussion on various approaches of enhanced hydrogen production under sunlight and one sun conditions is the main focus of this review, in particular with thin-film forms. The merits and demerits of thin film and particulate methods, respectively, are addressed in detail. Potential methods and successful stories on scalability are also discussed in the present review. In contrast to charge collection over a long distance in solar cell-based methods, a film-based method discussed shows that the local charge utilisation at a zero applied potential is an attractive feature for SWS. A comparison is provided between the PEC-WS and SWS for solar hydrogen generation, and how far we are from the reality to produce solar hydrogen on an industrial scale. We believe the presently practised diverse evaluation efforts may be truncated to fewer methods such as film-based evaluation and in a focussed manner to tackle the SWS issue towards sustainable production of solar hydrogen.

Epoxidation of styrene by anhydrous t-butyl hydroperoxide over gold supported on Al2O3, Ga2O3, In2O3 and Tl2O3

Abstract: Group IIIa metal (viz. Al, Ga, In and Tl) oxide-supported gold nanoparticles, prepared by deposition–precipitation (DP) using NaOH and by homogeneous deposition–precipitation (HDP) using urea, were employed as highly active/selective and reusable catalysts for the epoxidation of styrene (at 82 °C) by anhydrous t -butyl hydroperoxide (TBHP). The loading and average particle size of gold, when it was deposited on the Gr. IIIa metal oxides by the HDP, was found to increase in the following order: Al 2 O 3 (6.36 wt.%, 4.1 ± 2.3 nm) 2 O 3 (6.43 wt.%, 6.67 ± 3.7 nm) 2 O 3 (6.81 wt.%, 15.6 ± 6.3 nm) 2 O 3 (8.00 wt.%, 24.4 ± 13.1 nm). Both the activity and the epoxide selectivity of the supported gold catalysts are in the following order: Au/Al 2 O 3 2 O 3 2 O 3 2 O 3 . Using the DP method, the Au loading on Al 2 O 3 and Tl 2 O 3 was found to be 2.10 and 5.42 wt.%, respectively, such values are much lower than those achieved by the HDP method. The Al 2 O 3 , Ga 2 O 3 and In 2 O 3 supports alone showed little or no epoxidation activity/selectivity. However, the Tl 2 O 3 support alone showed the activity and epoxide selectivity comparable to that of the Au/Tl 2 O 3 catalysts. The surface species on the Au/Al 2 O 3 were found to be only metallic gold (Au 0 ) ones and Al in single oxidation state (Al 3+ ). However, the surface species on the Au/In 2 O 3 were both the metallic and ionic gold (Au 0 and Au 3+ ) and the indium in two oxidation states (In 3+ and In 2+ or In 1+ ). The gold loading and both the epoxidation activity and selectivity are increased with increasing the basicity and/or reduction potential of the support used in the supported Au catalysts.

A combined experimental and theoretical study of the structural, electronic and vibrational properties of bulk and few-layer Td-WTe2

Abstract: The recent discovery of non-saturating giant positive magnetoresistance has aroused much interest in Td-WTe2. We have investigated structural, electronic and vibrational properties of bulk and few-layer Td-WTe2 experimentally and theoretically. Spin–orbit coupling is found to govern the semi-metallic character of Td-WTe2 and its structural link with the metallic 1 T form provides an understanding of its structural stability. There is a metal-to-insulator switch-over in the electrical conductivity and a change in the sign of the Seebeck coefficient around 373 K. Lattice vibrations of Td-WTe2 have been analyzed using first-principles calculations. Out of the 33 possible zone-center Raman active modes, five distinct Raman bands are observed around 112, 118, 134, 165 and 212 cm−1 in bulk Td-WTe2. Based on symmetry analysis and calculated Raman tensors, we assign the intense bands at 165 cm−1 and 212 cm−1 to the and modes, respectively. Most of the Raman bands stiffen with decreasing thickness, and the ratio of the integrated intensities of the to bands decreases in the few-layer sample, while all the bands soften in both the bulk and few-layer samples with increasing temperature.

Crystalline Phases in Nylon-11: Studies Using HTWAXS and HTFTIR

Abstract: Nylon-11 was crystallized into different crystalline phases by appropriate methods. The change in the structure during heating was monitored in situ by wide-angle X-ray scattering (WAXS). The α phase obtained by precipitating nylon-11 in 1,4-butanediol started transforming into the pseudohexagonal phase on heating, but the transformation was not fully completed before melting. The melt crystallized sample at 175 °C gave the pseudohexagonal phase, which transformed into the α‘ phase on cooling to room temperature at about 100 °C. The d spacing of the 001 reflection also showed a change at the transition temperature. The melt-quenched sample showed the pseudohexagonal phase, which did not change during heating, but on cooling transformed into α‘ phase. The γ phase was obtained by casting nylon-11 in trifluoroacetic acid (TFA), and it changed into the pseudohexagonal phase at about 110 °C on heating. The d spacing of the 001 reflection depended on the way in which it was obtained. The studies have shown that...