Chemical hydrides:Asolution to high capacity hydrogen storage and supply

Cycloalkanes are good candidate media for hydrogen storage (6.5 wt% and 60.62 kgH2/m3). A novel approach for the supply of hydrogen, through liquid organic hydrides (LOH) using catalytic reaction pair of dehydrogenation of cycloalkanes and hydrogenation of corresponding aromatics is a useful process for supply of hydrogen. Hydrogenation of aromatics is relatively well-established process. However, the efforts are needed to develop efficient catalyst for dehydrogenation of cycloalkanes. In this paper we review the dehydrogenation of cycloalkanes as useful reaction for storage of hydrogen in chemical hydride

Au-TiO2 nanocomposites and efficient photocatalytic hydrogen production under UV-visible and visible light illuminations: a comparison of different crystalline forms of TiO2

Au[subscript (~1 wt%)]/TiO[subscript 2(anatase or rutile or P25)] nanocomposites were prepared by the solvated metal atom dispersion (SMAD) method, and the as-prepared samples were characterized by diffuse reflectance UV-visible spectroscopy, powder XRD, BET surface analysis measurements, and transmission electron microscopy bright field imaging. The particle size of the embedded Au nanoparticles ranged from 1 to 10 nm. These Au/TiO[subscript 2] nanocomposites were used for photocatalytic hydrogen production in the presence of a sacrificial electron donor like ethanol or methanol under UV-visible and visible light illumination. These nanocomposites showed very good photocatalytic activity toward hydrogen production under UV-visible conditions, whereas under visible light illumination, there was considerably less hydrogen produced. Au/P25 gave a hydrogen evolution rate of 1600 mol/h in the presence of ethanol (5 volume %) under UV-visible illumination. In the case of Au/TiO[subscript 2] prepared by the SMADmethod, the presence of Au nanoparticles serves two purposes: as an electron sink gathering electrons from the conduction band (CB) of TiO[subscript 2] and as a reactive site for water/ethanol reduction to generate hydrogen gas. We also observed hydrogen production by water splitting in the absence of a sacrificial electron donor using Au/TiO[subscript 2] nanocomposites under UV-visible illumination

Visible light active zeolite-based photocatalysts for hydrogen evolution from water

Hydrogen, considered as the fuel for future can be produced from non-conventional, renewable and plentiful source like water. Novel zeolite-based materials that show photocatalytic properties in the visible light have been synthesized by incorporating titanium dioxide (TiO2), heteropolyacid (HPA) and transition metals like cobalt (Co). These materials show high efficiency for water splitting under visible light irradiation. Hydrogen (H2) generation to the tune of 2730 mmol/h/g TiO2 has been obtained for the composite photocatalyst synthesized. Platinum (Pt) doping has also been attempted in this composite photocatalyst, however, no substantial enhancement in hydrogen generation was observed. The high efficiency of the composite photocatalyst suggests that the TiO2 which gets effectively dispersed and stabilized on the surface of zeolite works synergistically with transition metal like cobalt and heteropolyacid to make the material active in visible light for photoreduction of water to hydrogen. The aluminosilicate framework of zeolite also contributes towards delayed charge separation. This composite photocatalyst shows improvement in hydrogen evolution rate over other TiO2 based visibly active photocatalyst reported

PHOTOCATALYTIC HYDROGEN GENERATION BY ETHANOL ASSISTED WATER SPLITTING REACTION USING MIXED OXIDE OF Ba AND Mn

Visible light active BaMnOx type photocatalyst was synthesized by using sol-gel method. The photocatalyst was characterized by X- ray diffraction, BET-SA, and UV-visible diffused reflectance spectroscopy (UV-DRS). BaMnOx photocatalyst exhibited an optical band gap of 2.9 eV with the absorption predominantly in visible region of the light spectrum. The crystallite size of BaMnOx is 24.63 nm as calculated by the Debye Scherer equation. The BET surface area value for BaMnOx photocatalyst was found to be 16.2 m2/g. The photocatalytic hydrogen generation was carried out by using Pt as co-catalyst and ethanol as a sacrificial donor. Hydrogen generation was investigated by ethanol assisted water splitting reaction under visible light irradiation, using a compact glass reactor and tungsten lamp as a source of visible light. The rate of photocatalytic hydrogen evolution was observed to be 7463 μmol.g-1.h-1 of Pt-BaMnOx photocatalyst

Defluoridation of drinking water using chemically modified bentonite clay

Adsorption potential of metal oxide (lanthanum, magnesium and manganese) incorporated bentonite clay was investigated for defluoridation of drinking water using batch equilibrium experiments to gain insight of adsorption behavior, kinetics and mechanisms of adsorption of fluoride ion. The effect of various physicochemical parameters such as pH, adsorbent dose, initial fluoride concentration and the presence of interfering co-ions on adsorption of fluoride has been investigated. The 10%La-bentonite shows higher fluoride uptake capacity for defluoridation of drinking water as compared to Mg-bentonite, Mn-bentonite and bare bentonite clay. The uptake of fluoride in acidic pH was higher as compared to alkaline pH. The equilibrium adsorption data fitted reasonably well in both Langmuir and Freundlich isotherm models. It was also observed that in the presence of certain co-existing ions can have positive effect on removal of fluoride, while carbonate and bicarbonate anions show deleterious effect. The rate of adsorption was reasonably rapid and maximum fluoride uptake was attained within 30 min. The modified adsorbent material shows better fluoride removal properties for actual field water, which could be due to the positive effect of other co-ions present in the field water

Transition metals supported on mesoporous ZrO2 for the catalytic control of indoor CO and PM emissions

Mesoporous ZrO2 support has been prepared by using a low cost natural biopolymer chitosan as template, and different transition metals from the first row (Fe, Co, Ni, Cu and Mn) were impregnated on the synthesized support. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, TEM, O2-TPD and TG analysis to study the material details as well as to understand the catalytic mechanism. The activity of these catalysts has been investigated for CO and PM oxidation. Incorporation of transition metals improved the activity for both CO and PM oxidation. It has been observed that Co–ZrO2 is the most active catalyst for studied reactions while, Ni based catalysts show the lowest activity for both the reactions. The transition metal supported catalysts follow the activity sequence Co–ZrO2 > Mn–ZrO2 > Cu–ZrO2 > Fe–ZrO2 > Ni–ZrO2. The effect of CO2, SO2 and H2O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. The characterization of the materials by O2-TPD studies explains the better catalytic performance for the Co–ZrO2, Mn–ZrO2 and Cu–ZrO2 catalysts, as compared to Fe–ZrO2 and Ni–ZrO2. Such mesoporous zirconia with reasonably good surface area and without ordered structure could be useful for both CO and PM oxidation reactions

Plasmonics driven engineered pasteurizers for solar water disinfection (SWADIS)

Rampant environmental pollution is the most ubiquitous concern of current world. A sustainable panacea to overarching contamination of water-borne pathogens demands cheap and eco-friendly oriented research. Solar energy is effortlessly accessible in most of the weather conditions and can be used for water decontamination. In this context, Solar Water Disinfection (SWADIS) appears to be feasible solution. Herein we are reporting newly developed Carbon nanoparticles (CNP) which shows absorption of light in broad region extending from Ultraviolet–Visible (UV) to Infrared Spectroscopy (IR). This CNP with pronounced photothermal effect has been used for SWADIS. Photothermal effect of plasmonic nanomaterials has massive potential and has exploited for disinfection of water. Moving towards practical device design we have developed an efficient CNP based Multipurpose Solar Pasteurizer (MSP) and Nano-Solar Pasteurizer (NSP) which can efficiently perform the SWADIS. Result shows that upon irradiation under natural solar radiation pasteurizers can thermally inactivate the bacteria. The system proves to be able to perform 100% bacterial inactivation in sunny days. We also conducted bacterial inactivation experiments by simulating 106 CFU mL−1 concentration of E. coli in water to mimic field conditions. Results are evident that pasteurizers achieved 100% bacterial inactivation within period of ˜45 min under sunlight

Nano-ferrites for water splitting: unprecedented high photocatalytic hydrogen production under visible light

In the present investigation, hydrogen production via water splitting by nano-ferrites was studied using ethanol as the sacrificial donor and Pt as co-catalyst. Nano-ferrite is emerging as a promising photocatalyst with a hydrogen evolution rate of 8.275 mmol h�1 and a hydrogen yield of 8275 mmol h�1 g�1 under visible light compared to 0.0046 mmol h�1 for commercial iron oxide (tested under similar experimental conditions). Nano-ferrites were tested in three different photoreactor configurations. The rate of hydrogen evolution by nano-ferrite was significantly influenced by the photoreactor configuration. Altering the reactor configuration led to sevenfold (59.55 mmol h�1) increase in the hydrogen evolution rate. Nano-ferrites have shown remarkable stability in hydrogen production up to 30 h and the cumulative hydrogen evolution rate was observed to be 98.79 mmol h�1. The hydrogen yield was seen to be influenced by several factors like photocatalyst dose, illumination intensity, irradiation time, sacrificial donor and presence of co-catalyst. These were then investigated in detail. It was evident from the experimental data that nano-ferrites under optimized reaction conditions and photoreactor configuration could lead to remarkable hydrogen evolution activity under visible light. Temperature had a significant role in enhancing the hydrogen yield

La0.9Ba0.1CoO3 perovskite type catalysts for the control of CO and PM emissions

Perovskite type catalysts with LaCoO3 and La0.9Ba0.1CoO3 compositions have been prepared by sol–gel method and their catalytic activity was studied for CO oxidation in presence of CO2, water and also for particulate matter (PM)/carbon oxidation. The catalysts were characterized using XRD, BET-SA, SEM, TPD, XPS and their catalytic activity was evaluated using a steady state gas evaluation assembly, as well as thermo gravimetric analysis. La0.8Ba0.1CoO3 catalyst shows enhanced catalytic activity as compared to LaCoO3 for CO and PM oxidation. Barium substitution appears to be responsible for low temperature activity of the catalyst by influencing redox and oxygen desorption properties as also suggested by TPD studies

Tyrosinase-Immobilized MCM-41 for the Detection of Phenol

In the present investigation, we report the immobilization of the enzyme tyrosinase on mesoporous silica material, i.e. MCM-41 to serve as a tool for the detection of phenol. The enzyme immobilized onto the MCM-41 matrix has shown to retain its activity and is quite stable. The immobilization of enzyme has been discussed, and the various factors that affect the loading of enzyme onto MCM-41 were studied and optimized. The applicability of tyrosinase-immobilized MCM-41 was then demonstrated for the detection of phenol. The lowest detectable concentration of phenol by tyrosinaseimmobilized MCM-41 was observed to be 1 mg l−1. The factors influencing the detection of phenol were then studied in detail