Influence of zeolitic structure on photoreduction property and hydrogen evolution reaction

A new photocatalytic material developed by supporting TiO2 in combination with transition metal ion like cobalt and heteropolyacid (HPA) on the surface is facilitating enhanced photoreduction of water and methyl orange. Zeolites being a solid acid play an important role in the electron transfer reaction, facilitated by the Lewis acid sites in the form of aluminium ions. In the present work, four different zeolite matrices namely, NaY zeolite, ultrastable zeolite Y, beta zeolite and titanium silicate-1 have been used for the synthesis of new photocatalytic materials. These materials have been evaluated for water splitting by an initial screening procedure using methyl orange photoreduction. The photocatalyst containing Na Y has emerged as a potential photocatalyst with hydrogen evolution rate of 2730 mmol/h/g of TiO2. Hydrogen evolution was not observed for the composite photocatalysts synthesized using the other zeolite matrices. It has been observed that physicochemical properties like Si/Al ratio, acidity and basicity of the zeolite support have a tremendous influence on the photoreduction property of these zeolite matrices

Efficient photocatalytic hydrogen generation by silica supported and platinum promoted titanium dioxide

Titanium dioxide was supported on mesoporous silica and promoted with Pt and Ru. The supported photocatalysts show high surface area and better photocatalytic activity in visible light as compared to the benchmark Degussa P25. These photocatalysts were characterized using XRD, BET-SA, and UV-DRS techniques. The surface area of supported photocatalyst was 140.6 m2/g which is higher than Degussa P- 25. Supported photocatalyst was evaluated for hydrogen evolution via water splitting reaction using ethanol as a sacrificial donor. Hydrogen yield observed is 4791.43 mmol/h/g of TiO2 and that for P-25 is 161 mmol/h/g of TiO2 under visible light irradiation. The value is 30 times higher than benchmark material Degussa P-25. This photocatalyst is also found stable up to 24 h without replenishing with sacrificial donor ethanol. However silica gel/TiO2/Ru does not show any exciting result for hydrogen generation. The effect of various operating parameters like photocatalyst loading, Illumination time and intensity of light on supported photocatalyst also has been studied

Chlorophyll-based photocatalysts and their evaluations for methyl orange photoreduction

Immobilization of chlorophyll on different functionalized mesoporous materials has been attempted. The replacement of butanediol with monoethanol amine has resulted in increase in chlorophyll loading by a factor of two. The maximum immobilization of chlorophyll was on MCM-41 functionalized with monoethanolamine MCM-41/MEA/Chl) as compared to other mesoporous materials. This material has been characterized using XRD, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy (SEM-EDX) and fluorescence spectroscopy. The photocatalytic reduction ofmethyl orange (MO)was studied using MCM-41/MEA/Chl as photocatalyst under the visible light. The photocatalytic reduction of MO was 0.396 mg/g of MCM-41/MEA/Chl photocatalyst as compared to 0.508 mg/g of TiO2 for that of Degussa P-25 photocatalyst. The effect of various operating parameters like catalyst loading, initial concentration and intensity of light has also been studied. Photocatalytic property of chlorophyll-based photocatalytic material indicates that chlorophyll acts as a reaction center, which absorbs visible light and generates electron, which is transferred to different electron acceptors reducing MO into derivative of hydrazine

Hydrogen evolution by a low cost photocatalyst: Bauxite residue

Bauxite residue or red mud which is an aluminium industry waste has been used as a novel low cost photocatalyst active in visible light for the generation of hydrogen from water. The driving force behind the use of bauxite residue as a photocatalyst is not only the fact that it is widely available but also bauxite residue is a fine grained mixture of oxides and hydroxides (Fe2O3, TiO2, SiO2, and Al2O3, Al(OH)3). The photocatalyst was characterized with respect to BET-SA, UV-DRS, XRD, SEM and EDX. Hydrogen yield of 4600 mmol/h/g of TiO2 was achieved as compared to hydrogen evolution rate of 164 mmol/h/g of TiO2 for commercially available titania Degussa P-25. However, the hydrogen evolution was 20.85 mmol/h/g of photocatalyst. The results suggest that bauxite residue appears to be a novel low cost photocatalyst. The various operating conditions of photocatalytic hydrogen generation were studied which include amount of catalyst, illumination intensity, illumination time, effect of various sacrificial donors etc

Throwing light on platinized carbon nanostructured composites for hydrogen generation

In the present study, we have synthesised carbon nanoparticles (CNPs) through a relatively simple process using a hydrocarbon precursor. These synthesised CNPs in the form of elongated spherules and/or agglomerates of 30–55 nm were further used as a support to anchor platinum nanoparticles. The broad light absorption (300–700 nm) and a facile charge transfer property of CNPs in addition to the plasmonic property of Pt make these platinized carbon nanostructures (CNPs/Pt) a promising candidate in photocatalytic water splitting. The photocatalytic activity was evaluated using ethanol as the sacrificial donor. The photocatalyst has shown remarkable activity for hydrogen production under UV-visible light while retaining its stability for nearly 70 h. The broadband absorption of CNPs, along with the Surface Plasmon Resonance (SPR) effect of PtNPs singly and in composites has pronounced influence on the photocatalytic activity, which has not been explored earlier. The steady rate of hydrogen was observed to be 20 mmol h�1 with an exceptional cumulative hydrogen yield of 32.16 mmol h�1 g�1 observed for CNPs/Pt, which is significantly higher than that reported for carbon-based systems

Throwing light on platinized carbon nanostructured composites for hydrogen generation

In the present study, we have synthesised carbon nanoparticles (CNPs) through a relatively simple process using a hydrocarbon precursor. These synthesised CNPs in the form of elongated spherules and/or agglomerates of 30-55 nm were further used as a support to anchor platinum nanoparticles. The broad light absorption (300-700 nm) and a facile charge transfer property of CNPs in addition to the plasmonic property of Pt make these platinized carbon nanostructures (CNPs/Pt) a promising candidate in photocatalytic water splitting. The photocatalytic activity was evaluated using ethanol as the sacrificial donor. The photocatalyst has shown remarkable activity for hydrogen production under UV-visible light while retaining its stability for nearly 70 h. The broadband absorption of CNPs, along with the Surface Plasmon Resonance (SPR) effect of PtNPs singly and in composites has pronounced influence on the photocatalytic activity, which has not been explored earlier. The steady rate of hydrogen was observed to be 20 mu mol h(-1) with an exceptional cumulative hydrogen yield of 32.16 mmol h(-1) g(-1) observed for CNPs/Pt, which is significantly higher than that reported for carbon-based systems

Photocatalytic hydrogen generation through water splitting on nano-crystalline LaFeO3 perovskite

Visible light active ABO3 type photocatalyst with LaFeO3 composition was synthesized by sol-gel method. The photocatalyst was characterized by different techniques such as X-ray diffraction, BET surface area analysis, particle size analysis, scanning electron microscopy, UVevisible diffuse reflectance spectroscopy (UVeVisible DRS), and photoluminescence spectroscopy. LaFeO3 photocatalyst exhibited an optical band gap of 2.07 eV with the absorption spectrum predominantly in visible region of the spectrum. The BET surface area of photocatalyst LaFeO3 was observed as 9.5 m2/g, with the crystallite size of 38.8 nm as calculated by the Debye-Scherer equation. The photocatalytic activity of LaFeO3 was investigated for hydrogen generation through sacrificial donor assisted photocatalytic water splitting reaction by varying conditions in feasible parametric changes using visible light source, ethanol as a sacrificial donor and Pt solution of H2PtCl6 as a co-catalyst. The rate of photocatalytic hydrogen evolution was observed to be 3315 mmol g�1 h�1 under optimized conditions and using 1 mg dose of photocatalyst with reaction time of 4 h and illumination of 400 W

Visible light induced photoreduction of water by N-doped mesoporous titania

N-doped mesoporous titania was synthesized by templating method. Three different types of photocatalysts were synthesized by varying chitosan to titania compositions and designated as N-doped mesoporous titania (1:1), (1:2) and (1:3). These synthesized photocatalysts were characterized by XRD, BET-SA, UV-DRS, SEM-EDX and XPS. This photocatalyst is active in visible range with band gap energy of 2.65 eV. Formation of TieN bond reveals the decrease in the band gap of TiO2. The synthesized photocatalysts were screened initially for their photocatalytic activity using water splitting reaction. The maximum hydrogen yield of 2654.57 mmol/h/g of photocatalyst was obtained for N-doped mesoporous titania (1:2). This yield is 16 times higher as compared to the bench mark material Degussa P-25 (161 mmol/h/g of photocatalyst). The best performing photocatalyst N-doped mesoporous titania (1:2) was investigated in detail to study the influence of various operating parameters. Reuse and recycle study results in steady hydrogen yield of 9605.56 mmoles for 30 h