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

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

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

Photodeposition of AuNPs on metal oxides: Study of SPR effect and photocatalytic activity

Effect of photodeposition of AuNPs (gold nanoparticles) on TiO2, CeO2, Cu2O and Fe3O4 supports has been illustrated on sacrificial donor based hydrogen evolution. The synthesized samples were characterized by diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). Highest photocatalytic activity was exhibited by Au/TiO2 followed by Au/Fe3O4, Au/CeO2 and Au/Cu2O. Au/TiO2 under optimized conditions has shown significantly high photocatalytic activity under both UV–visible and visible radiation. Au/TiO2 shows hydrogen evolution rate of 920 μmol h−1 and 32.4 μmol h−1 under UV–visible and visible radiation, respectively. Significant enhancement in hydrogen evolution rate under visible light is very encouraging and may be attributed to polydispersed nature of AuNPs wherein larger particles facilitate light absorption and the smaller function as catalytic sites. Further studies are in progress to study the influence of various parameters on photocatalytic activity of Au/TiO2.ISSN: 0360-319

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

Photocatalytic Degradation of Phenolics by N-Doped Mesoporous Titania under Solar Radiation

In this study, nitrogen-doped mesoporous titania was synthesized by templatingmethod using chitosan. This biopolymer chitosan plays the dual role of acting as a template (which imparts mesoporosity) and precursor for nitrogen. BET-SA, XRD, UV-DRS, SEM, and FTIR were used to characterize the photocatalyst. The doping of nitrogen into TiO2 lattice and its state was substantiated and measured by XPS. The photocatalytic activity of the prepared N-doped mesoporous titania for phenol and o-chlorophenol degradation was investigated under solar and artificial radiation. The rate of photocatalytic degradation was observed to be higher for o-chlorophenol than that of phenol. The photodegradation of o-chlorophenol was 98.62% and 72.2%, while in case of phenol, degradation to the tune of 69.25% and 30.58% was achieved in solar and artificial radiation. The effect of various operating parameters, namely, catalyst loading, pH, initial concentration and the effect of coexisting ions on the rate of photocatalytic degradation were studied in detail

Nano cobalt oxides for photocatalytic hydrogen production

Nano structured metal oxides including TiO2, Co3O4 and Fe3O4 have been synthesized and evaluated for their photocatalytic activity for hydrogen generation. The photocatalytic activity of nano cobalt oxide was then compared with two other nano structured metal oxides namely TiO2 and Fe3O4. The synthesized nano cobalt oxide was characterized thoroughly with respect to EDX and TEM. The yield of hydrogen was observed to be 900, 2000 and 8275 mmol h�1 g�1 of photocatalyst for TiO2, Co3O4 and Fe3O4 respectively under visible light. It was observed that the hydrogen yield in case of nano cobalt oxide was more than twice to that of TiO2 and the hydrogen yield of nano Fe3O4 was nearly four times as compared to nano Co3O4. The influence of various operating parameters in hydrogen generation by nano cobalt oxide was then studied in detail

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

Visible light induced photoreduction of methyl orange by N-doped mesoporous titania

N-doped mesoporous titania was synthesized using templating method. Biopolymer chitosan was used as a template and also as a nitrogen source along with ammonium hydroxide. Three different types of Ndoped mesoporous titania were synthesized by varying composition of chitosan and titania precursor. These photocatalysts were characterized using XRD, BET-SA, FTIR, UV-DRS, SEM–EDX and XPS analysis. The photocatalytic activity of mesoporous titania was studied by methyl orange (MO) photoreduction reaction. From the experimental results it was observed that the N-doped mesoporous titania (1:2) gives the highest photocatalytic reduction of MO as compared to N-doped mesoporous titania prepared with (1:1) and (1:3) stoichiometry. This could be due to the optimal level of ‘N’ incorporation in the N-doped mesoporous titania (1:2). Photocatalysts reduce theMO dye into derivative of hydrazine. Photoactivity of N-doped mesoporous titania (1:2) is 1.0721 mg of MO reduced per g of TiO2 vis-a` -vis 0.508 mg of MO reduced per g of TiO2 for Degussa P25 photocatalyst. The effect of various operating parameters like photocatalyst loading, initial concentration and intensity of light also has been studied