Sadhana Rayalu

Removal of As(III) and As(V) from water by copper oxide incorporated mesoporous alumina

In the present manuscript a new adsorbent namely copper oxide incorporated mesoporous alumina (COIMA) for removal of arsenic from water is reported. The COIMA was prepared by treating mesoporous alumina with copper sulphate solution followed by calcination at 450°C in the presence of air. Various adsorption isotherm and kinetic parameters were computed using batch adsorption studies to determine the adsorption capacity for As(III) and As(V) and to understand the mechanism of adsorption. It was observed that incorporation of copper oxide improves the adsorption capacity of unmodified alumina from 0.92 to 2.16 mg g(-1) for As(III) and from 0.84 to 2.02 mg g(-1) for As(V). The results revealed that the adsorption follows Langmuir isotherm and pseudo-second-order kinetic models for both As(III) and As(V). The material is capable of simultaneously removing As(III) and As(V) with removal efficiencies of more than 95% for both As(III) and As(V). Assessment of the water quality before and after treatment with COIMA also confirmed that the there is no leaching of copper and other parameters were also within permissible limits of Indian drinking water standard indicating that the COIMA can be used for treatment of arsenic contaminated drinking water.

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

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 10u2009nm. These Au/TiO2 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 1600u2009μmol/h in the presence of ethanol (5 volume %) under UV-visible illumination. In the case of Au/TiO2 prepared by the SMAD method, the presence of Au nanoparticles serves two purposes: as an electron sink gathering electrons from the conduction band (CB) of TiO2 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/TiO2 nanocomposites under UV-visible illumination.

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 μmol 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.

Copper Oxide Nanograss for Efficient and Stable Photoelectrochemical Hydrogen Production by Water Splitting

A biphasic copper oxide thin film of grass-like appendage morphology is synthesized by two-step electro-deposition method and later investigated for photoelectrochemical (PEC) water splitting for hydrogen production. Further, the thin film was characterized by UV–Visible spectroscopy, x-ray diffraction (XRD), Scanning electron microscopy (SEM) and PEC techniques. The XRD analysis confirms formation of biphasic copper oxide phases, and SEM reveals high surface area grass appendage-like morphology. These grass appendage structures exhibit a high cathodic photocurrent of −xa01.44xa0mAcm−2 at an applied bias of −xa00.7 (versus Ag/AgCl) resulting in incident to photon current efficiency (IPCE) of ∼xa010% at 400xa0nm. The improved light harvesting and charge transport properties of grass appendage structured biphasic copper oxides makes it a potential candidate for PEC water splitting for hydrogen production.Graphical Abstract

Effect of Morphology of Platinum Nanoparticles on Benzene Oxidation Activity

The effect of morphology of Platinum (Pt) nanoparticles supported on alumina (γ-Al2O3) for complete catalytic oxidation of volatile organic compounds (VOCs) was investigated. Pt nanoparticles were synthesized through a simple method comprising of reduction followed by calcination of metal precursor coated chitosan templates using three different reducing agents: sodium borohydride (NaBH4), hydrazine (N2H4) and hydrogen (H2). The morphology and facet orientation of Pt nanoparticles were influenced by the reducing agents. The catalytic oxidation performance studies of these Pt nanoparticles loaded on γ-Al2O3 for VOCs showed strong dependence of their activities on their morphologies. High indexed facet (220) Pt nanosheets synthesized through NaBH4 reduction showed superior catalytic oxidation activity compared to the catalysts prepared using other reducing agents. Cyclic performance studies on these catalysts showed stable benzene oxidation performance implying their thermal stability. The absence of any shape directing agents in the synthesis of Pt nanoparticles with homogeneous morphologies and preferential orientation is an aspect that can be extended to other catalytic applications.