A flame synthesis method has been used to prepare nanosized, high-surface-area Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts from aqueous solutions of metal acetate precursors. The particles were formed by vaporization of the precursors followed by reaction and then gas to particle conversion. The specific surface areas of the synthesized powders ranged from 127 to 163 m(2)/g. High-resolution transmission electron microscope imaging showed that the particle diameters for the ceria materials are in the range of 3-10 nm, and a thin layer of amorphous material was observed on the surface of the particles. The presence and surface enrichment of the transition-metal oxides (CuO, NiO, and Fe(2)O(3)) on the ceria particles were detected using X-ray photoelectron spectroscopy. Electron energy-loss spectroscopic studies suggest the formation of a core-shell structure in the as-prepared particles. Extended X-ray absorption fine structure studies suggest that the dopants in all M-Ce-O systems are almost isostructural with their oxide counterparts, indicating the doping materials form separate oxide phases (CuO, Fe(2)O(3), NiO) within the host matrix (CeO(2)). Etching results confirm that most of the transition-metal oxides are present on the surface of CeO(2), easily dissolved by nitric acid. The performance of the flame-synthesized catalysts was examined toward water-gas shift (WGS) activity for fuel processing applications. The WGS activity of metal ceria catalysts decreases in the order Cu-Ce-O > Ni-Ce-O > Fe-Ce-O > CeO(2) with a feed mixture having a hydrogen to carbon monoxide (H(2)/CO) ratio of 1. There was no methane formation for these catalysts under the tested conditions.

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Tenorite CuO thin films have been synthesized via spray pyrolysis of aqueous copper(II) chloride solution followed by heat-treatment, exhibited a photocurrent density of 24 mA cm −2 at 0.25 V vs. RHE under AM 1.5G solar irradiation in alkaline electrolyte. This large photocurrent density has been attributed to a drift assisted transport of photo-generated electrons across the semiconductor/electrolyte interface in the annealed films. The tendency of photo-corrosion from the surface of CuO has been reduced substantially without any extra protective layer, simply by adding K 3 Fe(CN) 6 in the electrolyte, which acts as a sacrificial excess-electron scavenging agent. The fabricated electrode exhibited a positive onset potential at 0.25 V vs. RHE even after the electrolyte modification and a stable photocurrent density of more than 40% has been retained after 20 minutes of continuous illumination. The processed photocathode showed a solar to chemical conversion efficiency of 7.85% and 21.5% with and without using an electron scavenging agent, respectively. It holds the promise of using this photocathode in PEC energy conversion, photocatalysis and solar water splitting.In the exploration of terrestrially employable carbon-free energy sources, materials play a central role in the generation and storage of electrical as well as chemical energies. 1,2 Semiconducting materials are especially important to harvest the solar energy due to their bandgap energies matching to that of the visible photons. Photovoltaic (PV) and photoelectrochemical (PEC) methods are the two solar energy conversion modes those utilize semiconductor materials. In order to apply semiconductors in PEC applications, three important aspects must be satisfied: first, capability of providing large photocurrent density; second, a long term stability; and third, the scalability. 3 Several semiconductors, such as have been explored in the PEC applications with majority as catalysts for water splitting. The hunt for novel structure and materials design thus continues to set off the above requirements. Oxides of copper (CuO and Cu 2 O) have recently drawn special attention due to their relative abundance on the earth crust. Majority of the recently reported investigations are focused on Cu 2 O. [25][26][27][28][29][30][31][32] Due to the chemical instability and poor electron transfer, its nano-composites with other oxides or metal catalysts have been attempted. [33][34][35] On the other hand, CuO is chemically more stable than Cu 2 O but there are only few studies on the PEC response of CuO have been reported so far. 36 Among various oxides of copper (viz. Cu 2 O, CuO and Cu 4 O 3 ), tenorite CuO is a chemically stable p-type semiconductors having an indirect bandgap in the range of 1.3-1.7 eV. 37-42 This property makes CuO a promising candidate for solar to chemical energy conversion with maximum possible theoretical photocurrent density in the range of 22-35 mAcm −2 under standard AM 1.5G solar irradiance corresponding to its high and low bandgap values, ...

Synthesis of cerium oxide nanocrystallites via precipitation using triethanolamine is reported. The molecular water associated with the cerium nitrate precursor is exploited to generate hydroxyl ions with the help of triethanolamine, facilitating precipitation. The small crystallite diameter (3 nm) in the as prepared powder is believed to result from the limited amount of water present. Solvent type has no effect on the final crystallite size or structure; however, it plays an important role in the dispersion of the nanoparticles with dispersity of the particles increasing with increasing carbon chain length of the solvent alcohol used.

Nanocrystalline ␣-Al 2 O 3 powders have been prepared by pyrolysis of a complex compound of aluminum with triethanolamine (TEA). The soluble metal-ion-TEA complex forms the precursor material on complete dehydration of the complex of aluminum-TEA. The single-phase ␣-Al 2 O 3 powder has resulted after heat treatment at 1025°C. The precursors and the heat-treated final powders have been characterized by X-ray diffractometry, thermogravimetric and differential thermal analysis, and transmission electron microscopy (TEM). The average particle sizes as measured from X-ray line broadening and TEM are ϳ25 nm. The powder has crystallite sizes of the same order indicates the poor agglomeration of crystallites.

Nanocrystalline MgAl 2 O 4 spinel powder was synthesized by pyrolysis of complex compounds of aluminum and magnesium with triethanolamine (TEA). The soluble metal ion-TEA complexes formed the precursor material on complete dehydration of the complexes of aluminum-TEA and magnesium-TEA. Single-phase MgAl 2 O 4 spinel powder resulted after heat treatment of the precursor material at 675°C. The precursor and the heat-treated powders were characterized by X-ray diffractometry (XRD), differential thermal and thermogravimetric analysis, and transmission electron microscopy (TEM). The average crystallite size as measured from the X-ray line broadening was around 14 nm and the average particle size from TEM studies was around 20 nm.

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