X-ray photoelectron spectroscopic studies on Pd/CdS
01 Jan 1993-Journal of Materials Science Letters (Kluwer Academic Publishers)-Vol. 12, Iss: 19, pp 1536-1538
TL;DR: Ramakrishnan et al. as discussed by the authors used X-ray photoelectron spectroscopy (XPS) to probe the surface of materials and obtained a detailed surface study of Pd/CdS.
Abstract: I. B. RUFUS*,V. RAMAKRISHNAN, B. VISWANATHAN, J. C. KURIACOSE Department of Chemistry, Indian Institute of Technology, Madras 600036, India Metallized CdS is used as a photocatalyst for many reactions and as a photoanode in photoelectrochem- ical (PEC) cells [1-4]. Conversion and storage of solar energy can be achieved by means of photocata- lysis as well as by PEC cells. The photocatalytic and photoelectrochemical properties of metallized CdS depend on its surface properties. Pd/CdS is a better photocatalyst and photoanode than CdS [3]. However, a detailed surface study of Pd/CdS is lacking. X-ray photoelectron spectroscopy (XPS) is a versatile tool to probe the surface of materials. XPS investigation of Pd/CdS will yield useful infor- mation such as the oxidation state of Pd, the contact between Pd and CdS, and other species present on the surface. Metallized CdS is mostly prepared by the photodeposition of noble metals [1, 3, 4]. There- fore, in the present investigation Pd, one of the representatives of noble metals, was photodeposited on CdS and the Pd/CdS obtained was analysed by XPS. Pd, Pt, Rh, Ru and Ni/CdS were prepared by the simultaneous photodeposition (illuminating for 15 min with a 1000 W tungsten-halogen lamp) of these metals on a sintered (4 h at 873 K in nitrogen) CdS (Fluka, 99.999% purity) pellet from an equi- molar (1 x 10 -4 M) solution (acetic acid, pH 4.5) of the corresponding metal chlorides. Following a similar procedure, Pd was photodeposited from a solution of PdC12 (Arora Mathey Ltd, India). After photodeposition the pellets were washed with triply distilled water and dried in air at room temperature (303 K). The sides of the pellets that were exposed to visible light during the photodeposition were subjected to XPS analysis. The XPS studies were made with an ESCA Lab Mk II (VG Scientific Co., UK) at room temperature and at a pressure of 1 x 10 -7 Pa before and after sputtering with argon ions. The X-ray source used was MgKo~ with an energy of 1253.6 eV. The C ls peak at 285.0 eV was used as the internal standard. In the cases of Pd, Pt, Rh, Ru and Ni/CdS prepared by the simultaneous photodeposition of these metals, the Pd 3d and 3p binding energies (Figs 1 and 2) are higher than those reported for Pd metal, viz. 344.7, 340.0 and 531.5 eV [5], indicating that Pd which is on the surface of CdS is not in the zero oxidation state. The several Pd-O species identified are shown in Table I. Hence, in the case of Pd/CdS the XPS spectra were recorded only after argon-ion sputtering, in order to study the surface free of oxide
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TL;DR: For a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities.
Abstract: In this review, for a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities. Process parameters include presence or absence of (organic) sacrificial agents, applied pH, presence or absence of an air/inert atmosphere, metal precursor type and concentration, and temperature. Most intensively reviewed are studies concerning (i) TiO2; (ii) ZnO, focusing on Ag deposition; (iii) WO3, with a strong emphasis on the photodeposition of Pt; and (iv) CdS, again with a focus on deposition of Pt. Furthermore, a detailed overview is given of achievements in structure-directed photodeposition, which could ultimately be employed to obtain highly effective photocatalytic materials. Finally, we provide suggestions for improvements in description of the photodeposition methods applied when included in scientific papers.
648 citations
TL;DR: In this paper, a simple approach to autocatalytic reduction and decoration of Au, Pd, and Pt nanocrystals on biodegradable cellulose polymer coated with polypyrrole was reported.
Abstract: We report a simple approach to autocatalytic reduction and decoration of Au, Pd, and Pt nanocrystals on biodegradable cellulose polymer coated with polypyrrole. Cellulose was used as a template for the coating of polypyrrole. Reduction of different metals such as Au, Pd, and Pt and their decoration can be achieved through polypyrrole-coated cellulose fibers. Pre-selected bulk morphology of PdO/PdO2-embedded carbon was achieved through a microwave combustion method within one minute using the above-mentioned metal and polypyrrole-coated composite cellulose fibers. Synthesized Pd-decorated polypyrrole-coated cellulose fibers (Pd/py-cellulose) and microwave-ignited above mentioned (PdO/PdO2/C) materials provide a suitable catalyst for the degradation/reduction of methylene blue (waste water simulator) to leucomethylene blue at room temperature in aqueous media. At various concentrations, the material exhibits an overall reaction coefficient (ranging from 0.0183 to 0.1168 M−1 s−1), much greater than the self-degradation of methylene blue (MB) (0.00002 M−1 s−1). Through microwave ignition, the apparent increase in surface area of palladium results in a catalyst capable of high conversion (68.9%) at low concentrations.
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TL;DR: In this article, the major surface and interface modification strategies to improve the photoactivity and photostability of Cadmium sulfide-based photocatalysts are reviewed, and some perspectives are presented, highlighting the main challenges in further optimizing the performance and achieving industrial applications.
Abstract: Cadmium sulfide (CdS) is an important visible light–responsive semiconductor, but its photocatalytic activity is limited by the rapid recombination of photogenerated charge carriers both in the bulk and on the surface. Moreover, CdS suffers from poor stability owing to photocorrosion, which further hinders its practical applications. The aim of this chapter is to review the major surface and interface modification strategies to improve the photoactivity and photostability of CdS-based photocatalysts. These modification strategies can promote surface reaction kinetics (e.g., by loading cocatalysts and controlling the exposed facets), accelerate charge separation kinetics (e.g., by designing nanostructures with diverse dimensions and morphologies, introducing defects, creating solid solutions, building heterojunction and homojunction), and enhance the photostability (e.g., by utilizing sacrificial agents, fabricating p–n heterojunction or Z-scheme heterojunction, and creating covering layer). Finally, some perspectives are presented, highlighting the main challenges in further optimizing the performance of CdS-based photocatalysts and achieving industrial applications.
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TL;DR: In this paper, highly-dispersed Pd nanoparticles on single wall carbon nanohorn (Pd-SWCNH) and on oxidized SWCNH without an anti-aggregation agent were determined by electron microscopy.
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TL;DR: In this article, a study of catalysts based on a Ce0.72Zr0.18Pr0.1O2 solid solution with Pt, Pd, and Ru supported from acetylacetonate precursors showed their high activity in the processes of CO and methane oxidation.
Abstract: The study of catalysts based on a Ce0.72Zr0.18Pr0.1O2 solid solution with Pt, Pd, and Ru supported from acetylacetonate precursors showed their high activity in the processes of CO and methane oxidation. Transmission electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy were used for determining the nature of the active sites of the catalysts. The metal-support interaction effect, which increased in the order Ru < Pd < Pt, was found, and a relationship between the intensity of this interaction and the catalytic action was established.
9 citations
References
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TL;DR: In this article, the x-ray emission wavelengths have been reevaluated and placed on a consistent \AA{}* scale, which makes "best" use of all xray wavelength data, and also permits calculation of the probable error for each energy difference.
Abstract: All of the x-ray emission wavelengths have recently been reevaluated and placed on a consistent \AA{}* scale. For most elements these data give a highly overdetermined set of equations for energy level differences, which have been solved by least-squares adjustment for each case. This procedure makes "best" use of all x-ray wavelength data, and also permits calculation of the probable error for each energy difference. Photoelectron measurements of absolute energy levels are more precise than x-ray absorption edge data. These have been used to establish the absolute scale for eighty-one elements and, in many cases, to provide additional energy level difference data. The x-ray absorption wavelengths were used for eight elements and ionization measurements for two; the remaining five were interpolated by a Moseley diagram involving the output values of energy levels from adjacent elements. Probable errors are listed on an absolute energy basis. In the original source of the present data, a table of energy levels in Rydberg units is given. Difference tables in volts, Rydbergs, and milli-\AA{}* wavelength units, with the respective probable errors, are also included there.
1,598 citations
Book•
01 Jan 1983
TL;DR: Energy resources through photochemistry and catalysis as discussed by the authors have also been used for energy and mineral resources in the field of computer science. But, they have not been used in the area of renewable energy.
Abstract: energy resources through photochemistry and catalysis pdf ebook energy resources through photochemistry and catalysis ebook energy resources through photochemistry and catalysis energy resources through photochemistry and catalysis energy resources through photochemistry and catalysis energy resources through photochemistry and catalysis organometallics and catalysis pdf firebase light harvesting and energy transfer in laser dye-labeled nanotechnology in catalysis nanostructure science and free download section 4 1 energy and mineral resources kids guide to types of landforms childrens science nature photochemistry and photophysics of hyper porphyrins solar photochemistry office of science 2000 gmc w3500 manual quafe free download section 4 2 alternate energy resources homogeneous and heterogeneous photocatalysis springer free download energy and resources section 1 reinforcement malory and christianity essays on sir thomas malorys morte nazaryth [the exiled 1] (siren publishing everlasting free download energy resources wordsearch answers cad managers guidebook paycox photoelectrochemical reduction of co2 using silicate rock tier unit 3 1 day fourscorched earth ebook | ufcgymmatthews how to troubleshoot a tv receiver dioro bien dit french 2 workbook answers alongz size effects in photoprocesses on dispersed catalysts department of chemistry, university of texas, austin basic energy sciences overview
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TL;DR: In this article, photoetching of CdS microcrystals has been used to improve the efficiency of photochemical hydrogen production by irradiating suspensions of platinized cdS in various electrolyte solutions.
Abstract: Active photocatalysts for photochemical hydrogen production have been prepared by platinum deposition on microcrystals of CdS powders. Hydrogen produced by irradiating suspensions of platinized CdS in various electrolyte solutions (S/sup 2 -/, SO/sub 3//sup 2 -/, H/sub 2/PO/sup 2 -/) has been shown to be significantly improved by photoetching the CdS microcrystals. The efficiency of hydrogen formation in solutions containing S/sup 2 -/ is low due to the formation of disulfide ions. Additional of reducing agents such as sulfite or hypophosphite ions, which efficiently suppresses disulfide formation, allows hydrogen to evolve at a surprisingly high rate. In the case of a solution containing both S/sup 2/ and SO/sub 3//sup 2 -/ ions, the formation of thiosulfate is observed with a quantum yield of 0.25. In mixtures of sulfide and hypophosphite ions, phosphite and phosphate ions are the oxidation products. Hydrogen formation occurs in solutions containing SO/sub 3//sup 2 -/ ions only when the platinized CdS particles have previously been photoetched. Concomitant to the proton reduction, SO/sub 3//sup 2 -/ ions are oxidized to sulfate and dithionate. In 12 days, 9 L of H/sub 2/ was generated by irradiating 1 g of CdS/Pt suspended in an Na/sub 2/SO/sub 3/ solution. Aftermore » this period, the efficiency of the photocatalyst dropped to about 60% of the initial rate. The reaction parameters and the formation of the oxidation products have been investigated in detail. 57 references, 10 figures, 4 tables.« less
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TL;DR: In this article, surface composition and depth profile studies of hemiplated thin film CdS:CuzS solar cells have been carried out using XPS and Auger electron spectroscopy (AES) techniques.
Abstract: Surface composition and depth profile studies of hemiplated thin film CdS:CuzS solar cells have been carried out using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. These studies indicate that the junction is fairly diffused in the as-prepared cell. However, heat treatment of the cell at 210°C in air relatively sharpens the junction and improves the cell performance. Using the Cu(2p3p)/S(2p) ratio as well as the Cu(LVV)/(LMM) Auger intensity ratio, it can be inferred that the nominal valency of copper in the layers above the junction is Cut and it is essentially in the CUSS form. Copper signals are observed from layers deep down in the cell. These seem to appear mostly from the grain boundary region. From the observed concentration of Cd, Cu and S in these deeper layers and the Cu(LVV)/(LMM) ratio it appears that the signals from copper essentially originate partly from copper in CuS and partly from Cu2t trapped in the lattice. It is significant to note that the nominal valence state of copper changes rather abruptly from Cut to Cuz+ across the junction.
104 citations