Influence of modifying additives on electronic state of supported gold

Pestryakov, Alexey; Лунин, В. В.; Харланов, А. Н.; Kochubey, D.I.; Bogdanchikova, Nina; Stakheev, A. Yu.

doi:10.1016/s0022-2860(02)00402-7

Cited by 62 publications

(40 citation statements)

References 24 publications

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“…245 nm, which can be assigned to electronic transition of d-d type in the Fe 3+ ion and is ascribed to the E g fi T 2g transition [53,54]. For those samples that did not undergo further reactions, an absorption band at about 385 nm can be observed, which corresponds to oxidized states of gold in the form of Au + and Au n d+ [55]. The metallic gold peak, known to be located between 520-570 nm for gold particles on metal oxides [28,56] is found only on the parent catalyst.…”

Section: Co Oxidation On Au/fe 2 Omentioning

confidence: 97%

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

et al. 2007

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We compare the activity and relevant gold species of nanostructured gold-cerium oxide and gold-iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH ‡12. Both parent and leached catalysts were investigated. The activity of the leached gold-iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H 2 up to 400°C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold-ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV-Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.

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Section: Co Oxidation On Au/fe 2 Omentioning

confidence: 97%

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

et al. 2007

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“…Based on our work [22,37,38,65,64,69], as well as on analysis of the literature data [19,26,35,36 Figure 6. IR spectra of CO (equilibrium pressure of 1.1 kPa) adsorbed at room temperature on Au/NaY zeolite sample subjected to various pretreatments.…”

mentioning

confidence: 89%

Characterization of the Oxidation States of Supported Gold Species by IR Spectroscopy of Adsorbed CO

Mihaylov¹,

Knözinger²,

Hadjiivanov

et al. 2007

Chemie Ingenieur Technik

152

139

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The use of IR spectroscopy of adsorbed CO for determination of gold speciation on supported gold catalysts is reviewed. Different ionic and metallic sites (Au 3+ , Au + , Au 0 , and Au -) can be differentiated on the basis of the frequency and stability of their surface carbonyl species formed after CO adsorption. In addition, the study of CO adsorption and reaction with other gases can provide unique information on the mechanisms of catalytic reactions with participation of CO. Finally, results from complementary techniques such as X-ray absorption spectroscopy, also useful for determination of gold oxidation state, are briefly considered.

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“…The first band around 250 nm is assigned to the Au 3+ ions 28 while the band from 280-380 nm is referred to Au clusters (Au n , 1 < n < 10). 29,30 The SPR band of Au 0 appears at 550 nm for both samples, however, the band is less define in DP2 C11 (Fig. 1).…”

Section: Resultsmentioning

confidence: 89%

Synthesis of Au/Al₂O₃ Nanocatalyst and its Application in the Reduction of p‐Nitrophenol

Yazid

Adnan

Farrukh

et al. 2011

J Chinese Chemical Soc

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Gold (Au) nanoparticles supported on alumina (Al 2 O 3 ) were prepared at several pH levels via the deposition-precipitation (DP) method. The effects of pH at below and above the isoelectric point (IEP) of Al 2 O 3 as well as the pH adjustment before and after the addition of the support into the gold chloride solution were investigated. The results revealed the formation of cationic, clusters and metallic Au on alumina. The catalytic activity of these species was tested in the reduction of p-nitrophenol (p-NP) using hydrazine as a reductant. The catalytic reaction was monitored spectrophotometerically and the highest rate constant (k) achieved based on pseudo first order kinetic model was 12.7´10 -3 s -1 . Structural and elemental characterizations of the supported gold nanoparticles were carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-rays (EDX), atomic absorption spectrometry (AAS), and ultraviolet-visible spectroscopy (UV-Vis).Keywords: Gold; Alumina; Nanoparticles; Catalysis; Kinetics; Nitrophenol; Hydrazine. INTRODUCTIONMany methods for the preparation of metal and metal oxides nanoparticles are known.1 Supported Au nanoparticles prepared by the deposition-precipitation (DP) method were first proposed by Haruta and co-workers. 13 are reported to produce highly active catalysts in many reactions. However, when alumina was used as the support (IEP = 8-9), the resulted catalysts was found to be either very active or inactive under certain conditions during CO oxidation at room temperature. 14-16p-Nitrophenol is among the most common organic pollutants in agricultural wastewaters and industrial. The released of p-nitrophenol into the environment causes harmful effect particularly to biological systems due to its toxicity. As a result, many methods have been developed to remove the hazardous p-nitrophenol such as by photocatalytic degradation, 17 The Au/Al 2 O 3 obtained were analyzed by diffuse reflectance UV-visible (DRS UV-Vis) spectrometer -Perkin Elmer Lambda 35 with KBr powder as reference, powder X-ray diffraction (XRD) using PANanalytical diffractometer (diffraction patterns were compared using the standard database from International Centre Diffraction Data (ICDD)), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM observation was performed for the samples dried on carbon-coated copper grids. The size distribution of the Au nanoparticles was determined from at least about 200 particles. The elemental composition of Au was analyzed using a Perkin Elmer AAnalyst 200 atomic absorption spectrometer at a wavelength of 243 nm. 26 The Au loading of the samples is ex- Catalytic testA mixture of 1 mg gold nanocatalyst, 1.5 mL hydrazine (0.3 mM) and 1.5 mL solution of p-nitrophenol (0.1 mM) was added into a 3 mL cuvette at room temperature. The catalytic activity was determined using UV-Vis spectrophotometer (Perkin Elmer Lambda 25 UV-Vis) by measuring the change in absorbance at 400 nm...

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Influence of modifying additives on electronic state of supported gold

Cited by 62 publications

References 24 publications

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Characterization of the Oxidation States of Supported Gold Species by IR Spectroscopy of Adsorbed CO

Synthesis of Au/Al₂O₃ Nanocatalyst and its Application in the Reduction of p‐Nitrophenol

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Influence of modifying additives on electronic state of supported gold

Cited by 62 publications

References 24 publications

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Characterization of the Oxidation States of Supported Gold Species by IR Spectroscopy of Adsorbed CO

Synthesis of Au/Al2O3 Nanocatalyst and its Application in the Reduction of p‐Nitrophenol

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Synthesis of Au/Al₂O₃ Nanocatalyst and its Application in the Reduction of p‐Nitrophenol