CO-free hydrogen production over Au/CeO2–Fe2O3 catalysts: Part 1. Impact of the support composition on the performance for the preferential CO oxidation reaction

Tabakova, T.; Avgouropoulos, George; Manzoli, Maela; Boccuzzi, F.; Tenchev, K.; Vindigni, Floriana; Ioannides, Theophilos

doi:10.1016/j.apcatb.2010.10.016

Cited by 90 publications

(48 citation statements)

References 53 publications

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“…This is not surprising since the expected oxidation state of Fe 3+ also should enhance oxygen vacancy formation according to Equation (3), assuming that Fe 3+ (crystal radius VIII = 0.092 nm [16]) substitutes for Ce 4+ (crystal radius VIII = 0.111 nm [16]). Although the mismatch is ~17%, which is slightly higher than that suggested for extensive solid solubility (15%) [17], the formation of CeyFe1−yO2−x solid solution has been reported previously [33,34]. However, the substitution of Ce 3+ by Fe 3+ is much less likely owing to the large size of the former (crystal radius VIII = 0.1283 nm [16]) and the associated ~28% mismatch.…”

Section: Water Absorptionmentioning

confidence: 62%

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

et al. 2017

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Abstract:The present work describes the effects of water on Fe-doped nanoparticulate CeO 2 , produced by flame spray pyrolysis, which represent a critical environmental issue because CeO 2 is not stable in typical atmospheric conditions. It is hygroscopic and absorbs~29 wt % water in the bulk when exposed to water vapor but, more importantly, it forms a hydrated and passivating surface layer when immersed in liquid water. In the latter case, CeO 2 initially undergoes direct and/or reductive dissolution, followed by the establishment of a passivating layer calculated to consist of~69 mol % solid CeO 2 ·2H 2 O and~30 mol % gelled Ce(OH) 4 . Under static flow conditions, a saturated boundary layer also forms but, under turbulent flow conditions, this is removed. While the passivating hydrated surface layer, which is coherent probably owing to the continuous Ce(OH) 4 gel, would be expected to eliminate the photoactivity, this does not occur. This apparent anomaly is explained by the calculation of (a) the thermodynamic stability diagrams for Ce and Fe; (b) the speciation diagrams for the Ce 4+ -H 2 O, Ce 3+ -H 2 O, Fe 3+ -H 2 O, and Fe 2+ -H 2 O systems; and (c) the Pourbaix diagrams for the Ce-H 2 O and Fe-H 2 O systems. Furthermore, consideration of the probable effects of the localized chemical and redox equilibria owing to the establishment of a very low pH (<0) at the liquid-solid interface also is important to the interpretation of the phenomena. These factors highlight the critical importance of the establishment of the passivating surface layer and its role in photocatalysis. A model for the mechanism of photocatalysis by the CeO 2 component of the hydrated phase CeO 2 ·2H 2 O is proposed, explaining the observation of the retention of photocatalysis following the apparent alteration of the surface of CeO 2 upon hydration. The model involves the generation of charge carriers at the outer surface of the hydrated surface layer, followed by the formation of radicals, which decompose organic species that have diffused through the boundary layer, if present.

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Section: Water Absorptionmentioning

confidence: 62%

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

et al. 2017

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“…Several catalytic systems have been reported for use in the PROX reaction; they can be classified into three groups [11]: i) Pt, Ru and Rh supported catalysts [12,13]; ii) gold supported catalysts [14,15] iii) and copper-cerium oxide based catalysts. The last group has been thoroughly studied [8,16,17] and is well-known for presenting considerably higher selectivity to CO oxidation than the Pt-based catalysts at comparable conversion levels.…”

Section:  mentioning

confidence: 99%

“…The last group has been thoroughly studied [8,16,17] and is well-known for presenting considerably higher selectivity to CO oxidation than the Pt-based catalysts at comparable conversion levels. As regards the gold supported catalysts, they are very active, especially at low temperature which is one of the challenges to be overcome when designing PROX catalysts [14,15]. Combining copper and gold on several catalytic supports has been considered in some recent studies [18][19][20][21][22][23].…”

Section:  mentioning

confidence: 99%

Gold supported on CuOx/CeO2 catalyst for the purification of hydrogen by the CO preferential oxidation reaction (PROX)

Laguna

Hernández

Arzamendi

et al. 2014

Fuel

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Hydrogen produced from the conversion of hydrocarbons or alcohols contains variable amounts of CO that should be removed for some applications such as feeding lowtemperature polymer electrolyte membrane fuel cells (PEMFCs). The CO preferential oxidation reaction (PROX) is particularly well-suited for hydrogen purification for portable and on-board applications. In this work, the synthesis and characterization by XRF, BET, XRD, Raman spectroscopy and H 2 -TPR of a gold catalyst supported on a copper-cerium mixed oxide (AuCeCu) for the PROX reaction are presented. The comparison of this catalyst with the copper-cerium mixed oxide (CeCu) revealed that the experimental procedure used for the deposition of gold gave rise to the loss of reducible material by copper lixiviation. However, the AuCeCu solid was more active for CO oxidation at low temperature. A kinetic study has been carried over the AuCeCu catalyst for the PROX reaction and compared with that of the CeCu catalyst. The main difference between the models affected the contribution of the CO adsorption term. This fact may be related to the surface electronic activity produced by the interaction of the cationic species in the AuCeCu solid, able to create more active sites for the CO adsorption and activation in the presence of gold.

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“…For deposited platinum systems an additional factor is the nature and redox state of the support. Recently, much attention has been paid to the Pt/CeO 2 systems, since the redox ability of ceria makes them efficient catalysts of various industrial processes, such as preferential CO oxidation, 11,12 water gas shift reaction, 13 conversion of automotive exhaust gases into harmless ones, 14,15 reforming of alcohols, 16 conversions in fuel cell catalysts, 17 etc. The catalytic role of ceria is commonly considered to be related to its reducibility at elevated temperature.…”

Section: Introductionmentioning

confidence: 99%

Can the state of platinum species be unambiguously determined by the stretching frequency of an adsorbed CO probe molecule?

Aleksandrov

Neyman

Hadjiivanov

et al. 2016

Phys. Chem. Chem. Phys.

136

128

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Electronic Supplementary Information (ESI) available: Information includes sketches of all modeled Pt8(CO) complexes in gas phase and some of their energetic and structural characteristics, structure of e-reg/(CO)2 complex, and figure with the changes of the CO stretching frequency versus oxidation state and Bader charge of mononuclear platinum species. See DOI: 10.1039/x0xx00000x The paper addresses possible ambiguities in determination of the state of platinum species by the stretching frequency of a CO probe, which is a common technique for characterization of platinum-containing catalytic systems. We present a comprehensive comparison of the available experimental data with our theoretical modeling (density functional) results of pertinent systems -platinum surface, nanoparticles and clusters as well as reduced or oxidized platinum moieties on ceria support. Our results for CO adsorbed on-top on metallic Pt . This trend corroborates the Kappers-van der Maas correlation derived from analysis of experimental stretching frequency of CO adsorbed on platinum-containing samples on different supports. We also analyzed the effect of the charge of platinum species on the CO frequency. Based on the calculated vibrational frequencies of CO in various model systems, we concluded that the actual state of the platinum species may be mistaken based only on the measured value of the C-O vibrational frequency due to overlapping regions of frequencies corresponding to different types of species. In order to identify the actual state of platinum species one has to combine this powerful technique with other approaches.

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CO-free hydrogen production over Au/CeO2–Fe2O3 catalysts: Part 1. Impact of the support composition on the performance for the preferential CO oxidation reaction

Cited by 90 publications

References 53 publications

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Gold supported on CuOx/CeO2 catalyst for the purification of hydrogen by the CO preferential oxidation reaction (PROX)

Can the state of platinum species be unambiguously determined by the stretching frequency of an adsorbed CO probe molecule?

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