Role of PdAg interface in Pd-Ag/SiO2 bimetallic catalysts in low-temperature oxidation of carbon monoxide

Bondarchuk, Ivan S.; Mamontov, G. V.

doi:10.1134/s0023158415030027

Cited by 25 publications

(8 citation statements)

References 44 publications

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“…For Ag/Mg/TiO 2 , there is a combination of a curve with a maximum (at low temperatures) and an S-shaped curve (at high temperatures). This effect, caused by both supported silver [2,16] and gold [37,38,39,40,41] catalysts, is explained in the literature as due to the activity of small clusters and larger particles, at low temperatures and at high temperatures, respectively. It can be seen that light-off curves for as-prepared Ag/Ce/TiO 2 and Ag/Fe/TiO 2 samples are similar; consequently, the contents of active species in them were comparable (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

“…Undetected small silver clusters have been suggested as the source of specific catalytic properties [1,2,3,4]. Flytzani-Stephanopoulos et al [33] explained the catalytic properties in the reduction of NO with methane by the coexistence of highly dispersed clusters (<2 nm) of oxidized silver and embedded Ag ions, which are active in selective reduction of CH 4 , but low active in CH 4 combustion.…”

Section: Resultsmentioning

confidence: 99%

“…The discovery of the extraordinary catalytic activity of gold nanoparticles for oxidation reactions compared to that of the bulk metal sparked the interest on the influence of the metal particle size at the nanometer scale on the catalytic performance of noble metal-based catalysts. In the literature, there are publications describing catalysts active at low temperature that contain both particles undetectable by ТЕМ and, in the other extreme, very large particles [1,2,3,4,5,6,7,8]. Difficulties in the interpretation of such results are associated with the limited information provided by the routine physical and chemical research methods of characterization (e.g., XRD and TEM).…”

Section: Introductionmentioning

confidence: 99%

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Identification of Subnanometric Ag Species, Their Interaction with Supports and Role in Catalytic CO Oxidation

et al. 2016

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Abstract:The nature and size of the real active species of nanoparticulated metal supported catalysts is still an unresolved question. The technique of choice to measure particle sizes at the nanoscale, HRTEM, has a practical limit of 1 nm. This work is aimed to identify the catalytic role of subnanometer species and methods to detect and characterize them. In this frame, we investigated the sensitivity to redox pretreatments of Ag/Fe/TiO 2 , Ag/Mg/TiO 2 and Ag/Ce/TiO 2 catalysts in CO oxidation. The joint application of HRTEM, SR-XRD, DRS, XPS, EXAFS and XANES methods indicated that most of the silver in all samples is in the form of Ag species with size <1 nm. The differences in catalytic properties and sensitivity to pretreatments, observed for the studied Ag catalysts, could not be explained taking into account only the Ag particles whose size distribution is measured by HRTEM, but may be explained by the presence of the subnanometer Ag species, undetectable by HRTEM, and their interaction with supports. This result highlights their role as active species and the need to take them into account to understand integrally the catalysis by supported nanometals.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Identification of Subnanometric Ag Species, Their Interaction with Supports and Role in Catalytic CO Oxidation

et al. 2016

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“…The H 2 -TPR profile of the sample prepared by using the DS_N 2 H 4 method demonstrates a broad positive peak of H 2 consumption with a maximum at 176 • C (Figure 6) and can be attributed to the reduction of highly dispersed Ag-Pd alloy NPs [75]. The absence of hydrogen absorbance by the IWI_H 2 sample can be connected with the low temperature of oxidative pretreatment [76] that is not sufficient for bulk oxidation of the relatively large NPs presented in this material.…”

Section: Acid and Redox Propertiesmentioning

confidence: 97%

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid

et al. 2020

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Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH3) and temperature-programmed reduction (TPR-H2) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

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“…The arrangement of high index facets of the nanocatalyst exhibits faster catalytic performance than the regular facets that contradict the expression of high density of steps and ledges that lead to the promotion of active sites for breaking the chemical bonds [11]. The Pd based bimetallic forms of nanostructures such as Pd-Ni, Pd-Cu, Pd-Pt, Pd-Au, and Pd-Ag play an extensive role in chemical reactions such as reduction of oxygen [12], CO 2 hydration [13], CO reduction [14,15], hydration of nitrophenol (4-NP) [16,17], dry reforming reaction [18], and dechlorination process [19]. The reduction of industrial pollutants such as 4-NP with the accomplishment of reaction in the presence of the metal catalyst is of interest in a hybrid platform [20].…”

Section: Introductionmentioning

confidence: 99%

Immobilized Pd-Ag bimetallic nanoparticles on polymeric nanofibers as an effective catalyst: effective loading of Ag with bimetallic functionality through Pd nucleated nanofibers

2018

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Here, we present a precise process for synthesizing Pd-Ag bimetallic nanoparticles (NPs) onto polymeric nanofibers by decorating Pd-NPs through atomic layer deposition followed by a chemical reduction process for tagging Ag nanostructures with bimetallic functionality. The results show that Pd-NPs act as a nucleation platform for tagging Ag and form Pd-Ag bimetallic NPs with a monodisperse nature with significant catalytic enhancement to the reaction rate over the bimetallic nature of the Pd-Ag ratio. A Pd-NP decorated polymeric nanofibrous web acts as an excellent platform for the encapsulation or interaction of Ag, which prevents agglomeration and promotes the interaction of Ag ions only on the surface of the Pd-NPs. We observed an effective reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride (NaBH) to access the catalytic activity of Pd-Ag bimetallic NPs on a free-standing flexible polymeric nanofibrous web as a support. The captive formation of the polymeric nanofibrous web with Pd-Ag bimetallic functionality exhibited superior and stable catalytic performance with reduction rates of 0.0719, 0.1520, and 0.0871 min for different loadings of Ag on Pd decorated nanofibrous webs such as Pd/Ag(0.01), Pd/Ag(0.03), and Pd/Ag(0.05), respectively. The highly faceted Pd-Ag NPs with an immobilized nature improves the catalytic functionality by enhancing the binding energy of the 4-NP adsorbate to the surface of the NPs. With the aid of bimetallic functionality, the nanofibrous web was demonstrated as a hybrid heterogeneous photocatalyst with a 3.16-fold enhancement in the reaction rate as compared with the monometallic decorative nature of NaBH as a reducing agent. The effective role of the monodisperse nature of Pd ions with an ultralow content as low as 3 wt% and the tunable ratio of Ag on the nanofibrous web induced effective catalytic activity over multiple cycles.

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Role of PdAg interface in Pd-Ag/SiO2 bimetallic catalysts in low-temperature oxidation of carbon monoxide

Cited by 25 publications

References 44 publications

Identification of Subnanometric Ag Species, Their Interaction with Supports and Role in Catalytic CO Oxidation

Identification of Subnanometric Ag Species, Their Interaction with Supports and Role in Catalytic CO Oxidation

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid

Immobilized Pd-Ag bimetallic nanoparticles on polymeric nanofibers as an effective catalyst: effective loading of Ag with bimetallic functionality through Pd nucleated nanofibers

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