An XPS evidence of the effect of the electronic state of Pd on CH4 oxidation on Pd/γ–Al2O3 catalysts

Corro, Grisel; Vázquez‐Cuchillo, O.; Bañuelos, Fortino; Fierro, J. L. G.; Azomoza, M.

doi:10.1016/j.catcom.2007.03.020

Cited by 21 publications

(11 citation statements)

References 20 publications

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“…According to the literature data, the binding energies of Pd 3d 5/2 in these catalysts at 337±0.2 and 338.2±0.2 eV are corresponding to PdO [35−37] and PdO 2 [37,38], respectively. -GD catalyst exhibited the best activity with the lowest average valence of palladium, we can deduce that the activity is related to the average valence of palladium in catalysts, which is similar to the conclusion in the references [39,40]. Besides, the low average valence of Palladium resulting from the interaction between PdO and supports would increase the decomposition temperature of PdO as shown in O 2 -TPD (Figure 4).…”

Section: X-ray Photoelectron Spectroscopy (Xps)supporting

confidence: 86%

A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

Pan

Zhang

Miao

et al. 2013

Journal of Energy Chemistry

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Section: X-ray Photoelectron Spectroscopy (Xps)supporting

confidence: 86%

A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

Pan

Zhang

Miao

et al. 2013

Journal of Energy Chemistry

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“…With the increase of H2S concentration, the XPS peak intensity of sulfur species increased gradually. At the same time, the Pd3d5/2 could be deconvoluted into two peaks at ~335.6 eV and ~337.5 eV which corresponded to metallic Pd 0 [45,46] and Pd4S [47,48], respectively. This indicated that Pd4S and metallic Pd 0 were the primary palladium species on the freshly prepared catalysts.…”

Section: Catalyst Characterizationmentioning

confidence: 95%

“…Therefore, used catalysts were further analyzed by XPS characterization, as shown in Figure 7. After curve fitting analysis, the Pd3d 5/2 could be deconvoluted into three peaks at~337.5 eV, 336.9 eV, and~335.6 eV, which were assigned to Pd 4 S [47,48], PdO [48], and metallic Pd 0 [45,46], respectively. The above characterization results revealed the fact that under the reaction conditions, the actual palladium species on the used catalyst surface should be Pd 4 S, PdO, and metal Pd 0 .…”

Section: Catalyst Characterizationmentioning

confidence: 99%

Pd4S/SiO2: A Sulfur-Tolerant Palladium Catalyst for Catalytic Complete Oxidation of Methane

Yuan

Jiang

et al. 2019

Catalysts

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Sulfur species (e.g. H2S or SO2) are the natural enemies of most metal catalysts, especiallypalladium catalysts. The previously reported methods of improving sulfur-tolerance were toeffectively defer the deactivation of palladium catalysts, but could not prevent PdO and carrierinteraction between sulfur species. In this report, novel sulfur-tolerant SiO2 supported Pd4Scatalysts (5 wt. % Pd loading) were prepared by H2S–H2 aqueous bubble method and applied tocatalytic complete oxidation of methane. The catalysts were characterization by X-ray diffraction,Transmission electron microscopy, X-ray photoelectron Spectroscopy, temperature-programmedoxidation, and temperature-programmed desorption techniques under identical conditions. Thestructural characterization revealed that Pd4S and metallic Pd0 were found on the surface of freshlyprepared catalysts. However, Pd4S remained stable while most of metallic Pd0 was converted toPdO during the oxidation reaction. When coexisting with PdO, Pd4S not only protected PdO fromsulfur poisoning, but also determined the catalytic activity. Moreover, the content of Pd4S could beadjusted by changing H2S concentration of H2S–H2 mixture. When H2S concentration was 7 %, thePd4S/SiO2 catalyst was effective in converting 96% of methane at the 400 °C and also exhibitedlong-term stability in the presence of 200 ppm H2S. A Pd4S/SiO2 catalyst that possesses excellentsulfur-tolerance, oxidation stability, and catalytic activity has been developed for catalyticcomplete oxidation of methane.

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“…In fact, there are a few reports in which it is stated that surface palladium oxide is responsible for oxidation activity rather than metallic Pd, [24][25][26][27] whereas Goodman et al claim that metallic Pd is active even under high-pressure conditions. [28] Further, a small amount of Pd (typically 1 wt %) used in automotive catalytic converters tend to be nanoparticles, enriched with defects, and hence, O diffusion into subsurfaces and surface oxidation of Pd is inevitable with net oxidizing exhaust composition in the present generation fuel-lean automobiles.…”

Section: Near-ambient Pressure Photoelectron Spectroscopy Studiesmentioning

confidence: 99%

Can We Shift and/or Broaden the Catalysis Regime towards Ambient Temperature?

2015

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An attempt was made to shift the temperature regime of oxidation catalysis towards ambient temperatures by employing surface modification (SM) as a handle. Systematic SM of Pd(111) was performed by O-atom diffusion into the subsurfaces. Virgin and modified Pd(111) catalysts were evaluated for CO oxidation. Typical CO poisoning observed on virgin surfaces was partially lifted, and ambient CO oxidation was observed on the modified surfaces. CO oxidation was followed by the molecular beam method and near-ambient pressure (NAP) photoelectron spectroscopy under different pressure regimes. UV valence band spectral analysis of the SM and the CO + O 2 reaction on modified Pd (111) surfaces under NAP conditions demonstrated changes in the electronic structures of the surfaces with a change in surface potential by 0.35 eV and directly probed CO 2 formation under the reaction conditions. Supported metal catalysts may be subjected to SM and evaluated for a shift in the catalysis regime for many different reactions.[a] Prof.

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An XPS evidence of the effect of the electronic state of Pd on CH4 oxidation on Pd/γ–Al2O3 catalysts

Cited by 21 publications

References 20 publications

A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

Pd4S/SiO2: A Sulfur-Tolerant Palladium Catalyst for Catalytic Complete Oxidation of Methane

Can We Shift and/or Broaden the Catalysis Regime towards Ambient Temperature?

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