Electron spectroscopy of platinum-oxygen surfaces and application to electrochemical studies

Kim, K. S.; Winograd, Nicholas; Davis, Robert Earl

doi:10.1021/ja00752a065

Cited by 390 publications

(185 citation statements)

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“…On the assumption that the ratio of the peak area of 4f 7/2 and 4f 5/2 is constant (1.33) for each platinum species, 53 the apparent spectra could be deconvoluted into three sets of peaks as shown Figure 5 with the parameters listed in Table 1. They were assigned to Pt 0 , Pt with adsorbed oxygen (PtO ads ), and oxidized Pt (PtO).…”

Section: Resultsmentioning

confidence: 99%

Role of Platinum Deposits on Titanium(IV) Oxide Particles: Structural and Kinetic Analyses of Photocatalytic Reaction in Aqueous Alcohol and Amino Acid Solutions

et al. 1997

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Photocatalytic reaction at 298 K by platinum-loaded titanium(IV) oxide (TiO 2 -Pt) particles suspended in deaerated aqueous solutions of 2-propanol or (S)-lysine (Lys) was investigated. The TiO 2 catalysts with various amounts of Pt loadings were prepared by impregnation from aqueous chloroplatinic acid solution onto a commercial TiO 2 (Degussa P-25) followed by hydrogen reduction at 753 K. The physical properties of deposited Pt, e.g., particle size, surface area, and electronic state, were studied respectively by transmission electron microscopy, volumetric gas adsorption measurement, and X-ray photoelectron spectroscopy as well as infrared spectroscopy of adsorbed carbon monoxide. The increase in Pt amount mainly resulted in an increase of the number of Pt deposits, not of their size. The catalysts were suspended in the aqueous solutions and photoirradiated at a wavelength >300 nm under an argon (Ar) atmosphere. The overall rate of photocatalytic reactions for both 2-propanol and Lys, corresponding to the rate of consumption of these substrates, was negligible without Pt loading, increased drastically with the loading up to ca. 0.3%, and was almost constant or a little decreased by the further loadings. However, the rate of formation of pipecolinic acid (PCA) from Lys was improved gradually with a increase of Pt loading up to ca. 2 wt %. These dependences were discussed as a function of Pt surface area, which is employed as a measure that includes the properties of both number and size of Pt deposits. For the photocatalytic dehydrogenation of 2-propanol, the rate dependence could be interpreted semiquantitatively with the model that only the TiO 2 particles loaded with at least one Pt deposit can photocatalyze, but the reaction rate is independent of the number of Pt deposits. Therefore, the overall rate is proportional to the number of Pt-loaded TiO 2 particles. On the other hand, for the interpretation of the rate of PCA and H 2 productions, the number of Pt deposits on each TiO 2 particle had to be taken into account. The efficient production of PCA at higher Pt loadings was attributed to the reduction of a Schiff base intermediate produced via oxidation of Lys with positive holes and subsequent intramolecular condensation at the Pt deposit that is close to the site for the oxidation. Otherwise, photoexcited electrons are consumed for H 2 production and the intermediate remains unreduced or undergoes further oxidation. It was suggested that the intermediate produced at the TiO 2 surface sites within a distance of several nanometers from the Pt deposit undergoes efficient reduction to PCA. Thus, the importance of the distribution of Pt deposits for the preparation of highly active and selective TiO 2 -Pt photocatalyst has been clearly demonstrated.

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Section: Resultsmentioning

confidence: 99%

Role of Platinum Deposits on Titanium(IV) Oxide Particles: Structural and Kinetic Analyses of Photocatalytic Reaction in Aqueous Alcohol and Amino Acid Solutions

et al. 1997

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“…In several studies a Pt 2+ state (e. g. PtO) was found in +1-1.8 eV relative to metallic Pt [64,65]. However numerous others [66,67] indicate PtO in a +2.4-3 eV distance and PtO 2 is observed in +3.6-4.5 eV distance [66,68]. Different surface-core-level-shift (SCLS) values were observed for adsorbed O 2 on Pt single crystals [67,69].…”

Section: High Pressure Xpsmentioning

confidence: 99%

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part I: Oxidation state and surface species on Pt/CeO2 under reaction conditions

Pozdnyakova

Teschner

Wootsch

et al. 2006

Journal of Catalysis

384

245

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The CO content of hydrogen feed to proton exchange membrane fuel cells (PEMFC) must be kept under 1-100 ppm for their proper operation. This can be achieved by using catalysts able to selectively oxidize CO in the presence of excess hydrogen (PROX). The present study reports on the mechanism of PROX reaction on Pt/CeO 2 catalyst, by using catalytic tests, in-situ DRIFTS, high-pressure XPS, HRTEM and TDS techniques. Bulk metallic, pronounced adsorbate-induced surface Pt and a small amount of oxidized Pt sites were detected by in-situ, high pressure XPS under PROX conditions. The pre-oxidized ceria surface was strongly reduced in pure H 2 but significantly re-oxidized under PROX conditions (i.e. O 2 +CO in excess hydrogen) at T=358 K. The remaining small amount of Ce 3+ decreased with increasing temperature. HRTEM found well-crystallized CeO 2 particles (8-10 nm) in the case of activated (pre-oxidized) sample that transformed in a large extent to an oxygen deficient ceria super-cell structure after PROX reaction. Metallic Pt particles (2-3 nm) and small (0.5-0.6 nm) Pt clusters were found by HRTEM. These findings were in accordance with the variations in relative intensity of the corresponding Pt-CO bands (DRIFTS). Different types of carbonate and formate species were detected (XPS and DRIFTS). Their possible role in the reaction mechanism is discussed. Resolved OH bands could not be found by DRIFT in the PROX reaction mixture indicating significant amount of adsorbed water in a hydrogen-bonded structure. Its presence seems to suppress hydrogen oxidation while CO oxidation still takes place, as the metallic particles are covered by CO (DRIFTS). The direct contribution of surface water in a low-temperature water-gas-shift (LTWGS) type reaction in the PROX mixture is proposed.

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“…However, after SnMe 4 was grafted onto Pt atoms in Pt/NaY zeolite, the binding energy of Pt (4f 7/2 ) split into 71.20 and 74.68 eV. 25,26 This change in the binding energy confirms that SnMe 4 reacts with Pt atoms in Pt/NaY zeolite, and shows that two different Pt species exist in the supercages of NaY zeolite. 27 This is in agreement with the above IR results of CO chemisorption.…”

Section: Co-tpd and Xps Characterization Of The Modified Samplementioning

confidence: 84%

Preparation and catalytic properties of a bimetallic SnPt complex in the supercages of NaY zeolite by use of surface organometallic chemistry

Zheng¹,

Wang²,

Fu³

et al. 2007

Applied Organom Chemis

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The grafting reaction of SnMe 4 on the surface of Pt/NaY zeolite was investigated in a 1.6 × 10 4 Pa hydrogen atmosphere. The chemical compositions, structure and properties of the resulting solid were characterized by in situ FTIR, ICP, XRD, XPS, temperature programmed decomposition and nitrogen adsorption. The results show that Pt atoms of Pt/NaY zeolite react with tetramethyltin to form a bimetallic Me 3 Sn-Pt surface species in the presence of hydrogen at 353 K. The reaction does not destroy the zeolite framework, while its surface properties are changed. The BET surface area and the pore volume of the zeolite decrease significantly. The CO chemisorption results and the XPS results show that the electronic properties of the modified Pt atoms on the surface of NaY zeolite are altered remarkably by the inductive effect of electron between Pt and methyl groups. The grafted product has excellent selective hydrogenation of furfural to furfuryl alcohol.

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Electron spectroscopy of platinum-oxygen surfaces and application to electrochemical studies

Cited by 390 publications

References 0 publications

Role of Platinum Deposits on Titanium(IV) Oxide Particles: Structural and Kinetic Analyses of Photocatalytic Reaction in Aqueous Alcohol and Amino Acid Solutions

Role of Platinum Deposits on Titanium(IV) Oxide Particles: Structural and Kinetic Analyses of Photocatalytic Reaction in Aqueous Alcohol and Amino Acid Solutions

Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part I: Oxidation state and surface species on Pt/CeO2 under reaction conditions

Preparation and catalytic properties of a bimetallic SnPt complex in the supercages of NaY zeolite by use of surface organometallic chemistry

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