XPS characterization

C. Morant, J. Andrey, P. Prieto, D. Mendiola, ).M. Sanz, E. Elizalde, XPS characterization of nitrogen-doped carbon nanotubes., Physica Status Solidi a-Applications and Materials Science, vol. 203, pp. 1069-1075, 2006. 

In this chapter, two carbon-supported PtSn catalysts with core-shell nanostructure were designed and prepared to explore the effect of the nanostructure of PtSn nanoparticles on the performance of ethanol electro-oxidation. The physical (XRD, TEM, EDX, XPS) characterization was carried out to clarify the microstructure, the composition, and the chemical environment of nanoparticles. The electrochemical characterization, including cyclic voltammetry, chronoamperometry, of the two PtSn/C catalysts was conducted to characterize the electrochemical activities to ethanol oxidation. Finally, the performances of DEFCs with PtSn/C anode catalysts were tested. The microstmc-ture and composition of PtSn catalysts were correlated with their performance for ethanol electrooxidation. 

This chapter deals with the selective preparation, TEM/EXAFS/XPS characterization and catalysis of mono- and bimetallic nanowires and nanoparticles highly ordered in silica FSM-16, organosilica HMM-1 and mesoporous silica thin films. The mechanism of nanowire formation is discussed with the specific surface-mediated reactions of metal precursors in the restraint of nanoscale void space of mesoporous silica templates. The unique catalytic performances of nanowires and particles occluded in mesoporous cavities are also reviewed in terms of their shape and size dependency in catalysis as well as their unique electronic and magnetic properties for the device application. 

Marino GEB, Nascente PAP, Biaggio SR, Rocha-Pilho RG, Bocchi N (2004) XPS characterization of anodic titanium oxide films grown in phosphate buffer solutions. Thin Solid Pilms 468 109-112... 

Goodby BE, Pemberton JE. XPS characterization of a commercial Cu/Zn0/Al203 catalyst - effects of oxidation, reduction, and the steam reformation of methanol. Appl Spectrosc. 1988 42(5) 754-60. 

An example illustrating the value of this approach is the work demonstrating the pressure gap effect in CO oxidation on Ru(0001). By use of ex situ TPD, STM, LEED, and XPS characterization, it was shown that the Ru(0001) surface, which appears to be inactive in surface-science investigations, is in reality a more efficient catalyst than platinum, because the active oxygen-rich phase cannot form under UHV conditions (Bottcher et al., 1997 Over et al., 2000, 2001). 

XPS characterization of TiOx/Rh samples after their exposure to synthesis gas under reaction conditions showed that a significant fraction of the titanium ions were still in the Ti3+ state. A summary of these observations is given in Table 1. It is evident that... 

In spite of this drawback, there is still much to be gained from XPS characterization of supported metal catalysts. Among these are the interconversion of metal salts into oxide and metal during catalyst pretreatment, the identification of poisons, and the distribution of metal within a zeolite or a porous pellet. 

Selective oxidation of hydrocarbons is of key importance in functionalization of hydrocarbon molecules. It is always a multi-step process with consecutive abstraction of hydrogen and addition of oxygen atoms. The difficulty of this reaction is, undoubtedly, that the process should go through these many steps, but also should stop at the desired product. Such requirements can be met by complex mixed-metal oxides, and the XPS characterization of two selected examples is briefly reviewed here. 

It was also observed in this work that Li and/or Li oxides appeared red under Ar ion bombardment. In the energy range of 500 to 2000 eV, the brightness of the red color increased with the ion energy. This provided another means to detect the presence of Li (or Li oxide). In one experiment, a clean Ag substrate was covered by a multilayer Li film (95% by AES) and then exposed to THF at 110 K. After about two hours (one hour for sample warm-up and the other for XPS characterization of the surface), the sample was placed under the Ar ion beam for cleaning. It took about 2 minutes to eliminate the Li layer (or Li oxide layer) on the surface by Ar ion bombardment... 

X-ray ray photoelectron spectroscopy (XPS) characterizes the chemical state and elemental abundance of the near-surface by measuring the kinetic energy and intensity of photoelectrons excited by irradiation of a sample (Raeburn et al. 1997b). Excellent reviews of the principles and instrumentation for XPS can be found in Hochella (1988), Turner and Schreifels (2000), and Tonner et al. (1999). 

Table 1. BET, ICP-AES and XPS characterization results of the various Au/TiOj samples.

Table 2. ICP-AES, XPS characterization and catalytic results of Au/Sn02 samples prepared by the Haruta and the ureacetate methods.

The surface composition of the fresh samples with exchange levels less than 100% is similar to that obtained by chemical analysis whereas for the overexchanged HZSM-5 sample XPS shows a surface enrichment in copper species. Moreover the copper seems to be more dispersed across the zeolite crystal as a result of dehydration. Further details and results of the XPS characterization will be reported elsewhere [8]. 

It was previously proposed that surface-carbonate compounds are reaction intermediates during catal34ic soot combustion (1,2). In this vein. High Frequency CO2 Pulses technique provides not only information about the stability of the surface, but also about the dynamics of the intermediate compound formation and decomposition. While XPS characterization shows that K/La surface ratio increases when increasing calcination temperature, results shown in Fig. 1 indicate that the CO2- surface interaction decreases. 

G. Granozzi, A. Glisenti, and G. D. Soraru, XPS characterization of mixed carbides obtained from polymer precursors. Mater. Res. Soc. Symp. Proc., 1990, 180, 811-814. 

Porte-Durrieu, M. C., Labrugere, C., Villars, F., Lefebvre, F., Dutoya, S., Guette, A., Btxdenave, L., and Baquey, C. (1999), Development of RGD peptides grafted onto silica surfaces XPS characterization and human endothelial cell interactions, J. Biomed. Mater. Res. 46(3) 368-375. 

PI-5878 films cured to 380°C in an oven were the substrates onto which 1.5 nm Cu and 1.5 nm Ni were deposited. XPS characterizations were performed before and after temperature-humidity (80°C-80%) exposure for 500 hours. In addition, a thick layer of Cu was evaporated onto one-half... 

Ohwaki T, Ishida H, Comparison between FT-IR and XPS characterization of carbon fiber surfaces, J Adhes, 52(1-4), 167 186, 1995. 

Pradier, C M., Costa, D., Rubio, C., Compere, C, Marcus, P. (2002) Role of salts on BSA adsorption on stainless steel in aqueous solutions. I. FT-IRRAS and XPS characterization. Surf Interface Anal., 34, 50-54. 

An XPS characterization of snrface composition and chemistry of a vinyl-pyridine-divinyl benzene copolymer and its chars obtained under different conditions (of temperature and atmosphere) was carried out by Lahaye and coworkers [28,31], Separation and identification of different types of heterocyclic nitrogen was carried out by fitting the Nj envelope, and at least six different forms of pyridinic nitrogen were proposed to exist. This study offers a good example of a methodology that can be applied to address such complex analytical challenges. 

---