{"title":"原位高分辨率x射线光电子能谱-表面反应的基本见解","authors":"Christian Papp, Hans-Peter Steinrück","doi":"10.1016/j.surfrep.2013.10.003","DOIUrl":null,"url":null,"abstract":"<div><p><span>Since the advent of third generation synchrotron light sources optimized for providing soft X-rays up to 2</span> <span><span>keV, X-ray photoelectron spectroscopy (XPS) has been developed to be an outstanding tool to study surface properties and surface reactions at an unprecedented level. The high resolution allows identifying various surface species, and for small molecules even the vibrational fine structure can be resolved in the XP spectra. The high photon flux reduces the required measuring time per spectrum to the domain of a few seconds or even less, which enables to follow surface processes in situ. Moreover, it also provides access to very small coverages down to below 0.1% of a monolayer, enabling the investigation of minority species or processes at defect sites. The photon energy can be adjusted according to the requirement of a particular experiment, i.e., to maximize or minimize the surface sensitivity or the photoionization<span> cross-section of the substrate or the adsorbate. For a few instruments worldwide, a next step forward was taken by combining in situ high-resolution spectrometers with supersonic </span></span>molecular beams. These beams allow to control and vary the kinetic and internal energies of the incident molecules and provide a local pressure of up to ~10</span><sup>−5</sup> <!-->mbar, which can be switched on and off in a controllable way, thus offering a well-defined time structure to study adsorption or reaction processes.</p><p><span>Herein, we will review some specific scientific aspects which can be addressed by in situ XPS in order to demonstrate the power and potential of the method: In particular, the following topics will be addressed: (1) The sensitivity of the binding energy to adsorption sites will be analyzed, using CO on metals as example. From measurements at different temperatures, the binding energy difference between different sites can be derived, and exchange processes between different adsorbate species at step edges can be followed. (2) The vibrational fine structure of adsorbed small hydrocarbon species on metal surfaces will be analyzed in detail. We will first introduce the linear coupling model, then discuss the properties of adsorbed methyl and of a number of other small hydrocarbons, and show that the vibrational signature can be used as fingerprint for identifying surface species. (3) It is demonstrated that the binding energy of equivalent atoms in a molecule can be differentially changed by adsorption to a substrate; this sensitivity to the local environment will be discussed for adsorbed ethylene, benzene and graphene. (4) By temperature programmed XPS, the thermal evolution of adsorbed species can be followed in great detail, allowing for the identification of reaction intermediates and the determination of their stabilities. (5) The investigation of reaction kinetics by isothermal XPS measurements will be discussed; here results for the </span>oxidation<span> of sulfur and of CO will be presented and the corresponding activation energies of the rate limiting steps will be determined.</span></p></div>","PeriodicalId":434,"journal":{"name":"Surface Science Reports","volume":null,"pages":null},"PeriodicalIF":8.2000,"publicationDate":"2013-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.surfrep.2013.10.003","citationCount":"79","resultStr":"{\"title\":\"In situ high-resolution X-ray photoelectron spectroscopy – Fundamental insights in surface reactions\",\"authors\":\"Christian Papp, Hans-Peter Steinrück\",\"doi\":\"10.1016/j.surfrep.2013.10.003\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p><span>Since the advent of third generation synchrotron light sources optimized for providing soft X-rays up to 2</span> <span><span>keV, X-ray photoelectron spectroscopy (XPS) has been developed to be an outstanding tool to study surface properties and surface reactions at an unprecedented level. The high resolution allows identifying various surface species, and for small molecules even the vibrational fine structure can be resolved in the XP spectra. The high photon flux reduces the required measuring time per spectrum to the domain of a few seconds or even less, which enables to follow surface processes in situ. Moreover, it also provides access to very small coverages down to below 0.1% of a monolayer, enabling the investigation of minority species or processes at defect sites. The photon energy can be adjusted according to the requirement of a particular experiment, i.e., to maximize or minimize the surface sensitivity or the photoionization<span> cross-section of the substrate or the adsorbate. For a few instruments worldwide, a next step forward was taken by combining in situ high-resolution spectrometers with supersonic </span></span>molecular beams. These beams allow to control and vary the kinetic and internal energies of the incident molecules and provide a local pressure of up to ~10</span><sup>−5</sup> <!-->mbar, which can be switched on and off in a controllable way, thus offering a well-defined time structure to study adsorption or reaction processes.</p><p><span>Herein, we will review some specific scientific aspects which can be addressed by in situ XPS in order to demonstrate the power and potential of the method: In particular, the following topics will be addressed: (1) The sensitivity of the binding energy to adsorption sites will be analyzed, using CO on metals as example. From measurements at different temperatures, the binding energy difference between different sites can be derived, and exchange processes between different adsorbate species at step edges can be followed. (2) The vibrational fine structure of adsorbed small hydrocarbon species on metal surfaces will be analyzed in detail. We will first introduce the linear coupling model, then discuss the properties of adsorbed methyl and of a number of other small hydrocarbons, and show that the vibrational signature can be used as fingerprint for identifying surface species. (3) It is demonstrated that the binding energy of equivalent atoms in a molecule can be differentially changed by adsorption to a substrate; this sensitivity to the local environment will be discussed for adsorbed ethylene, benzene and graphene. (4) By temperature programmed XPS, the thermal evolution of adsorbed species can be followed in great detail, allowing for the identification of reaction intermediates and the determination of their stabilities. (5) The investigation of reaction kinetics by isothermal XPS measurements will be discussed; here results for the </span>oxidation<span> of sulfur and of CO will be presented and the corresponding activation energies of the rate limiting steps will be determined.</span></p></div>\",\"PeriodicalId\":434,\"journal\":{\"name\":\"Surface Science Reports\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":8.2000,\"publicationDate\":\"2013-11-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1016/j.surfrep.2013.10.003\",\"citationCount\":\"79\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Surface Science Reports\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0167572913000241\",\"RegionNum\":1,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Surface Science Reports","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0167572913000241","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
In situ high-resolution X-ray photoelectron spectroscopy – Fundamental insights in surface reactions
Since the advent of third generation synchrotron light sources optimized for providing soft X-rays up to 2keV, X-ray photoelectron spectroscopy (XPS) has been developed to be an outstanding tool to study surface properties and surface reactions at an unprecedented level. The high resolution allows identifying various surface species, and for small molecules even the vibrational fine structure can be resolved in the XP spectra. The high photon flux reduces the required measuring time per spectrum to the domain of a few seconds or even less, which enables to follow surface processes in situ. Moreover, it also provides access to very small coverages down to below 0.1% of a monolayer, enabling the investigation of minority species or processes at defect sites. The photon energy can be adjusted according to the requirement of a particular experiment, i.e., to maximize or minimize the surface sensitivity or the photoionization cross-section of the substrate or the adsorbate. For a few instruments worldwide, a next step forward was taken by combining in situ high-resolution spectrometers with supersonic molecular beams. These beams allow to control and vary the kinetic and internal energies of the incident molecules and provide a local pressure of up to ~10−5 mbar, which can be switched on and off in a controllable way, thus offering a well-defined time structure to study adsorption or reaction processes.
Herein, we will review some specific scientific aspects which can be addressed by in situ XPS in order to demonstrate the power and potential of the method: In particular, the following topics will be addressed: (1) The sensitivity of the binding energy to adsorption sites will be analyzed, using CO on metals as example. From measurements at different temperatures, the binding energy difference between different sites can be derived, and exchange processes between different adsorbate species at step edges can be followed. (2) The vibrational fine structure of adsorbed small hydrocarbon species on metal surfaces will be analyzed in detail. We will first introduce the linear coupling model, then discuss the properties of adsorbed methyl and of a number of other small hydrocarbons, and show that the vibrational signature can be used as fingerprint for identifying surface species. (3) It is demonstrated that the binding energy of equivalent atoms in a molecule can be differentially changed by adsorption to a substrate; this sensitivity to the local environment will be discussed for adsorbed ethylene, benzene and graphene. (4) By temperature programmed XPS, the thermal evolution of adsorbed species can be followed in great detail, allowing for the identification of reaction intermediates and the determination of their stabilities. (5) The investigation of reaction kinetics by isothermal XPS measurements will be discussed; here results for the oxidation of sulfur and of CO will be presented and the corresponding activation energies of the rate limiting steps will be determined.
期刊介绍:
Surface Science Reports is a journal that specializes in invited review papers on experimental and theoretical studies in the physics, chemistry, and pioneering applications of surfaces, interfaces, and nanostructures. The topics covered in the journal aim to contribute to a better understanding of the fundamental phenomena that occur on surfaces and interfaces, as well as the application of this knowledge to the development of materials, processes, and devices. In this journal, the term "surfaces" encompasses all interfaces between solids, liquids, polymers, biomaterials, nanostructures, soft matter, gases, and vacuum. Additionally, the journal includes reviews of experimental techniques and methods used to characterize surfaces and surface processes, such as those based on the interactions of photons, electrons, and ions with surfaces.