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Interfaces: Adsorption, Reactions, Films, Forces, Measurement Techniques, Charge Transfer, Electrochemistry, Electrocatalysis, Energy Production and Storage
X-ray Photoelectron Spectroscopy studies of nanoparticles dispersed in static liquid Luan Nguyen, Paul (Pengcheng) Tao, Huimin Liu, Mohamed Al-Hada, Matteo Amati, Hikmet Sezen, Luca Gregoratti, Yu Tang, Stephen D. House, and Franklin (Feng) Tao Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.8b00806 • Publication Date (Web): 22 May 2018 Downloaded from http://pubs.acs.org on May 22, 2018
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X-ray Photoelectron Spectroscopy studies of nanoparticles dispersed in static liquid Luan Nguyen,¶ Paul (Pengcheng) Tao,¶ Huimin Liu, ¶ Mohamed Al-Hada,╪ Matteo Amati, ╪ Hikmet Sezen, ╪ Luca Gregoratti,╪ Yu Tang¶, Steven D. House, Franklin (Feng) Tao,¶* Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS 66045, USA¶ Elettra - Sincrotrone Trieste ScPA, Trieste 34012, Italy╪ Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
Abstract For nanoparticles active for chemical and energy transformations in liquid environment, chemistries of surface or near-surface regions of these catalyst nanoparticles in liquid are crucial for fundamentally understanding their catalytic performances at a molecular level. Compared to catalysis at a solid-gas interface, there is very limited information on surface of these catalyst nanoparticles under working condition or during catalysis. Photoelectron spectroscopy is a surface-sensitive technique; however, it is challenging to study the surfaces of catalyst nanoparticles dispersed in liquid due to the short inelastic mean free path of photoelectrons travelling in liquid. Here we report a method for tracking surface of nanoparticles dispersed in liquid by employing graphene layers as an electrontransparent membrane to separate liquid containing solvent, catalyst nanoparticles, and reactants from the high-vacuum environment of photoelectron spectrometer. The surfaces of Ag nanoparticles dispersed in liquid sealed in such a graphene membrane liquid cell were successfully characterized using photoelectron spectrometer equipped with a high vacuum energy analyzer. With this method, surface of catalyst nanoparticles dispersed in liquid during catalysis at a relatively high temperature up to 150oC can be tracked with photoelectron spectroscopy. ______________________________________ *: To whom all correspondence should be addressed to. Email:
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1. Introduction One of the main functions of photoelectron spectroscopy are to determine the electronic states of the constituent atoms of a sample including oxidation state and electron transfer and to quantitatively analyze composition. In most cases, these studies of photoelectron spectroscopy are performed on the sample in environment of high vacuum (HV),
