Applications of surface analysis techniques to the study of electrochemical systems.

摘要

The electrochemical properties of carbon films prepared by catalytic chemical vapor deposition on clean Ni(111), using an equimolar CO:CH 4 mixture at a total pressure ca. 2 x 10-5 kPa (1.5 x 10-4 Torr) as the carbon source, have been examined under ultrahigh vacuum (UHV) conditions (6.7 x 10 -11 kPa) in pre-electrolyzed LiClO4-poly(ethylene)oxide (PEO) solutions (1 Li+:36 ethylene oxide units) at ca. 55°C. All steps involved, including carbon film preparation, electrochemical cell assembly and electrolyte prelectrolysis were carried out in the same UHV chamber under highly controlled conditions without exposure to the ambient atmosphere.; The electrochemistry of glassy carbon electrodes prepared and characterized in UHV was observed in a non-aqueous electrolyte, 1M LiPF6 in Diethyl Carbonate: Ethyl Methyl Carbonate (DEC:EMC). This combination of ex-situ spectroscopic and electrochemical characterization techniques was achieved by the construction of a custom built ultrahigh vacuum (UHV) compatible system, which allows in-situ ultra-purification and mass spectrometric analysis of electrolytes. In addition, it enables electrochemical testing of carbon electrodes cleaned and characterized in a separate UHV chamber, equipped with an array of surface preparative and spectroscopic techniques. Specimens were transferred between the two chambers using a UHV compatible portable chamber, making it possible to perform surface characterization before and after electrochemical experiments with X-ray photoelectron spectroscopy (XPS).; Electrodeposition of Al from McEtimCl/AlCl3 onto a metal substrate characterized using AES in ultrahigh vacuum was achieved in a redesigned UHV system and an independently pumped liquid handling/introduction chamber. The room temperature molten salt used (MeEtimCl/AlCl3) is a moisture sensitive salt that has been used as an Al plating bath solution for decades. Coupling the room temperature molten salt with UHV produces a unique liquid electrolyte based UHV electrochemical system. The advantage of this approach is that electrodeposition under potential control can be observed and recorded on surfaces cleaned and characterized in UHV. There are a wide range of metals and alloys that are known to electrodeposit and codeposit from this electrolyte which can used to probe electrochemical phase formation and growth under these conditions.