Abstract
Metal-liquid interfaces are of the utmost importance in a number of scientific areas, including electrochemistry and catalysis. However, complicated analytical methods and sample preparation are usually required to study the interfacial phenomena. We propose an infrared spectroscopic approach that enables investigating the molecular interactions at the interface, but needing only minimal or no sample preparation. For this purpose, the internal reflection element (IRE) is wetted with a solution as first step. Second, a small plate of the metal of interest is put on top and pressed onto the IRE. The tiny amount of liquid that is remaining between the IRE and the metal is sufficient to produce an IR spectrum with good signal to noise ratio, from which information about molecular interactions, such as hydrogen bonding, can be deduced. Proof-of-concept experiments were carried out with aqueous salt and acid solutions and an aluminum plate.
Highlights
Interfaces between metals and fluids are omnipresent
We have shown that attenuated total reflection infrared (ATR-IR) spectroscopy is capable of analyzing the molecular interactions between solvent molecules and a metal surface
The solvent or a solution solution was initially placed on top of the ATR crystal, and, in the second step, a metal plate was was initially placed on top of the ATR crystal, and, in the second step, a metal plate was added and added and pressed onto the crystal
Summary
Interfaces between metals and fluids are omnipresent. Electrochemistry is the most obvious area, when an electrolyte is in contact with an electrode. Despite the importance of these systems, the analysis of the underlying physical and chemical phenomena is still a challenge This is true for those processes that are happening directly at the interface. E.g., when an electrochemical cell is under operation, an integral piece of information can be obtained by monitoring the electrical current and voltage, and/or by analyzing the bulk fluid at some distance to the surface. This allows for deducing information about the overall chemical oxidation and reduction reactions [7]. When the fluid (or some of its constituents) and the metal are not reacting, no information can be provided by measurements of current and bulk diagnostics
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