In previous research completed by Iski et al. and Itaya et al, it was found that through specific electrochemical methods, a silver (Ag) monolayer could be formed on a Au(111) surface in a chloride-rich or chloride-free solution. The electrochemical method used was under potential deposition (UPD) which formed a monolayer from either AgCl or AgClO4, respectively. In the previous studies, one specific UPD peak was investigated. Through a detailed electrochemical study, we have found that the UPD of Ag on a Au(111) surface can occur at two different underpotentials, one resulting from the reduction of Ag+ to the surface and the other resulting from the reduction of a solvated silver halide unit (AgX) to the surface. Furthermore, we have determined that, depending on the potential supplied to the system, the layer formed at the surface can either be thermally stable or unstable up to 1,000 K. The atomic structure of these films can be studied with electrochemical scanning tunneling microscopy (EC-STM), which not only allows for atomic-scale imaging of the surface layer within an electrochemical environment, but also facilitates the taking of cyclic voltammograms (CVs), which can be used to examine the redox behavior of the systems. Through this electrochemical manipulation, the reduction of Ag+ to the surface can be investigated in multiple silver halide systems and the thermal stability investigated. Despite many studies on these types of surface layers, very few publications have directly studied the thermal stability of the UPD of Ag on Au(111) using varied silver halide sources. Through STM imaging, the newly modified surface can be imaged and the structure of the Ag monolayer investigated under a liquid layer while holding a constant potential. STM evidence shows that the amount of Ag on the surface is the same regardless of the Ag source used but does change based on application potential. Furthermore, electrochemical studies into these Ag monolayers have led to a better understanding of the properties of these surfaces and the exact nature of the redox chemistry occurring at the relevant potential. Using EC-STM, studies were conducted on how different UPD depositions affect the thermal stability of the system.

Electrochemical control of the thermal stability of atomically thin Ag films on Au(111)

2019 Spring National Meeting

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