Single crystal electrode surface preparation

Preparation of the Pt(lll) Single-Crystal Electrode. The Pt single-crystal electrode was prepared according to the procedure developed by Clavilier (7) and oriented using the methodology of Hamelin (8). It was subsequently polished with alumina to a mirror-like finish. The quahty of the Pt(l 11) surface was verified by recording CV... 

The chemisorption of species occurs at specific sites on the electrode, for example on top of certain atoms, or in the bridge position between two atoms. Therefore, most adsorption studies are performed on well-defined surfaces, which means either on the surface of a liquid electrode or on a particular surface plane of a single crystal. Only fairly recently have electrochemists learned to prepare clean single crystal electrode surfaces, and much of the older work was done on mercury or on amalgams. 

Adsorption of acetic acid on Pt(lll) surface was studied the surface concentration data were correlated with voltammetric profiles of the Pt(lll) electrode in perchloric acid electrolyte containing 0.5 mM of CHoCOOH. It is concluded that acetic acid adsorption is associative and occurs without a significant charge transfer across the interface. Instead, the recorded currents are due to adsorption/desorption processes of hydrogen, processes which are much better resolved on Pt(lll) than on polycrystalline platinum. A classification of adsorption processes on catalytic electrodes and atmospheric methods of preparation of single crystal electrodes are discussed. 

Underpotential deposition is described as less than monolayer metal deposition on a foreign metal substrate, which occurs at more positive potentials than the equilibrium potential of a metal ion deposed on its own metal, expressed by the Nemst equation. Kolb reviewed state-of-the-art Underpotential deposition up to 1978. As Underpotential deposition is a process indicative of less than a monolayer metal on a substrate, it is expected to be quite sensitive to the surface stmcture of the substrate crystal a well-defined single-crystal electrode preparation is a prerequisite to the study of Underpotential deposition. In the case of Au and Ag single-crystal electrodes, Hamelin and co-workers extensively studied the necessary crystal surface structure, as reviewed in Ref. 2. 

Reduction of N2O was used as model electrocatalytic reaction on well-defined surfaces [102, 103]. Pt(lll) and Pt(lOO) electrodes covered with Rh adlayers were prepared for these studies. It was shown that the adsorptive and catalytic activity of the adlayers differs from those of the bulk single-crystal electrodes. 

Preparation As compared to single-crystal Ag surfaces, the preparation of pc-Ag electrode may seem to be a relatively simple task. However, a pc-Ag surface, which ensures reproducibility and stabiKty, also requires a special procedure. Ardizzone et al. [2] have described a method for the preparation of highly controlled pc-Ag electrode surface (characterized by electrochemical techniques and scanning electron microscopy (SEM)). Such electrodes, oriented toward elec-trocatalytic properties, were successfully tested in hahde adsorption experiments, using parallelly, single-crystal and conventional pc-Ag rods as references. 

Surface Electrochemistry is an important field in Surface Science, which is undergoing a very important development. In spite of the complexity of the systems, the experimental measurements have acquired a very high degree of sophistication and atomic resolution has almost been reached. After the development of special techniques that allowed the preparation of well defined single crystal electrodes [1, 2], attempts have been made to use surface analysis techniques in an electrochemical environment. However, one must... 

A different approach to the preparation of preferentially oriented surfaces on polycrystalline systems has been demonstrated by Sumino and Shibata. In References 57-59 it has been shown that a fast-cycling treatment is not required for obtaining deposits with preferential orientation. A platinum electrode with a single-crystal (100) surface was obtained by annealing a thin platinum film electrodeposited on a polycrystalline platinum foil. 

The surface electrochemistry of Pt single-crystal electrodes has been exhaustively studied using cyclic voltammetry [5, 8-12, 61-67]. Phenomena of a step reconstruction and step coalescence have been observed [61]. For Pt(lll)-H20 interface, prepared by the flame annealing method, a double-layer charging has been observed only in a very narrow potential region (0.1 < E < 0.35 V (SCE) in 0.05 M H2SO4), which depends on the chemical... 

Electrochemical atomic layer epitaxy (EC-ALE) is the combination of underpotential deposition (UPD) and ALE. UPD is the formation of an atomic layer of one element on a second element at a potential under, or prior to, that needed to deposit the element on itself [5, 6]. The shift in potential results from the free energy of the surface compound formation. Early UPD studies were carried out mostly on polycrystalline electrode surfaces [7], This was due, at least in part, to the difficulty of preparing and maintaining single-crystal electrodes under well-defined conditions of surface structure and cleanliness [8]. The definition of epitaxy is variable but focuses on the formation of single crystal films on single crystal substrates. This is different from other thin film deposition methods where polyciystalline or amorphous film deposits are formed even on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element and is much... 

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