Electrochemical faceting of single crystal platinum electrodes

The surface of a single crystal metallic sphere presents, in principle, all possible crystallographic planes. When such a surface structure is modified by one of the procedures described for the development of preferred orientation [ 1,2], one can develop a well defined atomic arrangement involving a certain particular crystallographic plane, depending on the set of parameters defining the fast potential perturbation. Due to the spherical geometry, the changes operating in the surface should require a very symmetrical stereospatial reconstruction, which results in the development of poles of the particular enhanced crystallographic plane and the disappearance of others.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Electrochemical faceting of single crystal platinum electrodes

The surface of a single crystal metallic sphere presents, in principle, all possible crystallographic planes. When such a surface structure is modified by one of the procedures described for the development of preferred orientation [ 1,2], one can develop a well defined atomic arrangement involving a certain particular crystallographic plane, depending on the set of parameters defining the fast potential perturbation. Due to the spherical geometry, the changes operating in the surface should require a very symmetrical stereospatial reconstruction, which results in the development of poles of the particular enhanced crystallographic plane and the disappearance of others.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Changes in real surface area, crystallographic orientation and morphology of platinum electrodes caused by periodic potential treatments: phenomenological approach

The changes in surface structure of polyfaceted single crystal platinum spheres subjected to repetitive square-wave potential treatments in acid solution have been studied . The dependence of the prevailing type of change on symmetry, potential limits and frequency of the periodic potential has been determined. Results are discussed on the basis of different reactions occurring within definite potential windows and distinct rate controlling processes depending on the operating conditions. Accordingly, the surface restructuring involves a predominant change in either the real surface area, the crystallographic orientation or the entire surface morphology.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

A study of the optimal conditions for the development of preferred oriented platinum surfaces by means of fast square wave potential perturbations

Changes in the voltammetric response of polycrystalline platinum in the direction expected for preferred oriented surface electrodes are achieved after applying a fast repetitive square wave potential signal covering the potential range of H‐ and O‐electroadsorption/electrodesorption. The influence of the characteristics of the square wave potential signal on the voltammetric response of the modified platinum surfaces is systematically studied to establish the optimal conditions for obtaining surface structures with determined preferred orientations.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Electrochemical faceting of metal electrodes

Electrochemical faceting is a term recently coined to denote the preferred crystallographic orientation of grains in polycrystalline metals developed when they are subjected to periodic potential perturbations of determined characteristics. Electrochemical faceting can also be applied to small single crystal beads resulting from melting polycrystalline metal wires. By properly adjusting the conditions defining the periodic perturbation, the resulting electrode surface acquires different preferred orientations which, depending on the nature of the electrode metal, can be followed either electrochemically through conventional voltammetry in the H and O electroadsorption/electrodesorption potential range, and in upd of different metals, or by scanning electron microscopy. The procedure has already been successfully applied to platinum, gold, rhodium and palladium. Electrochemical faceting involves at least two stages, namely, the initiation stage related to an electroadsorption process and a propagation stage associated with the electrodissolution and electrodeposition of the base metal in the acid electrolyte. Stabilization procedures for the freshly oriented surfaces and roughness development are also considered.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta

Electrochemical faceting of metal electrodes

Electrochemical faceting is a term recently coined to denote the preferred crystallographic orientation of grains in polycrystalline metals developed when they are subjected to periodic potential perturbations of determined characteristics. Electrochemical faceting can also be applied to small single crystal beads resulting from melting polycrystalline metal wires. By properly adjusting the conditions defining the periodic perturbation, the resulting electrode surface acquires different preferred orientations which, depending on the nature of the electrode metal, can be followed either electrochemically through conventional voltammetry in the H and O electroadsorption/electrodesorption potential range, and in upd of different metals, or by scanning electron microscopy. The procedure has already been successfully applied to platinum, gold, rhodium and palladium. Electrochemical faceting involves at least two stages, namely, the initiation stage related to an electroadsorption process and a propagation stage associated with the electrodissolution and electrodeposition of the base metal in the acid electrolyte. Stabilization procedures for the freshly oriented surfaces and roughness development are also considered.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta

Electrochemical faceting of single crystal platinum electrodes

The surface of a single crystal metallic sphere presents, in principle, all possible crystallographic planes. When such a surface structure is modified by one of the procedures described for the development of preferred orientation [ 1,2], one can develop a well defined atomic arrangement involving a certain particular crystallographic plane, depending on the set of parameters defining the fast potential perturbation. Due to the spherical geometry, the changes operating in the surface should require a very symmetrical stereospatial reconstruction, which results in the development of poles of the particular enhanced crystallographic plane and the disappearance of others.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Changes in the electrochemical response of polycrystalline platinum electrodes promoted by fast repetitive square wave potential signals

There is a great interest in modifying the properties of solid electrodes to achieve their best performance under definite operating conditions. In this sense, at present the preparation, stabilization and reproducibility in the electrochemical response of solid electrode surfaces are subjects of special attention. A recent contribution in this respect that polycrystalline platinum electrodes immersed in acid electrolytes after being subjected to a fast repetitive triangular potential scanning under carefully selected potential perturbation conditions show remarkable changes in the potentiodynamic I/E profiles at v = 0.1 V s -1 corresponding to the H- and O-adatom electroadsorption/ electrodesorption potential region with respect to those of the initial polycrystalline material. These results suggested that the same changes in the electrochemical response of platinum electrodes could be achieved by means of a fast repetitive square wave potential signal covering the potential range of the H- and O-adatom electroadsorption/electrodesorption.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

SEM micrography and voltammetric response of polyfaceted and electrochemically faceted single crystal rhodium electrodes

The electrochemical data reported in the literature on Rh electrodes is relatively scarce as compared to other noble metals such as Pt and Au[l-63]. Correspondingly, there are no unquestionable reference single crystal (SC) Rh systems available for establishing a direct correlation between the voltammetric response and the type of crystallographic face as for Pt and to some extent also for Au. [Extracto a modo de resumen]Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electroless copper deposition on a Pt polyfaceted single crystal

The present work is devoted to investigating electroless Cu deposition at regions neighbouring the Pt [100], Pt [110] and Pt [111] poles of polyfaceted microspherical Pt single crystals. The kinetics of this process are already known both in the presence and in the absence of additives in the plating bath.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada