A Study of the Optimal Conditions for the Development of Preferred Oriented Platinum Surfaces by Means of Fast Square Wave Potential Perturbations

Abstract

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.Recently, it was found that changes in the voltammetric response of polycrystalline platinum electrodes in the direction expected for preferred oriented surface electrodes can be achieved by using a fast repetitive square wave potential signal (RSWPS) within the potential range of H-and O-electroadsorption/electrodesorption in acid solution (1). Similar results were earlier obtained by applying a fast triangular potential signal to a polycrystalline platinum electrode in acid electrolyte at room temperature (2, 3). After applying the fast potential perturbation the electroae surface modifications were voltammetrically followed at a low potential sweep rate in the H-and O-electroadsorption/electrodesorption potential range by using an acid electrolyte. These changes in the electrode surface can also be seen through SEM for a relatively low magnification factor (4). The change from the initial polycrystalline platinum surface to the preferred oriented surface is independent of the shape of the periodic potential perturbation, but it is extremely sensitive to its frequency and potential limits (1, 2, 5). Thus, depending on the preset parameters of the potential perturbation either the platinum (100) preferred oriented surface or the platinum (111) preferred oriented surface are obtained (1-5).In the present work the influence of the RSWPS characteristics on the voltammetric response at low potential sweep rate of the resulting platinum surfaces is systematically studied to establish the optimal conditions for obtaining surface structures with a determined preferred orientation. ExperimentalRuns were made in 1M H2SO4 at 25~ with commercially available polycrystalline platinum wire shaped working electrodes of ca. 0.10 cm 2 geometric area. Previous to each experiment the working electrode was electropolished with ac (50 Hz; 10-15V) in a slightly acid (HC1) saturated CaC12 solution. Later, the electrode was repeatedly rinsed with triply distilled water and kept in water for lh before use. The potential of the working electrode was measured against a RHE in the acid electrolyte. A large area platinum counterelectrode (ca. 50 cm 2) concentrically surrounding the working electrode was used. The electrochemical cell and the instrumentation have been described elsewhere (1, 5). The distortion of the RSWPS, which was due to the proper risetime of the electrochemical setup, was less than 5% at frequencies lower than 6 kHz.After the pretreatment, the working electrode was subjected ...

Voltammetric stabilization of electrofaceted (100)-type platinum electrodes in acidic solutions

“…The voltammogram of the electrofaceted (100)-type Pt electrodes in 1 M &So4 in the 0.06-0.7 V range ( Fig. 1) reproduces exactly the one previously reported in the literature (1)(2)(3)(4) and is also very similar to the voltammogram of a Pt(100) single crystal electrode under the same conditions (12,(17)(18)(19)(20). The roughness factor of electrofaceted (100)-type Pt electrodes was 1.1 as determined by comparing the experimental H-adatom voltammetric charge density to that of the H-adatom monolayer calculated for a Pt(100) single crystal surface (15).…”

“…It has been recently found that the voltammetric characteristics of polycrystalline Pt can b e modified by applying fast potential cycling in acid electrolytes (1)(2)(3). Results obtained at present show that those electrodes exhibiting (100)-type preferred orientations behave in a very reproducible way and exhibit a very clear faceting (3)(4)(5). Nevertheless, the stabilized voltammetric response of these electrodes can be achieved only after they have been potential cycled under certain conditions within the potential range of bulk water stability.…”

“…The present work is devoted to study the stabilization of (100)-type preferred oriented Pt electrodes resulting after the electrochemical faceting treatment (1)(2)(3). The different stabilization stages are followed by conventional voltammetry and they depend on the potential cycling programme, electrolyte '~evision received March 23, 1988.…”

The Electrochemical Development of Pt(111) Stepped Surfaces and Its Influence on Methanol Electrooxidation

“…It has to be said that pc surfaces also exhibit surface restructuring, and in the case of the application of periodic potentials, they lead to the electroformation of microfacets [12]. It is well known that the application of fast potential periodic programs on platinum, rhodium, iridium, gold, or palladium produces permanent morphological changes with defined orientations, which depend on the potential limits and frequency of the routine by a microfacetting process [16][17][18]. The electrochemical responses of these stepped surfaces are similar to those of stepped crystalline surfaces [19,20].…”

Electrochemical Behavior and Semiempirical Approach to the Electroadsorption of 3-Buten-2-one and 2-Butanone on Platinum

“…The main characteristics of these potential programs are summarized in Ref. (14). On the other hand, it was recently found (20) that a potential program, consisting of a medium-frequency wave potential routine (MFWPR), applied to a Pt/aqueous acidic solution interface, produces H subsurface sites and the increase of (110) rows on the Pt surface.…”