Electrochemical Study of Bi[sub 2]O[sub 3] and Bi[sub 2]O[sub 2]CO[sub 3] by Means of a Cavity Microelectrode. I. Observed Phenomena and Direct Analysis of Results

Abstract

Bi element is included within various complex oxides, in high transition-temperature superconductors BiSrCaCuO, or in manganese dioxide as in rechargeable battery material, for example. [1][2][3][4][5][6][7][8][9][10][11][12] It more or less modifies the properties of the material. For instance, the various species of Mn(IV) oxides are rechargeable when the deep discharge is lower than 0.5 faradays (Ᏺ) per Mn atom, [13][14][15][16][17][18] but when Bi atoms are included, they become electrochemically reversible for deep discharge higher than 1.5 Ᏺ/Mn. [4][5][6][7][8][9][10][11][12] It is interesting to know the interaction between Bi atoms and the metal atom of the matrix host through the eventual modifications of the redox potential. In order to have references for comparison, Bi 2 O 3 and its derivatives have been studied using the usual composite electrodes, also called graphite or carbon paste electrodes. 19,20 These electrode devices do not allow scanning at a rate higher than a few millivolts per second. Therefore, it is not possible to determine the kinetic features of the electrochemical processes. The cavity microelectrode (CME) has been recently invented for studying a very small amount of powder material (10 Ϫ7 to 10 Ϫ8 g). 21,22 It allows for reaching scan rates up to a few tens of volts per seconds. 23,24 This paper is devoted to both the description and direct analysis of results obtained for Bi 2 O 3 and Bi 2 O 2 CO 3 by means of the CME. ExperimentalMaterial and physicochemical characterization.-Bi 2 O 3 is obtained by precipitation of 1 M Bi(NO 3 ) 3 solution in 1 M KOH at room temperature. The solid is filtered, washed with distilled water, and dried at 80ЊC. It is stored at room temperature in a closed bottle. After a storage of several years, the product is fully carbonated giving Bi 2 O 2 CO 3 as determined by elemental analysis and by X-ray diffraction (XRD). A specific area is measured by means of a device from Coulter, type SA3100.CME and optical control devices.-The CME (Fig. 1a) is made of a glass tube (diam glass : 5 to 6 mm, total length, ᐉ tot : 80 to 150 mm) containing a Pt wire (diam pt : 25 to 50 m, length 3 cm) which ends near the bottom of the glass tube thus providing a cylindrical cavity (Fig. 1b). This cavity is obtained by controlled dissolution of the platinum wire in a highly concentrated HCl ϩ HNO 3 solution. The connection between the Pt wire and the copper wire col-lector is achieved by embedding the end of the two wires in graphite powder. The diameter pt and the deepness h c of the microcavity is measured by a microscope (Olympus BX30

Composition and electrochemical properties of natural patinas of outdoor bronze monuments

“…The cavity microelectrode consisted in a platinum microelectrode (60 m in diameter) sealed in a large-glass tube (8 mm in diameter) [17,18]. A small cylindrical cavity (60 m in diameter and 25 m in depth) was obtained by a laser ablation of the platinum wire.…”

“…First, the electrochemical process taking place at the substrate|electrolyte interface was discarded; second, a thin powder layer allowed the minimization of the indepth distribution of both potential and current, and finally, only a small amount of patina is needed. The volume of the cavity used is 50 × 10 −9 cm 3 [18]. With the density of patina in the cavity estimated to 2.5, the mass necessary will be 125 ng to perform experiments.…”

Metal plating via electrochemical reduction of oxide layers formed by electrophoretic deposition

“…10), 11) On the basis of the present experimental results, it can be concluded that dense Zn or Bi layers can be successfully fabricated using a combined technique of common electrophoretic deposition of oxide particles and electrochemical reduction. The overall process is performed in environmentally benign aqueous solutions with a neutral pH range.…”

Methanol Tolerant Oxygen Reduction Catalysts Derived from Electrochemically Pre‐treated Bi2Pt2–yIryO7 Pyrochlores

“…The leaning of the CVs is caused by the porosity of the home-made powder pellet [13]. In order to investigate the reductive activation process in more detail, very small amounts of pyrochlore powders were [14] or PtO x /Ti electrodes [15], and have been assigned to the formation of Bi metal and Pt metal, respectively. The dashed curve in Figure 2 was recorded immediately after completion of the first CV scan and its shape closely resembles CVs recorded by Wilde and Zhang [16] for Pt electrodes immersed into perchloric acid solutions containing dissolved Bi III species.…”