Platinum electrodes deposition

Polymer films were produced by anodic deposition by potentiostatic deposition onto a platinum electrode. Deposition was done from 1 M solutions of the monomer in 1M LiC104 in acetonitrile. The films were characterized by cyclic voltammetry and reflection infrared spectroscopy in an apparatus described elsewhere [15]. 

C. Both the reduction and oxidation reactions can be catalyzed by porous platinum electrodes deposited on the zirconia ... 

Use and care of electrodes. Electrodes must be free from grease, otherwise an adherent deposit may not be obtained. For this reason an electrode should never be touched on the deposition surface with the fingers it should always be handled by the platinum connecting wire attached to the electrode. Platinum electrodes are easily rendered grease-free by heating them to redness in a flame. 

The existence of materials now included among the conducting polymers has long been known. The first electrochemical syntheses and their characterization as insoluble systems took place well over a century ago. In 1862 Letheby reported the anodic oxidation of aniline in a solution of diluted sulphuric acid, and that the blue-black, shiny powder deposited on a platinum electrode was insoluble in HjO, alcohol, and other organic solvents. Further experiments, including analytical studies, led Goppelsroeder to postulate in 1876 that oligomers were formed by the oxidation of aniline. 

As world deposits of petroleum and coal are exhausted, new sources of hydrogen will have to be developed for use as a fuel and in the production of ammonia for fertilizer. At present, most hydrogen gas is produced from hydrocarbons, but hydrogen gas can also be generated by the electrolysis of water. Figure 19-23 shows an electrolytic cell set up to decompose water. Two platinum electrodes are dipped in a dilute solution of sulfuric acid. The cell requires just one compartment because hydrogen and oxygen escape from the cell much more rapidly than they react with each other. 

Santos MC, Machado SAS (2004) Microgravimetric, rotating ring-disc and voltammetric studies of the underpotential deposition of selenium on polycrystalline platinum electrodes. J Electroanal Chem 567 203-210... 

The platinum electrode is also very convenient for investigating various adsorption phenomena in electrochemical systems. The surface of platinum is very stable and reproducible. As will be shown in what follows, the true working area can be determined with high accuracy for platinum surfaces with appreciable roughness and even for electrodes with highly dispersed platinum deposits. It is comparatively easy to clean the surface of adsorbed impurities and to control the state of the surface. 

Many elements of the p-block of the periodic table spontaneously adsorb on the surface of a platinum electrode when this is immersed in a solution containing a soluble salt of the element, without an external supply of electricity [Clavilier et al., 1988, 1989a, b, 1990a, b Evans and Attard, 1993 Feliu et al., 1988, 1991, 1993a, b Gomez et al., 1992 Sung et al., 1997, 1998]. The electrode can then be rinsed and transferred to an electrochemical cell that does not contain the corresponding ion of the deposited element, which remains on the surface, irreversibly adsorbed. 

Clavilier J, Feliu JM, Aldaz A. 1988. An irreversible structure sensitive adsorption step in bismuth underpotential deposition at platinum electrodes. J Electroanal Chem 243 419-433. 

More than a decade ago, Hamond and Winograd used XPS for the study of UPD Ag and Cu on polycrystalline platinum electrodes [11,12]. This study revealed a clear correlation between the amount of UPD metal on the electrode surface after emersion and in the electrolyte under controlled potential before emersion. Thereby, it was demonstrated that ex situ measurements on electrode surfaces provide relevant information about the electrochemical interface, (see Section 2.7). In view of the importance of UPD for electrocatalysis and metal deposition [132,133], knowledge of the oxidation state of the adatom in terms of chemical shifts, of the influence of the adatom on local work functions and knowledge of the distribution of electronic states in the valence band is highly desirable. The results of XPS and UPS studies on UPD metal layers will be discussed in the following chapter. Finally the poisoning effect of UPD on the H2 evolution reaction will be briefly mentioned. 

It is clear from the calculated limiting-current curves in Fig. 3a that the plateau of the copper deposition reaction at a moderate limiting-current level like 50 mA cm 2 is narrowed drastically by the surface overpotential. On the other hand, the surface overpotential is small for reduction of ferri-cyanide ion at a nickel or platinum electrode (Fig. 3b). At noble-metal electrodes in well-supported solutions, the exchange current density appears to be well above 0.5 A/cm2 (Tla, S20b, D6b, A3e). At various types of carbon, the exchange current density is appreciably smaller (Tla, S17a, S17b). 

Hiratsuka et al102 used water-soluble tetrasulfonated Co and Ni phthalocyanines (M-TSP) as homogeneous catalysts for C02 reduction to formic acid at an amalgamated platinum electrode. The current-potential and capacitance-potential curves showed that the reduction potential of C02 was reduced by ca. 0.2 to 0.4 V at 1 mA/cm2 in Clark-Lubs buffer solutions in the presence of catalysts compared to catalyst-free solutions. The authors suggested that a two-step mechanism for C02 reduction in which a C02-M-TSP complex was formed at ca. —0.8 V versus SCE, the first reduction wave of M-TSP, and then the reduction of C02-M-TSP took place at ca. -1.2 V versus SCE, the second reduction wave. Recently, metal phthalocyanines deposited on carbon electrodes have been used127 for electroreduction of C02 in aqueous solutions. The catalytic activity of the catalysts depended on the central metal ions and the relative order Co2+ > Ni2+ Fe2+ = Cu2+ > Cr3+, Sn2+ was obtained. On electrolysis at a potential between -1.2 and -1.4V (versus SCE), formic acid was the product with a current efficiency of ca. 60% in solutions of pH greater than 5, while at lower pH... 

The ellipsometer used in this study is described elsewhere(3). It consists of a Xenon light source, a monochromator, a polarizer, a sample holder, a rotating analyzer and a photomultiplier detector (Figure 1). An electrochemical cell with two windows is mounted at the center. The windows, being 120° apart, provide a 60° angle of incidence for the ellipsometer. A copper substrate and a platinum electrode function as anode and cathode respectively. Both are connected to a DC power supply. The system is automated with a personal computer to collect all experimental data during the deposition. Data analysis is carried out by a Fortran program run on a personal computer. 

A platinum disk electrode was electrolytically platinized in a platinum chloride solution to increase the surface area and enhance the adsorption power. The platinized platinum electrode was then immersed in a solution containing 10 mg ml l ADH. 0.75 mM and 6.2 mM NAD. After sufficient adsorption of these molecules on the electrode surface, the electrode was transferred into a solution containing 0.1 M pyrrole and 1 M KC1. Electrochemical polymerization of pyrrole was conducted at +0.7 V vs. Ag/AgCl. The electrolysis was stopped at a total charge of 1 C cm 2. An enzyme-entrapped polypyrrole membrane was deposited on the electrode surface. 

More recently, electrochemical oligomerization of hydrosilanes has been demonstrated.130,131 A DME/TBAF solvent/electrolyte system with platinum electrodes was found to lead successfully to products 31, according to the reaction in Scheme 18, after use of a THF/LP system had led to deposition of lithium. 

In this type of DSSCs, once the dye is photoexcited, charge separation drives electrons from the valence band (vb) of the semiconductor to the photoexcited dye. Common to both types of DSSCs is the regeneration of the oxidized or reduced dye by a redox mediating electrolyte. The latter is mainly in the form of a liquid and/or a solid. Platinum films deposited onto ITO or FTO are the most utilized counter-electrodes and are required to close the electronic circuit. 

Platinum chemically deposited on a Nafion membrane was used as a platinum SPE (Solid Polymer Electrolyte) electrode. The electrochemical measurements were performed using the half cell shown in Fig. 2-2. The cell body is made from Teflon (PTFE). The cell is divided into two compartments one for backside gas supply one for the electrolyte. SPE electrodes are placed between them with the deposited side facing the gas compartment. A gold foil with a hole was placed behind the SPE electrode... 

The cel used for formation of SPE electrodes is shown in Fig. 2-12. To make a tight contact between the membrane and platiniun layer, small amount of platinum partides were deposited as nudei. Then a thick layer of platinum was deposited. This is a new way to fabricate a SPE electrode. 

Aramata et al. applied this electroless deposited platinum electrode for methanol oxidation for the first time in 1983. They issued a series of reports on this subject.They are summarized as follows ... 

Tin was electrochemically deposited on smooth and high area (chemically platinized) platinum electrodes at -300 mV for 10 s. The thermodynamic potentials for tin metal and its ions are ... 

The temperature sensor in the membrane center is made of polysilicon with a nominal resistance of 10 kQ. An additional reference resistor is needed for the control circuitry (Sect. 5.1). For the resistance measurement of the sensitive layer, platinum electrodes are deposited on top of the CMOS aluminum metallization in order to establish good electrical contact to the sensitive metal oxide. 

Besides silicon, other materials have also been used in micro fuel cells. Cha et al. [79] made micro-FF channels on SU8 sheets—a photosensitive polymer that is flexible, easy to fabricate, thin, and cheaper than silicon wafers. On top of fhe flow channels, for both the anode and cathode, a paste of carbon black and PTFE is deposited in order to form the actual diffusion layers of the fuel cell. Mifrovski, Elliott, and Nuzzo [80] used a gas-permeable elastomer, such as poly(dimethylsiloxane) (PDMS), as a diffusion layer (with platinum electrodes embedded in it) for liquid-electrolyte-based micro-PEM fuel cells. 

Tetraphenylarsonium pertechnetate is precipitated in the presence of perchlorate as the carrier. The mixed salts are disolved in concentrated sulfuric acid and the solution is electrolyzed at platinum electrodes. The black deposit (TcOj) obtained is dissolved in perchloric acid, technetium heptoxide is distilled out of the solution... 

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