Acids as electrolytes

The use of methane sulfonic acid as electrolyte eliminates the slurry electrolyte, allows higher Ce4+ concentrations up to 1 M and simplifies process-design... 

As the state-of-the-art PEMFC electrodes are optimized for operation below 100 °C and the use of perfluorosulfonic acid as electrolyte, significant new R D will be needed when a new electrolyte emerges with high temperature operation as a consequence. 

Carvalho has studied the separation of technetium from rhenium by electrophoresis and paper chromatography. Good separations can be obtained by electrophoresis using either alkaline hydra2dne sulfate or a solution of SnClj in hydrochloric acid as electrolytes. Both elements can sufficiently be separated by paper... 

Smooth platinum, lead dioxide and graphite are anode materials commonly used in electrooxidation processes. All show large overpotentials for oxygen evolution in aqueous solution. Platinum coated titanium is available as an alternative to sheet platinum metal. Stable surfaces of lead dioxide are prepared by electrolytic oxidation of sheet lead in dilute sulphuric acid and can be used in the presence of sulphuric acid as electrolyte. Lead dioxide may also be electroplated onto titanium anodes from lead(Il) nitrate solution to form a non-porous layer which can then be used in other electrolyte solutions [21],... 

Early electrochemical processes for the oxidation of alcohols to ketones or carboxylic acids used platinum or lead dioxide anodes, usually with dilute sulphuric acid as electrolyte. A divided cell is only necessary in the oxidation of primary alcohols to carboxylic acids if (he substrate possesses an unsaturated function, which could be reduced at the cathode [1,2]. Lead dioxide is the better anode material and satisfactory yields of the carboxylic acid have been obtained from oxidation of primary alcohols up to hexanol [3]. Aldehydes are intermediates in these reactions. Volatile aldehydes can be removed from the electrochemical cell in a... 

Nitroguanidine is reduced to aminoguanidine 24 in good yields using aqueous sulphuric acid as electrolyte when the product precipitates as the hydrogen sulphate [124,125], Nitrourea affords semicarbazide on reduction in acid solution [126]... 

Phosphoric acid fuel cell (PAFC) working at 180-200 °C vfith a porous matrix of PTFE-bonded silicon carbide impregnated with phosphoric acid as electrolyte, conducting by the H cation. This medium-temperature fuel cell is now commercialized by ONSI (USA), mainly for stationary applications. 

FIGURE 13.19 CE/ESI-MS electropherogram for the analysis of three selenium species (SeM, SeC, and SeCM) using 5% acetic acid as electrolyte buffer. The insets give information about the isotopic patterns of the species. (Reprinted from Michalke et al. 1999 Fresenius J. Anal. Chem. 363 456-459.)... 

Intermolecular reaction between acetone and an alkene was first carried out only in low yields using acetone as the solvent and either / -toluenesulfonic acid or sulfuric acid as electrolyte [44-46]. Conjugated alkenes reduced at less negative potentials than acetone... 

Alkylthioacetonitriles when oxidized anodically in methanol and /7-toluenesulfonic acid as electrolyte produce a-methoxylated sulfides [104]. Their formation is tentatively explained by a Pummerer-type intermediate in which the presence of the cyano group appears to facilitate deprotonation at the a-position ... 

The Standard Potential of Chlorine. Measurements of the potentials of galvanic cells without liquid junctions from which the standard potential of chlorine may be deduced have been made by Lewis and Ruppert40 who used, as one electrode, platinum over which a mixture of chlorine and nitrogen was bubbled, and, as reference, a calomel electrode and hydrochloric acid as electrolyte. The arrangement may be represented by... 

The electrolyte also plays an important role in the cell performance. For the propane oxidation in a fuel cell the monohydrate of trifluoromethanesulfonic acid as electrolyte had, at a platinum electrode at 135 °C, a limiting current which was more than 1000% greater than that of phosphoric acid . ... 

Covering layers are often formed on the electrodes in such polymerizations, which, of course, is undesirable in terms of polymer recovery. On the other hand, this effect can be utilized to form covering layers on metals. But only certain monomer-electrode combinations can be used for this purpose. For example, steel is suitable for acrylonitrile or vinyl acetate, whereas zinc, lead, and tin can be used with / -xylylene or diacetone acrylamide, CH3COCH2—C(CH3)2—NH—OC—CH=CH2, using dilute sulfuric acid as electrolyte in each case. 

A. Goni-Urtiaga, D. Presvytes, K. Scott, Sohd acids as electrolyte materials for proton exchange membrane (PEM) electrolysis review, Int. J. Hydrogen Energy 37 (2012) 3358-3372. 

In contrast to P E FCs, the elevated operating temperature leads to different cooling strategies. The use of phosphoric acid as electrolyte permits operating temperatures up to 220 °C, whereas the typical operating temperature of an HT-PEEC is about 160 °C. This excludes liquid water as a cooling medium at ambient pressure, hence stacks are cooled with either air or oil. 

The redox potentials of the various peaks of the polyaniline (PAn) in different organic acids as electrolyte are given in Table 12.11. 

As an outlook to further improvements of catalyst kinetics and durability in low-and high-temperature polymer electrolyte fuel cells, several possibilities are currently under investigation [73] (1) extended large-scale Pt and Pt-alloy surfaces [70] (2) extended nanostructured Pt and Pt-aUoy films [74] (3) de-alloyed Pt-alloy nanoparticles [75] (4) precious metal free catalyst as described by Lefevre et al. [76], e.g., Fe/N/C catalysts and (5) additives to the electrolyte which modify both adsorption properties of anions and spectator species and also the solubility of oxygen [77]. The latter approach is specific to fuel cells using phosphoric acid as electrolyte. 

During the electrolytic step of copper production an anode slime is obtained, containing the noble metals of the ore. They are extracted by a compHcated process. Raw silver is obtained by melting, and is used as a new anode material. In an electrolytic process with nitric acid as electrolyte silver dissolves from the anode while gold and platinum form a new anode sHme. Silver is precipitated from the electrolyte as silver chloride. This is melted with soda and saltpeter at 1000°C. The molten silver is cast into bars and remelted in vacuum to yield very pure, gas-free silver. 

One of the most popular cells in the beginning of the 19th century was the so-called Grove element with nitric acid as electrolyte. Bunsen improved the Grove element by introducing a carbon rod instead of a platinum rod (1841). 

---