Alkaline electrolytes

Flartinger S, Pettinger B and Dobihofer K 1995 Cathodic formation of a hydroxyl adsorbate on copper (111) electrodes in alkaline electrolyte J. Electroanal. Chem. 397 335-8... 

Alkaline Fuel Cell. The electrolyte ia the alkaline fuel cell is concentrated (85 wt %) KOH ia fuel cells that operate at high (- 250° C) temperature, or less concentrated (35—50 wt %) KOH for lower (<120° C) temperature operation. The electrolyte is retained ia a matrix of asbestos (qv) or other metal oxide, and a wide range of electrocatalysts can be used, eg, Ni, Ag, metal oxides, spiaels, and noble metals. Oxygen reduction kinetics are more rapid ia alkaline electrolytes than ia acid electrolytes, and the use of non-noble metal electrocatalysts ia AFCs is feasible. However, a significant disadvantage of AFCs is that alkaline electrolytes, ie, NaOH, KOH, do not reject CO2. Consequentiy, as of this writing, AFCs are restricted to specialized apphcations where C02-free H2 and O2 are utilized. 

The Huron-Dow Process. The Huron-Dow (H-D) process is a refinement of the cathodic reduction of oxygen in an alkaline electrolyte yielding low strength hydrogen peroxide directiy. Earlier attempts reHed on neutralizing the excess caustic or forming insoluble metal peroxides (92). The two reactions involved are... 

Cylindrical alkaline cells are 2inc—manganese dioxide cells having an alkaline electrolyte, which are constmcted in the standard cylindrical si2es, R20 "D", R14 "C", R6 "AA", R03 "AAA", as well as a few other less common si2es. They can be used in the same types of devices as ordinary Leclanchn and 2inc chloride cells. Moreover, the high level of performance makes them ideally suited for appHcations such as toys, audio devices, and cameras. 

However, the reaction with water can be made to be extremely slow. Because the alkaline electrolyte is corrosive toward human tissue as well as toward the materials ia devices, it is more important to have a good seal toward preventing electrolyte leakage ia an alkaline battery than ia a carbon—2iac cell. The formation of a good seal is, however, iacompatible with the formation of a noncondensable gas like hydrogen. 

Discharging to this lower cell voltage usually results ia shorter cycle life. Enough excess iron should be provided ia the cell design to avoid this problem. Active iron ia the metallic state is slowly attacked by the alkaline electrolyte according to... 

Lithium as an anode in alkaline electrolyte has been considered in the battery system shown in Figure 29. Even though lithium reacts dkecdy with water, it was possible to operate the battery because of a protective lithium hydroxide film that forms on the anode. However, the film was not totally protective and units exhibited poor efficiency and were very complex. 

The enamel mill addition, degree of firing and furnace atmosphere all affect acid resistance. An increase in clay and alkaline electrolyte detracts from this property and underfiring also has an adverse effect. The use of organic suspending agents is thus preferable to clays, from this aspect, but... 

It is so universally applied that it may be found in combination with metal oxide cathodes (e.g., HgO, AgO, NiOOH, Mn02), with catalytically active oxygen electrodes, and with inert cathodes using aqueous halide or ferricyanide solutions as active materials ("zinc-flow" or "redox" batteries). The cell (battery) sizes vary from small button cells for hearing aids or watches up to kilowatt-hour modules for electric vehicles (electrotraction). Primary and storage batteries exist in all categories except that of flow-batteries, where only storage types are found. Acidic, neutral, and alkaline electrolytes are used as well. The (simplified) half-cell reaction for the zinc electrode is the same in all electrolytes ... 

Despite the fact that the zinc/ ferricyanide system employs an alkaline electrolyte, the electrode reactions are quite similar to those in zinc/halogen batteries and battery constructions are usually bipolar too. 

Several significant electrode potentials of interest in aqueous batteries are listed in Table 2 these include the oxidation of carbon, and oxygen evolution/reduction reactions in acid and alkaline electrolytes. For example, for the oxidation of carbon in alkaline electrolyte, E° at 25 °C is -0.780 V vs. SHE or -0.682 V (vs. Hg/HgO reference electrode) in 0.1 molL IC0 2 at pH [14]. Based on the standard potentials for carbon in aqueous electrolytes, it is thermodynamically stable in water and other aqueous solutions at a pH less than about 13, provided no oxidizing agents are present. 

In acid electrolytes, carbon is a poor electrocatalyst for oxygen evolution at potentials where carbon corrosion occurs. However, in alkaline electrolytes carbon is sufficiently electrocatalytically active for oxygen evolution to occur simultaneously with carbon corrosion at potentials corresponding to charge conditions for a bifunctional air electrode in metal/air batteries. In this situation, oxygen evolution is the dominant anodic reaction, thus complicating the measurement of carbon corrosion. Ross and co-workers [30] developed experimental techniques to overcome this difficulty. Their results with acetylene black in 30 wt% KOH showed that substantial amounts of CO in addition to C02 (carbonate species) and 02, are... 

The major oxidation reactions of acetylene black in an alkaline electrolyte (30 wt% KOH + 2 wt% LiOH) are strongly dependent on the potential (vs. Hg/HgO) and temperature [30] ... 

Other experiments by Ross and co-workers [30] clearly indicate that the common metal (Co, Ni, Fe, Cr, Ru) oxides that are used for oxygen electrocatalysts also catalyze the oxidation of carbon in alkaline electrolytes. 

The surface structure has a strong influence on the corrosion rate of carbon in both acid and alkaline electrolytes. Studies by Kinoshita [33] clearly showed that the specific corrosion rate mAcm"2 of carbon black in 96 wt% H3P04 at 160 °C was affected by heat treatment. A similar trend in the corrosion rate in alkaline electrolyte was observed by Ross [30c], as shown in Fig. 4. It is evident that the corrosion rates of the nongraphitized carbons are higher than those of the corresponding graphitized carbons. Their study further indicated that some types of carbon blacks (e.g., semi... 

Carbon shows reasonable electrocatalytic activity for oxygen reduction in alkaline electrolytes, but it is a relatively poor oxygen electrocatalyst in acid electrolytes. A detailed discussion on the mechanism of... 

The reason for this limited cycle life is the high solubility of the zinc electrode in alkaline electrolyte the zincate ions formed are deposited again during the subsequent charging in the form of dendrites, i.e., of fernlike crystals. They grow in the direction of the counterelectrode and finally cause shorts. 

Figure 17. PMC behavior in the accumulation region, (a) PMC potential curve and photocurrent-potential curve (dashed line) for silicon (dotted with Pt particles) in contact with propylene carbonate electrolyte containing ferrocene.21 (b) PMC potential curve and photocurrent-potential curve (dashed line) for a sputtered ZnO layer [resistivity 1,5 x 103 ft cm, on conducting glass (ITO)] in contact with an alkaline electrolyte (NaOH, pH = 12), measured against a saturated calomel electrode.22...

The hydrogen-oxygen cell used in the space shuttle is called an alkali fuel cell, because it has an alkaline electrolyte ... 

Kutzmutz St, Lang G, Heusler KE (2001) The electrodeposition of CdSe from alkaline electrolytes. Electrochim Acta 47 955-965... 

Tittes K, Plieth W (2007) Electrochemical deposition of ternary and binary systems from an alkaline electrolyte—a demanding way for manufacturing p-doped bismuth and antimony teUurides for the use in thermoelectric elements. J Solid State Electrochem 11 155-164... 

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