Strong Acid Electrolytes

Of greater industrial interest is the possibility of converting carbonyl compounds into the corresponding hydrocarbons. The reaction requires strongly acidic electrolytes. Examples of this reaction are syntheses in the areas of carotenoids 463) and fragrances 4641 ... 

The electrochemical reduction of imidazolecarboxylates gives a mixture (about 1 1) of ethers and alcohols when strongly acidic electrolytes are used 532) ... 

The electrochemical reduction of cyclic imides requires strongly acidic electrolytes, for example, a large excess of H2S04. This leads to large amounts of waste salts during the isolation of the reduction products ... 

There is a second group of metals like Fe, Cr, Ni and their alloys, which do not follow all predictions of their potential-pH diagrams. As an example, the Pourbaix Diagram for iron of Fig. 3 predicts corrosion for all potentials in strongly acidic electrolytes. However, experiments show that it is passive for potentials above a potential of Ep = 0.58 — 0.059 pH. For these conditions the passive layer is far from any dissolution equilibrium and its protecting properties have to be related to its slow dissolution kinetics. The same arguments hold for the passivation of Cr, Ni and their alloys. 

Chromium passivates very effectively down to very negative potentials even in strongly acidic electrolytes (Fig. 5). The cathodic current density of hydrogen evolution is followed by a small potential range of E = —0.4 to O V of anodic metal dissolution where Cr dissolves as Cr2+. At E > 0 V Cr passivates with a drop of the current density to less than 0.1 pA cm 2. In this potential range Cr3+ is the corrosion product. RRD studies have been applied to determine quantitatively the formation of Cr3+ ions. In principle the dissolution of Cr3+ at a Cr disc may be studied with two concentric analytical rings with their reduction to Cr2+ at the inner ring and its... 

Aliphatic carboxylic acids are reducible to the alcohol in low yield in strongly acidic electrolytes. Thus, phenylacetic acid is reduced to 2-phenylethanol in 25-50% yield at a lead cathode in 50% sulfuric acid-ethanol [39] and butyric acid to butanol in 80% sulfuric acid in 6.5% yield [40]. The latter conversion can also be performed in 17% yield in 7% aqueous sodium hydroxide, despite the fact that the carboxylate form of the acid, which is reducible only with difficulty, predominates in bulk solution, suggesting an electrocatalytic reduction involving specific interaction of the substrate and electrode surface. 

In macroscale electrolyses, lactams or fully saturated cyclic amines are obtained in good yields from imides in strongly acidic electrolytes [1-5] for example, 7V-methylsucci-nimide is reduced in good yield to A -methylpyrrolidone at a lead cathode in sulfuric acid solution [140]. 

The pseudocapacitance can also be provided by other pseudocapacitive materials such as some metal oxides and electrically conductive polymers (ECPs) that have much higher theoretical capacitance than carbon-based materials. These materials have been reviewed in detail elsewhere [89,90]. Although many materials have been reported to exhibit pseudocapacitive behavior, they are very sensitive to the type and pH of the electrolytes and few of them are suitable for application in strong acid electrolytes. As previously mentioned in Section 1.3.2, RUO2 is one of the most extensively studied pseudocapacitive materials in H2SO4 electrolytes. 

Formation of the alkane is believed to require a strongly acidic electrolyte and the highest yields have been obtained using lead, zinc, and zinc-amalgam cathodes/ t In contrast, low yields of the 1,2-diol (VIII) have been isolated... 

As a consequence of the strong interrelationship between PANI s optical properties and its redox chemistry, PANl possesses polyelectrochromic abilities. In strongly acidic electrolytes, PANl that is doped with small-molecule acids can stably and reversibly switch between its green ES and transparent LB forms at higher pH, PANI s ES state is dedoped to EB and the material s electroactivity is lost. Transitions from ES to the purple PB form of PANl involve the loss of protons and thus their electrochemistry is pH dependent. In the acidic media required to stabilize switching between ES and LB, however, the oxidation potential required to access PB is beyond the PANI s degradation... 

The polymer films characterized in a strong acidic electrolyte conq)osed of TEAP and perchloric acid in acetonitrile. 

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