Borohydride, redox potential

Sodium dithionite is well established [ 1 ] as a powerful reducing agent under alkaline conditions. Its redox potential is close to that of sodium borohydride [2] and, in several respects, there are advantages in the use of sodium dithionite as an alternative to the metal hydrides under phase-transfer catalytic conditions, particularly in the reduction of carbonyl compounds [3],... 

For the preparing of nanodispersed electrocatalysts which are composed of two, three or even more elements, the procedure of Bonnemann became very popular. This preparation method produces a well-defined molecular mixture and where possible well-defined alloys of the elements in the electrocatalyst particles of nanometer size. It is essentially based on reductive precipitation of metals from their salt solutions in aprotic media by a borohydride, a very strong reductant. The objective is the forced co-deposition of metals irrespective of their redox potential or different degree of nobility. 

Borohydride Hydrides have attracted considerable interest as a fuel for use in DLFCs due to their high energy density and low redox potential. Borohydride (BH4-) is a possible candidate for practical application because of its stability in basic aqueous solution. The ideal electrochemical oxidation of BH4 is an eight-electron reaction, as shown in Eq. (6.14),... 

The redox potential in Eq. (6.14) is -0.4 V versus a reversible hydrogen electrode (RHE). Although BH4 is more resistant to hydrolysis than other hydrides such as alanates, the hydrolysis of BHa" (Eq. (6.15)) readily occurs in the presence of some catalysts. In particular, platinum-based catalysts, which are common anodes in direct borohydride fuel cells (DBFCs), cause significant decomposition of BH4". 

For the preparation of the silver samples, hydrogen, borohydride, formaldehyde, hydrazine are usually used as reducers. One of the conditions preventing silver crystallites from growing, is a high rate of reduction of Ag+ cations. As a rule, the higher the rate of reduction, the higher the value of the redox potential of the reducer. 

In contrast to standard borohydride reductive nanoparticle synthesis, we have developed an alternative strategy to amino acid encapsulated nanoparticles by utilizing a metal nanoparticle (M°-(Ligand))/metal ion (M"+) precursor redox pair with matched oxidation/reduction potentials. Simply, a metal nanoparticle such as Pt°-(Cys) acts as the principal reductant to a complimentary selected metal ion of Au + resulting in a new stabilized metal nanoparticle of Au°-(Cys) and the oxidation product of the original nanoparticle Pt"+. Malow et al. have reported a metathesis/transmetallation type reaction between a platinum colloid and a Au cyanide compound. Similarly, we employed a Pt°-(Cys)/AuCl4 pair and 0.5-2.0 equivalents of Au to Pt -(Cys). XRD analysis of the nanoparticle products revealed differences in crystallinity... 

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