Potentiostatic synthesis

Prakasam HE, Varghese OK, Paulose M, Mor GK, Grimes CA (2006) Synthesis and photoelectrochemical properties of nanoporous Iron (III) oxide by potentiostatic anodization. Nanotechnology 17 4285-4291... 

One of the most important, yet latent, applications of controlled-potential electrolysis is electrochemical synthesis. Although electrolysis has been used for more than a century to synthesize various metals from their salts, application to other types of chemical synthesis has been extremely limited. Before the advent of controlled-potential methods, the selectivity possible by classical electrolysis precluded fine control of the products. The only control was provided by appropriate selection of electrode material, solution acidity, and supporting electrolyte. By these means the effective electrode potential could be limited to minimize the electrolysis of the supporting electrolyte or the solvent. Today potentiostats and related controlled-potential-electrolysis instrumentation are commercially available that provide effective control of the potential of the working electrode to 1 mV, and a driving force of up to 100 V for currents of up to several amperes. Through such instrumentation electrochemical syn-... 

Apparatus and materials. All electrochemical polymerizations, amperometric measurements and cyclic voltammetry were carried out with an EG G Princeton Applied Research Potentiostat model 273. Pyrrole was purified by vacuum distillation and by passage over neutral alumina prior to electropolymerization. The polyanions (1) used as dopants are shown in Figure 1, and were purified twice by precipitation from methanol in 0.1 M HC1. Detailed information about their synthesis and catalytic... 

It is much easier to produce the correct energy level for the receipt of electrons from a reactant into the electrode in an anodic synthesis than to arrange for effective electron transfer in a homogeneous solution. In the electrochemical method, one calmly adjusts the potentiostat setting in a solution that may be near room temperature. In solution, one has to worry about adjusting reactants and products—probably catalysts—until it works. And it may be that the chemical reaction won t work at a significant rate until the temperature is raised. 

Electrolyses at sacrificial electrodes allow direct synthesis of metal complexes from bare metal electrodes. Systematic studies have been reported and periodically reviewed.22-24 The sacrificial electrode may either be a cathode (Pb, Sn, Hg), or an anode (metals) which is the most usual configuration. The experiments are generally carried out under galvanostatic conditions (10-30 mA cm-2) and so a reference electrode and a potentiostat are not required. Different types of products have been obtained from the simplest complexes to clusters. 

The synthesis of cyclic carbonates in RTILs, via cycloaddition of cathodically activated carbon dioxide to epoxide, has been reported by Deng et al. [139]. Ionic liquids, saturated with CO by bubbling at normal pressure and containing the epoxidic substrate, were electrolyzed in an undivided cell (Cu as cathode. Mg or Al as sacrificial anode). The electrolyses were carried out under potentiostatic conditions at a potential negative enough to the selective reduction of CO to CO (E=-2.4 V vs. 

Potentiostatic coulomctry also offers possibilities for the electrolytic determination (and synthesis) of organic compounds. For example, Meites and Meites demonstrated that trichloroacetic acid and picric acid are quantitatively reduced at a mercury cathode whose potential is suitably controlled -... 

In the E/C synthesis, the first step in which metal nanocrystals are deposited on the substrate is critical. The semiconductor particles grow from the metal particles on a particle-by-particle basis (i.e. each metal particle is chemically transformed to the corresponding semiconductor). The size and size distribution, therefore, in the first step determine the final size of the semiconductor particles. For that reason, it is important to achieve an understanding of the growth mechanism of the metal nanocrystal deposition. Penner and associates studied the electrodeposition of various metal nanoparticles (Ag, Pt, Zn, Cu, Cd) mainly onto basal plane-oriented graphite and also onto Si electrodes [6-11]. The depositions were carried out from dilute aqueous solutions of metal ions using a potentiostatic pulse regime. A short (typically tens of ms) potential pulse was applied followed by open[Pg.174]

Electrochemistry is an excellent method for the selective and controlled production of reduced B12 forms under potentiostatic control. As alkyl halides or alkyl tosylates react quickly and efficiently with Co(I)-corrins [22,91], which are cleanly generated at controlled electrode potentials near that of Co(II)-/Co(I)-couples, electrochemistry provides a suitable method for the synthesis of organometallic B12 derivatives [87]. 

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