Paired Electrochemical Processes: Overview, Systematization, Selection Criteria, Design Strategies, and Projection

Abstract

In most commercial electrochemical processes, only one of the two sides of the cell produces a desirable reaction, whereas the complementary reaction at the other side simply avoids interference with the target process and/or offers fast kinetics as not to limit it. An overview of several possible paired reaction schemes and their advantages is given, accompanied with specific thermodynamic and kinetic selection criteria, cell and reaction design strategies, and examples from the organic, inorganic, and environmental areas. The unnecessary nomenclature dispersion in this field (e.g., combined, concurrent, conjugate, convergent, coupled, divergent, dual, duet, linear, paired, parallel, simultaneous and synchronous electrochemical processes) is revised and a simple, consistent classification, as well as a homogeneous schematization system, is proposed.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

“…891 The most important process in this category is probably the Chlor-alkali process wherein chlorine and sodium hydroxide are formed at the anode and cathode, respectively. 892 Millions of tons of NaOH and chlorine have been produced in this fashion.…”

“…891 For example, De Vos and co-workers devised a system to simultaneously synthesize diacids and diol derivatives from the electrolysis of dienes in the presence of CO 2 , TFA, and trimethylamine (Figure 50B, top) in an undivided cell. 898 The diene can undergo two consecutive anodic oxidations to yield acyl-protected diols.…”

“…891 The synthesis of D-arabinose from sodium gluconate provides an example—in the catholyte, this oxidative decarboxylation was mediated by iron salts and HO • free radicals while the anodic process is a direct decarboxylation. 901 …”

Paired electrocatalytic hydrogenation and oxidation of 5-(hydroxymethyl)furfural for efficient production of biomass-derived monomers

“…18 Electrochemical half-reactions occur in pairs, yet many commercialized electrochemical processes only utilize one of the two electrodes for generation of desired products. 19 For example, electrochemical reductions are typically paired with water oxidation as a benign counter reaction. However, water oxidation has sluggish kinetics and the oxygen gas produced is not valuable.…”

Evidence of Radical Intermediate Generated in the Electrochemical Oxidation of Iodide

“…Finally, we note the relevance of this report on the possible application of the radical intermediate I • in electrosynthesis, in particular as an electrogenerated reactant or intermediate. [32][33][34] Given the recent renewed interest in electrosynthesis, [33] the application of this reactant could allow new or optimized transformations. For example, ionic halides are common intermediates in electrochemically driven reactions, and there are reports of Cl • , I • , Br + and iodium (I + ) as electrogenerated reactants, as Frontana-Uribe et al point out.…”