In electrochem. processes, an oxidn. half-reaction is always paired with a redn. half-reaction. Although systems for reactions such as the redn. of CO2 can be coupled to H2O oxidn. to produce O2 at the anode, large-scale O2 prodn. is of limited value. One may replace a low-value half-reaction with a compatible half-reaction that can produce a valuable chem. compd. and operate at a lower potential. In doing so, both the anodic and cathodic half-reactions yield desirable products with a decreased energy demand. Here the authors demonstrate a paired electrolysis in the case of the oxidative condensation of syringaldehyde and o-phenylenediamine to give 2-(3,5-dimethoxy-4-hydroxyphenyl)benzimidazole coupled with the redn. of CO2 to CO mediated by mol. electrocatalysts. The authors also present general principles for evaluating current-voltage characteristics and power demands in paired electrolyzers.
By: Llorente, Mark J.; Nguyen, Bichlien H.; Kubiak, Clifford P.; Moeller, Kevin D.