Electrosorption and heterogeneous electrocatalysis in electro-organic synthesis reactions

Abstract

Heterogeneous electrocatalysis of organo-electrosynthesis reactions is not very frequently encountered. The selectivity and yield of electro-organic synthesis reactions, consisting of series of charge transfer and chemical steps, are sometimes influenced significantly by heterogeneous electrocatalysis. It modifies mainly the rates of consecutive chemical steps rather than the rate of charge transfer. The underlying electrosorption of reactive organic intermediates (radicals and radical ions) and reactant molecules is generally due to weak adsorption or physisorption, and not due to chemisorption. Therefore most often the catalytic acceleration of one reaction in preference to another competing route is caused by adsorptive enhancement of reactant surface concentration rather than by adsorptive ‘chemical activation’ of the reactants. Thereby the main part of an electrosorbed molecule and intermediate remains chemically unchanged. This is very different from electrocatalysis in the degradative electrochemical conversion of hydrocarbons and oxygen in fuel cells.