Carbon dioxide reduction by heterogeneous and homogeneous electrocatalysts

Direct reduction of CO2, which is a thermodynamically stable and kinetically rather inert molecule, at metallic electrodes requires highly negative overpotentials and results in a variety of products, whose distribution depends on the nature of the electrode material, solvent and background electrolyte as well as on experimental parameters such as CO2 concentration, temeprature and current density. Homogeneous catalysis both by electrogenerated aromatic radical anions and transition metal complexes drastically affects product selectivity. This communication presents examples of CO2 activation both by direct electrode reduction and by homogeneous electrocatlysis, with particular emphasis on the reduction mechanisms.