Electroactive species in reactive CO2 capture

Electrochemical reactive carbon dioxide capture (eRCC) couples CO 2 absorption and conversion, yet the identity of the true electroactive carbon species remains contested. Across carbonate- and amine-based systems, accumulating evidence demonstrates that dissolved CO 2 , regenerated from capture equilibria, dominates CO formation under practical operating conditions. Transport-controlled measurements reveal that CO generation rate scales with dissolved CO 2 activity and is bounded by its mass-transfer limit. Direct carbamate reduction emerges only within a narrow, deeply reducing regime and does not generally replace molecular CO 2 as the operative substrate. In contrast, specific diamine-derived zwitterionic carbamates can attain kinetic relevance when structural and interfacial factors align. Clarifying this potential-dependent crossover resolves longstanding ambiguity and establishes interfacial CO 2 availability, rather than bulk speciation alone, as the decisive parameter for rational eRCC design. • The electroactive carbon species in eRCC is critically reassessed. • A mechanistic framework connecting CO 2 capture equilibria and electroreduction is developed. • Evidence for dissolved CO 2 and carbamate pathways is systematically compared.