Oxy-reductive C-N bond formation via pulsed electrolysis.

Abstract

Co-electrolysis of CO₂ with simple N-species is an appealing route to sustainable fabrication of C-N bond containing products. A prominent challenge in this direction is to promote the C-N coupling step in place of the established CO₂ reduction pathways. This can be particularly difficult when relying on solution-based species (e.g., NH₃) to intercept intermediates that are continually being reduced on heterogeneous catalyst surfaces. In light of this, we introduce oxy-reductive pulsed electrocatalysis as a tool for C-N bond formation. The reaction routes opened through this method involve both partial reduction and partial oxidation of separate reactants on the same catalyst surface in parallel to co-adsorb their activated intermediates proximal to one another. Using CO₂ and NH₃ as model reactants, the end result is an enhancement of selectivity and formation rates for C-N bond containing products (urea, formamide, acetamide, methylamine) by factors of 3-20 as compared to static electrolysis in otherwise identical conditions. An array of operando measurements is carried out to pinpoint the key factors behind this performance enhancement. Finally, the oxy-reductive coupling strategy is extended to additional carbon and nitrogen reactants and is further applied to C-S coupling.