Direct Electrosynthesis of Alkylamines from Carbon Dioxide and Nitrate

Abstract

Electrolysis of abundant inorganic wastes driven by renewable energy sources is a sustainable way to produce valuable organic compounds. Production of alkanes, alkenes, and alcohols from carbon dioxide electroreduction has been demonstrated, but synthesizing organonitrogen molecules such as alkylamines is largely beyond the reach of currently known electrocatalysis. This talk presents the first electrochemical reaction that converts carbon dioxide and nitrate to organonitrogen compounds, principally methylamine, in aqueous media under ambient conditions catalyzed by a cobalt β-tetraaminophthalocyanine molecular catalyst supported on carbon nanotubes. The overall reaction, which involves the transfer of 14 electrons and 15 protons to form 1 methylamine molecule, is an unprecedented eight-step catalytic cascade enabled by the coupling of two reactive intermediates near the catalyst surface. The key C-N bond-forming step is found to be the spillover of hydroxylamine from nitrate reduction and its subsequent spontaneous condensation with formaldehyde from carbon dioxide reduction. This study provides a successful example of sustainable alkylamine synthesis from inorganic carbon and nitrogen wastes, which is extendable to other valuable organonitrogen compounds.