Electrochemical Reduction of Carbamates and Carbamic Acids: Implications for Combined Carbon Capture and Electrochemical CO2 Recycling

Electrocatalytic reduction of CO2 to CO could represent the first step in solar-driven recycling of CO2 to fuels. While many reports focus on catalyst design or modification of additives such as Lewis or Bronsted acids, there is little focus on modification of the substrate, CO2 itself. Current carbon capture technology employs amines to capture CO2 as carbamates, suggesting that they may serve as a CO2 surrogate, streamlining carbon capture and recycling. Towards this, herein we explore the cyclic voltammetry of seven amines in the presence/absence of CO2. We show that on a glassy carbon electrode in acetonitrile (MeCN) up to -2.7 V vs Fc/Fc(+) in tetrabutylammonium hexafluorophosphate (TBAPF(6)) electrolyte, the amines can only be reduced in the presence of CO2. The potential of the reduction is dependent on the amine identity as well as the protonation state of the resulting species, carbamate versus carbamic acid. Bulk electrolysis experiments indicate little or no reduction to CO and low Faradaic efficiency for formate. This suggests that these amines may be of use in subsequent studies with molecular electrocatalysts that take CO2 to CO and not formate. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.