• Energy Research

CO2 capture technologies based on chemisorption present the potential to lower net emissions of CO2 into the atmosphere. The electrochemical upgrade of captured CO2 to value-added products would be particularly convenient. Here we find that this goal is curtailed when the adduct of the capture molecule with CO2 fails to place the CO2 sufficiently close to the site of the heterogeneous reaction. We investigate tailoring the electrochemical double layer to achieve the valorization of chemisorbed CO2 in an aqueous monoethanolamine electrolyte. We reveal, using electrochemical studies and in situ surface-enhanced Raman spectroscopy, that a smaller double layer distance correlates with improved activity for CO2 to CO from amine solutions. With the aid of an alkali cation and accelerated mass transport by system design—temperature and concentration—we demonstrate amine–CO2 conversion to CO with 72% Faradaic efficiency at 50 mA cm–2. Electrochemical conversion of CO2 into high-value products is attractive for lowering net carbon emissions. Lee et al. present the valorization of chemisorbed CO2 to CO in an aqueous monoethanolamine electrolyte via tailoring of the electrochemical double layer, with 72% Faradaic efficiency at 50 mA cm–2.

CO2 capture technologies based on chemisorption present the potential to lower net emissions of CO2 into the atmosphere. The electrochemical upgrade of captured CO2 to value-added products would be particularly convenient. Here we find that this goal is curtailed when the adduct of the capture molecule with CO2 fails to place the CO2 sufficiently close to the site of the heterogeneous reaction. We investigate tailoring the electrochemical double layer to achieve the valorization of chemisorbed CO2 in an aqueous monoethanolamine electrolyte. We reveal, using electrochemical studies and in situ surface-enhanced Raman spectroscopy, that a smaller double layer distance correlates with improved activity for CO2 to CO from amine solutions. With the aid of an alkali cation and accelerated mass transport by system design—temperature and concentration—we demonstrate amine–CO2 conversion to CO with 72% Faradaic efficiency at 50 mA cm–2. Electrochemical conversion of CO2 into high-value products is attractive for lowering net carbon emissions. Lee et al. present the valorization of chemisorbed CO2 to CO in an aqueous monoethanolamine electrolyte via tailoring of the electrochemical double layer, with 72% Faradaic efficiency at 50 mA cm–2.

The carbon dioxide electroreduction reaction (CO2RR) provides ways to produce ethanol but its Faradaic efficiency could be further improved, especially in CO2RR studies reported at a total current density exceeding 10 mA cm−2. Here we report a class of catalysts that achieve an ethanol Faradaic efficiency of (52 ± 1)% and an ethanol cathodic energy efficiency of 31%. We exploit the fact that suppression of the deoxygenation of the intermediate HOCCH* to ethylene promotes ethanol production, and hence that confinement using capping layers having strong electron-donating ability on active catalysts promotes C–C coupling and increases the reaction energy of HOCCH* deoxygenation. Thus, we have developed an electrocatalyst with confined reaction volume by coating Cu catalysts with nitrogen-doped carbon. Spectroscopy suggests that the strong electron-donating ability and confinement of the nitrogen-doped carbon layers leads to the observed pronounced selectivity towards ethanol. The electroreduction of CO2 to ethanol could enable the clean production of fuels using renewable power. This study shows how confinement effects from nitrogen-doped carbon layers on copper catalysts enable selective ethanol production from CO2 with a Faradaic efficiency of up to 52%.

The carbon dioxide electroreduction reaction (CO2RR) provides ways to produce ethanol but its Faradaic efficiency could be further improved, especially in CO2RR studies reported at a total current density exceeding 10 mA cm−2. Here we report a class of catalysts that achieve an ethanol Faradaic efficiency of (52 ± 1)% and an ethanol cathodic energy efficiency of 31%. We exploit the fact that suppression of the deoxygenation of the intermediate HOCCH* to ethylene promotes ethanol production, and hence that confinement using capping layers having strong electron-donating ability on active catalysts promotes C–C coupling and increases the reaction energy of HOCCH* deoxygenation. Thus, we have developed an electrocatalyst with confined reaction volume by coating Cu catalysts with nitrogen-doped carbon. Spectroscopy suggests that the strong electron-donating ability and confinement of the nitrogen-doped carbon layers leads to the observed pronounced selectivity towards ethanol. The electroreduction of CO2 to ethanol could enable the clean production of fuels using renewable power. This study shows how confinement effects from nitrogen-doped carbon layers on copper catalysts enable selective ethanol production from CO2 with a Faradaic efficiency of up to 52%.

Bipolar membranes maintain a steady pH in electrolytic cells through water autodissociation at the interface between their cation- and anion-exchange layers. We analyze the balance of electric field and catalysis in accelerating this reaction.

Bipolar membranes maintain a steady pH in electrolytic cells through water autodissociation at the interface between their cation- and anion-exchange layers. We analyze the balance of electric field and catalysis in accelerating this reaction.