Electrochemical Reduction of CO<sub>2</sub>: A Common Acetyl Path to Ethylene, Ethanol or Acetate
Monsuru Olatunji Dauda, John Hendershot, Mustapha Bello, Junghyun Park, Alvaro Loaiza Orduz, Nicholas Lombardo, Orhan Kizilkaya, Phillip Sprunger, Anthony Engler, Craig Plaisance, John Flake
Abstract
Ethylene is well known as the primary product of CO 2 reduction at Cu electrocatalysts using zero-gap membrane electrode assembly cells with gas diffusion cathodes. Other types of Cu electrocatalysts including oxide-derived Cu, CuSn and CuSe yield relatively more C 2 oxygenates; however, the mechanisms for C 2 product selectivity are not well established. This work considers selectivity trends of Cu-P 0.065 , Cu-Sn 0.03 , and Cu 2 Se electrocatalysts made using a standard one pot synthesis method. Results show that Cu-P 0.065 electrocatalysts (Cu δ + = 0.13) retain ethylene as a primary product with relatively higher Faradaic efficiencies (FE = 43% at 350 mA cm −2 ) than undoped Cu electrocatalysts (FE = 31% at 350 mA cm −2 ) at the same current density. The primary CO 2 reduction product at Cu-Sn 0.03 (Cu δ + = 0.27) electrocatalysts shifts to ethanol (FE = 48% at 350 mA cm −2 ) while CO 2 reduction at Cu 2 Se (Cu δ + = 0.47) electrocatalysts favor acetate production (FE = 40% at 350 mA cm −2 ). Based on these results, we propose a common acetyl intermediate and a mechanism for selective formation of ethylene, ethanol or acetate based on the degree of partial positive charge ( δ + ) of Cu reaction sites.