Calculations of Product Selectivity in Electrochemical CO₂ Reduction

Abstract

CO2 can be reduced electrochemically to form valuable chemicals such as hydrocarbons and alcohols using copper electrodes, whereas the other metal electrodes tested so far mainly form CO or formate, or only the side product, H2. Accurate modeling of electrochemical reaction rates including the complex environment of an electrical double layer in the presence of an applied electrical potential is challenging. We show here that calculated rates, obtained using a combination of density functional and rate theory, are in close agreement with available experimental data on the formation of the various products on several metal electrodes and over a range in applied potential, thus demonstrating the applicability of the theoretical methodology. The results explain why copper electrodes give a significant yield of hydrocarbons and alcohols, and why methane, ethylene, and ethanol are formed in electroreduction rather than methanol, which is the main product when H2 gas reacts with CO2 on copper catalyst. The insight obtained from the calculations is used to develop criteria for identifying new and improved catalysts for electrochemical CO2 reduction.

Polyoxometalate-based electron transfer modulation for efficient electrocatalytic carbon dioxide reduction

“…[1][2][3][4] However, the uncontrolled multiple coupling processes of electron/protons in CO 2 RR lead to various reaction pathways, which always generate a number of different products, causing low faradaic efficiency (FE) and selectivity. [5][6][7] In addition, from the perspective of reaction thermodynamics, the equilibrium potentials for most CO 2 RR half-reactions (e.g. CO 2 + 2H + + 2e ¼ CO + H 2 O, E ө ¼ À0.11 V vs. RHE, pH ¼ 7) are close to those of the hydrogen evolution reaction (HER) in aqueous electrolyte (E ө ¼ À0.095 V vs. RHE pH ¼ 7), generating an additional competing reaction.…”

Cu2O Nanoparticles with Both {100} and {111} Facets for Enhancing the Selectivity and Activity of CO2 Electroreduction to Ethylene

“…Among the available electrocatalysts, copper is unique because it can produce various hydrocarbons and alcohols and because it can absorb CO intermediates well, facilitating the subsequent C–C coupling for C 2+ production . Ethylene (C 2 H 4 ), an important raw material, is one of the main C2 products over Cu electrodes . However, due to the simultaneous production of H 2 and other C1 species (i.e., CO, CH 4 ), the Faradaic efficiency for the production of C 2 H 4 (FE C2H4 ) on metallic Cu is usually low .…”

“…[16][17][18][19] Ethylene (C 2 H 4 ), an important raw material, is one of the main C2 products over Cu electrodes. [20] However, due to the simultaneous production of H 2 and other C1 species (i.e., CO, CH 4 ), the Faradaic efficiency for the production of C 2 H 4 (FE C 2 H 4 ) on metallic Cu is usually low. [21][22][23][24] Efforts to improve the FE C 2 H 4 of Cu-based catalysts have focused on optimizing the sizes, morphologies, and exposed crystal facets of metallic Cu NPs.…”

Biomimetic Nitrogen Fixation Catalyzed by Transition Metal Sulfide Surfaces in an Electrolytic Cell

“…Explicit inclusion of water and calculations of the proton–electron transfer energy barriers in the simulations would significantly increase the computational effort required and thus, is not included in the present study. However, the presence of water is known to stabilize some species by hydrogen bonding .…”

“…Expliciti nclusion of water and calculations of the proton-electron transfer energy barriers [84,85] in the simulations would significantly increaset he computational effort required and thus, is not included in the present study.H owever,t he presence of water is known to stabilize somes peciesb yh ydrogen bonding. [86] For example, NH 2 is anticipated to be slightly more stable in the vicinity of water but Nw ill not be affected by the water layer.P revious studies have appraisedt he stabilization effects of water to be smaller than 0.1 eV per hydrogen bond.…”