Potential-Dependent Competitive Electroreduction of CO₂ into CO and Formate on Cu(111) from an Improved H Coverage-Dependent Electrochemical Model with Explicit Solvent Effect

Abstract

An improved density functional theory-based H coverage-dependent electrochemical model with explicit solvent effect is proposed for Cu (111), which is used to identify potential-dependent initial competitive CO 2 electroreduction pathways considering HER. We find that a chemisorbed CO 2 molecule at the present electrode/aqueous interface can be spontaneously formed and the overpotentials can affect its coordination pattern. The Eley−Rideal mechanism may be more favorable during the initial CO 2 electroreduction into CO, whereas chemisorbed CO 2 reacting with adsorbed H into HCOO − via the Langmuir− Hinshelwood mechanism is more facile to occur. The analyses of energetics suggest that the low overpotentials have a negligible influence on CO and HCOO − formation, and HCOO − species with monodentate and bidentate configurations may also parallelly form with the surmountable barriers at room temperature. However, the high potentials have an interruptive effect on initial CO 2 electroreduction because of the significantly increased barriers, indicating that the chemisorbed CO 2 can be stabilized by imposing more negative potentials and thus going against initial CO 2 electroreduction. By analyzing the competing HER with initial CO 2 electroreduction into CO, we find that HER is competitive with initial CO formation because of the required lower overpotentials. Simultaneously, the present study shows that the blocked Cu surface by adsorbed H and CO can explain why the initial CO formation pathway is unfavorable at the high overpotentials. Our present conclusions can also confirm the previous experimental report on initial formation of CO and HCOO − .

Designing Copper‐Based Catalysts for Efficient Carbon Dioxide Electroreduction

“…The CO 2 electroreduction has two two‐electron‐transfer products, that is, CO and formate (HCOO − ). [ 59,60 ] After the initial CO 2 activation and CO 2 •− radical formation, [ 61 ] the configuration of CO 2 •− on the catalyst surface determines the reaction pathway. The adsorption through strong metalcarbon bonds or metal–carbon/metal–oxygen bonds can generate carboxyl (*COOH) intermediate, the precursor of CO, after electron and proton transfer.…”

Mechanistic insights into the effect of halide anions on electroreduction pathways of CO2 to C1 product at Cu/H2O electrochemical interfaces

“…−1.35 and −0.90 eV for CO 2 electroreduction into CH 4 and CH 3 OH product at clean Cu(111)/H 2 O interface, which both are notably less negative than those of Br − modified Cu(111)/H 2 O interface. 36,45 Additionally, the reaction free energy for CO 2 electroreduction into CH 4 and CH 3 OH product at I − modified Cu(111)/H 2 O interface is also significantly more negative than that of clean Cu(111)/H 2 O interface (ca. −2.60 and −1.40 eV vs. −0.90 eV).…”

Grazing incidence X-Ray diffraction: identifying the dominant facet in copper foams that electrocatalyze the reduction of carbon dioxide to formate

“…13 Further supporting these conclusions is the more recent study in which the authors concluded that on Cu(111) “the Eley–Rideal reaction via proton-electron transfer may be more favorable during initial CO 2 electroreduction into CO through intermediate COOH, whereas chemisorbed CO 2 reacting with a surface-adsorbed H into HCOO − via Langmuir–Hinshelwood mechanical is more facile to occur ”. 14 Importantly, HCOO − is kinetically favored (lower transition state energies) over CO formation.…”