Double layer charging driven carbon dioxide adsorption limits the rate of electrochemical carbon dioxide reduction on Gold

Abstract

Electrochemical CO 2 reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO 2 reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO 2 adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO 2 adsorption at intermediate ones, and CO 2 mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO 2 and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport.

Electrosorption at metal surfaces from first principles

“…• Major differences between CHE and FGC calculations will occur for adsorbates with significant dipole moments, whenever the work function change per adsorbate is large. This is in line with other studies 30,40 and was noted early 7,98 . The improved description at the FGC level comes at a somewhat increased computational cost. This does not so much refer to the actual DFT calculations themselves, thanks to efficient implementations of current implicit solvation models.…”

“…The capabilities of FGC approaches have been highlighted in several publications and include a potential-dependence of chemical reaction steps 8,[29][30][31]39,40 , potential-induced surface reconstructions or shifts of stable adsorption sites 5,11,13,41 . However, there is presently still limited understanding of the methodological differences between the still prevalent zerocharge CHE and the variable-charge FGC approaches.…”

Coupled Copper–Zinc Catalysts for Electrochemical Reduction of Carbon Dioxide

“…A recent study, based on experiments and multiscale modeling, found that even the rate-limiting step is dependent on the applied potentials. [54] Thirdly, the oxidation state of Zn under the CO 2 RR, that is, the nature of the active sites, is not clear. By operando X-ray absorption fine-structure spectroscopy measurements, Jeon et al [43] demonstrated the coexistence of cationic Zn species and metallic Zn during the CO 2 RR.…”

Momentum Relaxed, Plasmon-Resonant Vibrational Sum Frequency Generation of Electrochemical Interfaces: Direct Observation of Carbon Dioxide Electroreduction on Gold

“…This is especially true for CO 2 electroreduction on Au electrodes because weak CO adsorption leads to very low surface coverage during steady state turnover. 24,25 Consequently, this method answers a long-standing challenge in Au electrocatalysis, and promises to inform a variety of processes occurring at active electrochemical interfaces.…”