Electrolyte-Guided Design of Electroreductive CO Coupling on Copper Surfaces

Abstract

Engineering the interfacial distribution of electrolytic ions can aid in modulating the electrocatalyst performance and efficiency. Using a hybrid quantum-classical modeling approach, we describe how predictive tuning of the solution microenvironment on copper can enhance the efficiency of CO2 reduction (CO2R) to C2 products. We elucidate how competing electrolyte constituents in mixed electrolyte solutions stimulate restructuring of the electrochemical double layer (EDL) and stabilize the OCCO* dimer (* denotes surface adsorbed), with predictions validated in flow reactors using copper gas diffusion electrodes (Cu-GDEs). Our findings highlight how molecular-scale electrolyte engineering with informed models of the EDL can be leveraged to tailor CO2R activity and selectivity toward C2 products.

Surface Engineering of Copper Catalyst through CO* Adsorbate

“…As shown in Figure c, the depletion of electronic charge δρ e is concentrated within a few angstroms from the surface, a behavior typical of charged metals that was also shown in previous DFT calculations . The countering excess solvent charge δρ sol shows a complex oscillating profile of alternating signs; this results from the calculated ionic distributions and their associated solvation shells captured in the ESM-RISM method, as shown in Figure S1.2 of the Supporting Information and our previous work . Interestingly, at the atomic scale, the electric “double layer” actually consists of many layers.…”

Pulse Symmetry Impacts the C2 Product Selectivity in Pulsed Electrochemical CO2 Reduction

“…31,32 DFT simulations have demonstrated the effects of cations on eCO 2 R, showing that cations can change the free energy landscape and stabilize species containing C−C bonds and that coadsorbed K* strengthens CO 2 R intermediates' binding, 33−35 which can enhance the efficiency of C 2 product formation. 36 Computational data also shows that K + adsorption only becomes favorable at potentials more negative of −1.5 V vs RHE on Cu(100). 34 The observation that the largest negative interfacial charge coincides with the highest C 2 selectivity leads us to propose that the symmetric pulse optimizes the double layer reaction environment for important C 2 intermediates by taking advantage of the cation catalytic promoter effect to accelerate dimerization in addition to increasing the CO interaction strength with the electric field, which was suggested in recent work by Liu et al to enhance C 2 selectivity.…”

“…A large surface charge density leads to a strong interfacial electric field, which has been proposed to drive CO 2 adsorption and stabilize critical dipolar and polarizable eCO 2 R intermediates . These adsorbed intermediates have been shown to have a strong double layer electric field dependence, and when there is a large negative electric field, species with a positive dipole moment (*CO 2 , *CO, *OCCO, and *OCCHO) are stabilized. , DFT simulations have demonstrated the effects of cations on eCO 2 R, showing that cations can change the free energy landscape and stabilize species containing C–C bonds and that coadsorbed K* strengthens CO 2 R intermediates’ binding, − which can enhance the efficiency of C 2 product formation . Computational data also shows that K + adsorption only becomes favorable at potentials more negative of −1.5 V vs RHE on Cu(100) …”

A Hybrid Quantum–Classical Study of Ion Adsorption at the Copper Electrode

“…Using this computational framework, we present a series of calculations that capture thermodynamic and electrochemical descriptions of aqueous K + , Cs + , Cl – , Br – , and I – ions at the Cu(100) and Cu(111) interfaces. These atoms are chosen because specific alkali and halide ions in the electrolyte have been observed to have a pronounced effect on possible reaction energetics and product selectivities for CO 2 RR on Cu. ,,,− Our survey includes calculations at a selection of electrochemically relevant potentials and a range of ion–electrode distances. The DFT/ESM-RISM approach makes a survey at this level of detail possible within modern computational resources and enables us to construct potential of mean force (PMF) curves as a function the ion’s identity, copper electrode facet, ion position, and system potential.…”