(450g) Effects of Mixed Solvents on CO2 Electrocatalytic Reduction

The electrocatalytic conversion of CO₂ (CO2RR) into value-added chemicals and fuels offers a promising, scalable, and sustainable pathway to utilize CO₂. This reaction is typically carried out on metal electrodes in aqueous solutions where the parasitic hydrogen evolution reaction (HER) is prevalent due to water breakdowns. Using aprotic co-solvents is thought to be beneficial for CO2RR because they could alleviate water contents and increase the solubility of CO₂. In addition, mixtures of water with polar aprotic co-solvents such as γ-valerolactone (GVL) have been shown to greatly modulate the catalytic reactivity in the liquid phase.^1,2

Herein, we present our theoretical investigations on the effects of aprotic solvents relevant to CO2RR on gold electrodes. The complex electrochemical metal/solution interfaces are described by a suite of potential-dependent ab initio molecular dynamics (AIMD) and density functional theory (DFT) in the presence of explicit solvent molecules. We first study and elucidate the interfacial structures of GVL/H₂O mixtures under cathodic conditions. Our results indicate that different interactions between co-solvents with water lead to distinct microenvironments at the metal interface. Based on the structural insights, we further examine the reactivity of HER and CO2RR as a function of applied potentials and delineate the effects of different co-solvents on the selectivity of CO2RR in polar aprotic media. Our findings promote the understanding of controlling microenvironments for the electrochemical transformation of CO₂.

References

(1) Mellmer, M. A.; Sanpitakseree, C.; Demir, B.; Bai, P.; Ma, K.; Neurock, M.; Dumesic, J. A. Nat Catal 2018, 1 (3), 199–207.

(2) Mellmer, M. A.; Sanpitakseree, C.; Demir, B.; Ma, K.; Elliott, W. A.; Bai, P.; Johnson, R. L.; Walker, T. W.; Shanks, B. H.; Rioux, R. M.; Neurock, M.; Dumesic, J. A. Nat Commun 2019, 10 (1), 1132.