Decoding Electric Double Layer Effects on CO ₂ Electroreduction on Ni–N–C via Multiscale Modeling

High Resolution Image Download MS PowerPoint Slide Understanding the electrocatalyst–electrolyte interface, including electric double layer (EDL) effects, is critical for CO 2 electroreduction (CO 2 RR). However, modeling the EDL’s full complexity, spanning large spatiotemporal scales (∼10 nm, >100 ps) remains a challenge for conventional simulations. Here, we integrate the grand canonical density functional theory (GC-DFT) with large-scale classical molecular dynamics and free energy perturbation (FEP) methods (30,000+ atoms, ns time scale) to model CO 2 reduction to CO on a Ni–N–C/G catalyst under an applied potential of −0.60 V RHE in a 0.5 M KHCO 3 electrolyte. The simulations indicate that under these specific conditions, the EDL substantially promotes CO 2 adsorption (−0.64 eV) and facilitates the two proton-transfer steps while slightly inhibiting CO desorption. Moreover, the FEP simulation results reveal that the interfacial electric field (EF), rather than cation coordination, is primarily responsible for modulating these reaction energetics. Furthermore, a linear correlation is found between the perpendicular dipole moment change (Δμ z ) of adsorbed intermediates and the EF-induced free energy shift (Δ G FEP ), suggesting a useful descriptor for assessing EDL influences. This work demonstrates the value of a multiscale framework for probing interfacial electrochemical phenomena.