Theoretical Investigation of the Adsorbate and Potential‐Induced Stability of Cu Facets During Electrochemical CO2 and CO Reduction

Using grand canonical density functional theory calculations and microkinetic modelling, we describe an approach for calculating potential and adsorbate-dependent contributions to surface energies under reaction conditions. We identify that CO*, a key reaction intermediate for carbon dioxide reduction (CO2RR), exhibits higher kinetically and thermodynamically accessible coverages on (100) relative to (111) facets on Cu, which can translate into an increased relative stabilization of the (100) facet during CO2RR.

Abstract

The activity and product selectivity of electrocatalysts for reactions like the carbon dioxide reduction reaction (CO₂RR) are intimately dependent on the catalyst's structure and composition. While engineering catalytic surfaces can improve performance, discovering the key sets of rational design principles remains challenging due to limitations in modeling catalyst stability under operating conditions. Herein, we perform first-principles density functional calculations adopting implicit solvation methods with potential control to study the influence of adsorbates and applied potential on the stability of different facets of model Cu electrocatalysts. Using coverage dependencies extracted from microkinetic models, we describe an approach for calculating potential and adsorbate-dependent contributions to surface energies under reaction conditions, where Wulff constructions are used to understand the morphological evolution of Cu electrocatalysts under CO₂RR conditions. We identify that CO*, a key reaction intermediate, exhibits higher kinetically and thermodynamically accessible coverages on (100) relative to (111) facets, which can translate into an increased relative stabilization of the (100) facet during CO₂RR. Our results support the known tendency for increased (111) faceting of Cu nanoparticles under more reducing conditions and that the relative increase in (100) faceting observed under CO₂RR conditions is likely attributed to differences in CO* coverage between these facets.

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