(187e) Unraveling Selectivity Toward Multi-Carbon Products for Electrochemical CO(2) Reduction

The ability to selectively synthesize multi-carbon (C₂₊) products through electrochemical reduction of CO₍₂₎ (CO₍₂₎R) is one of the grand challenges in the field. The poor selectivity stems from the complexity of the CO₍₂₎R reaction network that involves numerous branching pathways leading to various products. Current understanding supports CO dimerization as the sole pathway toward C₂₍₊₎ products, which offers limited explanation to facet dependency and significantly constrains the discovery of new catalytic materials beyond copper (Cu), the only materials so far able to catalyze C₂₊ formation from CO₍₂₎. This challenge has driven us to explore new avenues for C₂₊ formation from CO₍₂₎ and extract simple descriptors from the mechanistic insights to better describe CO₍₂₎R. In this presentation, we identify the critical steps toward C₂ products on Cu through a combination of density functional theory and micro-kinetic modeling. We elucidate the unambiguous formation of atomic carbon under usual CO₍₂₎R conditions and its importance in directing C₂₊ selectivity. We present an ab initio microkinetic model that accurately reproduces the experimental trends of CO₍₂₎R at varying potential and pH, which provides the first theoretical explanation to facet-dependent CO₍₂₎R selectivity on Cu and elucidates key elements defining the relative C₂₍₊₎/methane (C₁) production rates. We further introduce two simple energy descriptors, CO and C binding strength, that define the C₁ and C₂ selectivity for a broad range of metal and metal alloy catalysts.