Elucidating the Synergistic Role of K-Co-Cu Ternary Interfaces in Selective CO2 Hydrogenation to Ethylene: A Combined DFT and Microkinetic Modeling Study

Abstract

Direct CO₂ hydrogenation to value-added hydrocarbons provides a pivotal route for carbon resource recycling, yet achieving high selectivity toward specific products remains a significant challenge. In this study, we combined density functional theory calculations with microkinetic modeling (MKM) to systematically investigate the catalytic performance of a series of K₂O-promoted Co₂C surfaces, including K/Co₂C, K/Cu₄-Co₂C, K/Cu-Co₂C(int), and K/Co₂C-Cu(inv) for CO₂ hydrogenation. The computational results reveal that both the Co/Cu atomic ratio and the interfacial structure decisively govern the catalytic performance. In particular, the K/Cu-Co₂C(int) surface, with a Co:Cu atomic ratio of 1:1 and the largest heterogeneous interface, exhibits moderate adsorption strengths for CO₂ and H₂, effectively mitigating the active site poisoning that is prevalent on the pristine K/Co₂C surface. Potential energy surface analyses demonstrate that this tailored interfacial structure significantly reduces the barriers for both the reverse water-gas shift reaction and C–C coupling, while kinetically suppressing the competing CO-insertion and methanation pathways. Furthermore, MKM and degree of rate control analyses confirm that the K/Cu-Co₂C(int) interface model sustains balanced surface species coverage and delivers C₂H₄ turnover frequency several orders of magnitude higher than that of the other catalyst configurations across 500–700 K. This work clarifies the atomic-scale modulation mechanism of K-Co-Cu ternary interfaces and provides guidance for the rational design of catalysts for selective CO₂-to-olefins conversion.