Highly active and selective dual-atom modified MXene catalysts for carbon dioxide reduction to ethanol

Abstract

Developing electrocatalysts for converting CO₂ into value-added multicarbon products is a fascinating energy strategy, but it still suffers from a high energy barrier, low selectivity and limited mechanism understanding. Herein, an efficient solution by constructing MXene-based non-noble metal dual-atom catalysts (DACs) is proposed. Experimental results indicate that the homonuclear Co–Co DAC with an asymmetric C–C coupling pathway of *CH₃–CO can reduce CO₂ to ethanol at an ultralow limiting potential (U_L) of 0.22 V, much lower than that of the well-known Cu (111) surface (0.94 V). Such high activity is attributed to its relatively moderate d-band center, which enables d-electrons to appropriately fill the antibonding orbitals to properly adsorb the reaction intermediates. Upon introducing Fe atoms, the Co–Fe heteronuclear DAC exhibits better ethanol selectivity due to the synergistic interaction between dual-atoms via the electron delocalization mechanism (EDM), which favors the step of C–C coupling (−0.67 eV) over the competing hydrogenation reaction (−0.14 eV). Moreover, an easily computable descriptor ψ related to dual-atom electronegativity is proposed, which can predict the reaction U_L for quick screening of MXene-based DACs with sufficient precision (R² = 0.93). These findings provide not only novel excellent candidate catalysts for CO₂ reduction with an elucidated reaction mechanism, but also effective guidance for designing high-performance DACs for multicarbon products.