Dynamic Reoxidation/Reduction-Driven Atomic Interdiffusion for Highly Selective CO₂ Reduction toward Methane

Abstract

Understanding the dynamic structural reconstruction/transformation of catalysts during electrochemical CO₂ reduction reaction (CO₂RR) is highly desired for developing more efficient and selective catalysts, yet still lacks in-depth realization. Herein, we study a model system of copper nanowires with various degrees of silver modifications as electrocatalysts for CO₂RR. Among them, the Cu₆₈Ag₃₂ nanowire catalyst achieves the highest activity and selectivity toward methane with an extremely high faradaic efficiency of ∼60%, about 3 times higher than that of primitive Cu nanowires, and even surpasses the most efficient catalysts for producing methane. By using <i>in situ</i> grazing-angle X-ray scattering/diffraction, X-ray absorption spectroscopy, and Raman techniques, we found that the Cu₆₈Ag₃₂ nanowires underwent an irreversible structural reconstruction and well-stabilized chemical state of Cu on the catalyst surface under the working CO₂RR conditions, which greatly facilitates the CO₂ to methane conversion. Further analysis reveals that the restructuring phenomenon can be ascribed to a reoxidation/reduction-driven atomic interdiffusion between Cu and Ag. This work reveals the first empirical demonstration by deploying comprehensive <i>in situ</i> techniques to track the dynamic structural reconstruction/transformation in a model bimetallic system, which not only establishes a good understanding of the correlation between catalyst surface structure and catalytic selectivity but also provides deep insights into designing more developed electrocatalysts for CO₂RR and beyond.