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要旨

Despite significant theoretical efforts, the identification of the active sites for the electrochemical reduction of CO₂ (CO₂RR) to specific chemical products has remained elusive. This is partially due to insufficient experimental data gathered on clean and atomically well-ordered electrode surfaces. Here, ultrahigh vacuum based preparation methods and surface science characterization techniques are used together with gas chromatography to demonstrate that subtle changes in the preparation of well-oriented Cu(100) and Cu(111) single crystal surfaces drastically affect their CO₂RR selectivity. Copper single crystals with clean, flat, and atomically ordered surfaces are theoretically predicted to yield hydrocarbons. However, these were found experimentally to favour the production of H₂. Only when roughness and defects are introduced, for example through an electrochemical etchingor a plasmatreatment, significant amounts of hydrocarbons are generated. These results clearly indicate that structural and morphological effects are the key factors determining the catalytic selectivity of CO₂RR.