@

초록

Tuning the coordination environment of atomically dispersed Cu sites is crucial for steering CO2 reduction reaction (CO2RR) selectivity toward multi-carbon products. Herein, we report mixed-coordination Cu single-atom catalysts (Cu–SACs–N–CDs) derived from a Cu–dopamine complex and tannic acid, enabling modulation of Cu–Nx and Cu–Nx/O motifs via Cu loading. Structural analyses reveal a loading-dependent evolution from uniform Cu–Nx to heterogeneous Cu–Nx+Cu–Nx/O sites with mixed-valence Cu species. Flow-cell CO2RR measurements exhibit a volcano-type selectivity trend. The Cu(0.8 wt%)–SACs–N–CDs catalyst favors CO formation, whereas Cu(3.3 wt%)–SACs–N–CDs achieves 44.1% ethanol Faradaic efficiency at 100 mA·cm−2 with 50 h stability, accounting for over 65% of C2 products. In situ Raman and ATR-FTIR spectroscopy reveal enhanced *CO coupling toward *OCCO and OCCHO intermediates on mixed Cu sites, while DFT calculations confirm that the reduced OCCO formation barrier facilitates the ethanol pathway and promotes C1-to-C2 selectivity.

키워드