Unveiling the Solvation Chemistry and Surface Effects on CO₂ Reduction Reaction Pathways in Nonaqueous Li-CO₂...

Achieving highly reversible Li-CO₂ batteries requires efficient and reversible CO₂ redox reactions. However, the CO₂ reduction reaction (CO₂RR) mechanism during discharge in nonaqueous electrolytes, strongly influenced by the solvent environment and surface structure, remains unclear. Here, we systematically investigate the CO₂RR on atomically flat Au(hkl) single crystal surfaces, providing direct spectral evidence of vital surface/intermediate species using in situ Raman spectroscopy. Our findings, combined with theoretical calculations, reveal that high-donor-number (DN) electrolytes facilitate a solution-mediated pathway, where Li⁺ forms stable solvation structures with solvent molecules that react with *CO₂^- to produce CO and Li₂CO₃. Conversely, low-DN electrolytes promote a surface-mediated pathway due to limited solvation, enhancing direct Li⁺-*CO₂^- interactions on the electrode surface. Among the various Au(hkl) surfaces, Au(110) shows superior catalytic activity, greatly enhancing *CO₂^- activation. This research offers crucial insights into the interplay between solvent chemistry and surface structure in the CO₂RR, guiding future Li-CO₂ batteries optimization.