Unveiling the Solvation Chemistry and Surface Effects on CO<sub>2</sub> Reduction Reaction Pathways in Nonaqueous Li–CO<sub>2</sub> Batteries
Fan Gao, Mufei Yue, Daniel Wun Fung Cheung, Weimin Yang, Zhonghui He, Yu Gu, Shisheng Zheng, Xiaobin Zhong, Siyuan Ma, Weiping Chen, Jing‐Hua Tian, Jin‐Chao Dong, Jian‐Feng Li
Abstract
Achieving highly reversible Li–CO 2 batteries requires efficient and reversible CO 2 redox reactions. However, the CO 2 reduction reaction (CO 2 RR) mechanism during discharge in nonaqueous electrolytes, strongly influenced by the solvent environment and surface structure, remains unclear. Here, we systematically investigate the CO 2 RR 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 *CO 2 – to produce CO and Li 2 CO 3 . Conversely, low-DN electrolytes promote a surface-mediated pathway due to limited solvation, enhancing direct Li + –*CO 2 – interactions on the electrode surface. Among the various Au( hkl ) surfaces, Au(110) shows superior catalytic activity, greatly enhancing *CO 2 – activation. This research offers crucial insights into the interplay between solvent chemistry and surface structure in the CO 2 RR, guiding future Li–CO 2 batteries optimization.