Pre-Protonation Reaction Pathway for CO₂ Electrolysis to n-Propanol

The electroreduction of CO₂ into high-energy-density n-propanol represent a promising approach for storing intermittent renewable electricity. However, the electrosynthesis of n-propanol encounters substantial challenges owing to the high energy barrier C-C coupling steps and the competition from C₂ products, resulting in exceedingly low selectivity. Herein, we introduce a novel preprotonation reaction pathway in a mixed-coordination copper catalyst to overcome these limitations. Specifically, high-coordination copper sites (HCN-Cu) predominantly generate CO, creating a CO-rich environment for low-coordination copper sites (LCN-Cu) via a spillover effect. The LCN-Cu sites, characterized by their reduced *CO adsorption energy and enhanced water dissociation capability, facilitate the preprotonation of C₁ and C₂ intermediates. Consequently, protonation of *CO to form *COH occurs prior to its dimerization with another *CO molecule, thereby circumventing the traditionally high-energy barrier *CO-*CO coupling process. Density Functional Theory calculations further confirm that the rate-determining step in this pathway shifts from traditional C-C coupling to *COH formation, reducing the reaction energy barrier from 1.63 to 0.98 eV. The lower C-C coupling energy barrier will generate more *C₂ intermediates and continuously couple into C₃, further mitigating competition with C₂ products. Following this preprotonation pathway, the mixed-coordination copper achieves record-high n-propanol Faradaic selectivity of 17.6%.