Pre-Protonation Reaction Pathway for CO 2 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%.