Zhen Liu^a, Jiamei Li^a, Wen Jin^a, Tingting Gong^a, Chuanyong Zhu^b,*, Haoqi Xu^a, Chaofan Zeng^a, Min Wang^a,*, Luhua Jiang^a,*

^a College of Materials Science & Engineering, Qingdao University of Science & Technology, Qingdao 266042, PR China

^b College of New Energy, China University of Petroleum (East China) Qingdao, Shandong 266580, PR China

ABSTRACT

Interfacial water plays a significant role in electrochemical reactions involving proton-coupled electron transfer processes, such as CO₂ electrochemical reduction reaction (CO2RR). However, the exact relationship between interfacial hydrogen-bond network and CO2RR performance of in-situ evolved Cu-based catalysts remains poorly understood at a molecular level, posing significant challenges to rational design of catalysts with enhanced selectivity to C₂₊ products. Herein, a series of cationic surfactant-modified Cu₂O/Cu catalysts were constructed, where Cu₂O/Cu was evolved from CuO and identified combining with in-situ and ex-situ studies. Leveraging a combination of in-situ vibrational spectroscopy, electrochemical impedance spectroscopy and molecular dynamics simulation, it is revealed that the surfactants with longer alkyl chains are more conducive to provide a strong hydrogen-bond network, thereby facilitating proton transfer and enhance *H coverage. Moreover, a volcano-type relationship is established between the strong hydrogen-bonded water and C₂₊ selectivity, as excessively fast proton transfer would instead promote the competing hydrogen evolution reaction. This work provides a facile strategy to regulate the interfacial H-bond network by cationic surfactants and elucidates semi-quantitatively the role of interfacial H-bonding network on the CO2RR selectivity.