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Cetyltrimethylammonium bromide (CTAB) has been used to enhance the selectivity of CO2 electrochemical reduction. Traditionally, this selectivity was attributed to repulsion of water molecules due to a CTAB self-assembled monolayer, which forms under negative potential and disassembles at positive voltage due to electrostatic repulsions. In this report, using in operando interface sensitivity sum frequency generation spectroscopy, we investigated the self-assembly behavior of CTAB across a broad electrochemical potential range. We observed that CTAB molecules form a stable monolayer at the Stern layer over the entire potential scan, even when the electrodes are positively charged. Rather than disassembling, the CTAB molecules reorient themselves to balance the electrostatic interactions and the non-covalent hydrophobic effects, the latter being the primary driving force maintaining the monolayer at a positive potential. This finding contrasts the traditional view that CTAB monolayers are absent when the electrodes are positively charged, indicating a stable and ordered monolayer with respect to the electrostatic repulsions at liquid/electrode interfaces. The balance between non-covalent and electrostatic interactions offers a facile and reversible electrochemical method to control the local environment and dominating interactions at the Stern layer of the electrode surface, thus providing a means for engineering a micro-electrochemical environment. 

Abstract Hybrid electrodes with improved O₂tolerance and capability of CO₂conversion into liquid products in the presence of O₂are presented. Aniline molecules are introduced into the pore structure of a polymer of intrinsic microporosity to expand its gas separation functionality beyond pure physical sieving. The chemical interaction between the acidic CO₂molecule and the basic amino group of aniline renders enhanced CO₂separation from O₂. Loaded with a cobalt phthalocyanine‐based cathode catalyst, the hybrid electrode achieves a CO Faradaic efficiency of 71 % with 10 % O₂in the CO₂feed gas. The electrode can still produce CO at an O₂/CO₂ratio as high as 9:1. Switching to a Sn‐based catalyst, for the first time O₂‐tolerant CO₂electroreduction to liquid products is realized, generating formate with nearly 100 % selectivity and a current density of 56.7 mA cm⁻²in the presence of 5 % O₂.