Molecularly Engineered Self-Assembled Molecular Layer for pH-Tolerant CO2 Electroreduction With Enhanced Activity and Stability.

The electrochemical CO2 reduction is crucial for achieving carbon neutrality, wherein the catalytic performance is governed not only by the intrinsic catalytic activity but also by the microenvironment of the triple-phase interface. In this study, a self-assembled molecular (SAM) of trimethoxy(3,3,3-trifluoropropyl)silane (TFTPS) is constructed on a traditional Bi-based electrocatalyst to enhance its catalytic efficiency. The modified catalyst delivers a high current density of 800 mA cm-2 and maintains a formate Faradaic efficiency of up to 95% across a wide pH range. Notably, it also exhibits an excellent long-term durability of 250 h in a membrane electrode assembly system. Density functional theory calculations and classical molecular dynamics simulations reveal that this hydrophobic SAM possesses three key functions: (i) it maintains interfacial hydrophobicity to reduce H+ activity and prevent electrode flooding; (ii) it stabilizes a relatively higher oxidation state on the catalyst surface, thereby enhancing *OCHO adsorption; and (iii) it facilitates CO2 mass transfer and local enrichment. These findings are further supported by in situ x-ray diffraction and spectroscopic measurements. Overall, this study proposes a molecular self-assembly strategy for optimizing tri-phase interfaces in electrocatalysis, which could drive advances in energy conversion technologies.