Hydrogen bond stabilized *CO intermediate enables CO₂ electroreduction to multi-electron products on silver catalysts.

Abstract

Silver is an extensively investigated electrode material for electrochemical CO₂ reduction owing to its high electrical conductivity and structural stability. However, a key limitation of silver catalysts is their weak adsorption of the *CO intermediate. This intrinsic constraint restricts the reaction primarily to two-electron pathways, hindering the formation of multi-electron products. Here we demonstrate that surface molecular modification can address this limitation. By anchoring bromothymol blue molecules onto the silver surface, we engineer a localized hydrogen-bonding network that stabilizes *CO intermediates via O···H-O interactions, prolonging their surface residence time. In situ spectroscopy and theoretical simulations reveal that this local microenvironment thermodynamically stabilizes *CO against desorption while kinetically facilitating its subsequent hydrogenation and C-C coupling. Consequently, the retained *CO undergoes deeper reduction pathways, generating CH₄, C₂H₄, C₂H₅OH, and CH₃COOH. At a current density of 400 mA cm^-2, the Faradaic efficiency for multi-electron products reaches 24.2%. This work shifts the design paradigm from metal-centric electronic tuning to local microenvironment engineering, offering an alternative strategy for enabling multi-electron transfer on non-copper catalysts.