Hydroxyl-engineered Ag nanoparticles achieves almost 100 % faradaic efficiency in electrocatalytic CO₂ reduction to...

Electrocatalytic CO₂ reduction (ECO₂R) to CO provides a promising strategy for mitigating atmospheric CO₂ levels in the atmosphere while generating value-added chemical feedstocks for industrial applications. However, the widespread implementation of ECO₂R remains constrained by insufficient activity and Faradaic selectivity of current catalysts under practical operating conditions. We here develop a hybrid material of Ag nanoparticles embedded in cyclodextrin (AgNPs-CD) with abundant surface hydroxyl groups, which functions as an efficient catalyst for ECO₂R to CO, delivering both high activity and excellent selectivity. The AgNPs-CD achieves an exceptional CO Faradaic efficiency (FE_CO) of 97.6 % at an ultralow potential of -0.4 V vs. RHE and sustains high FE_CO values ranging from 93.5 % to 99.8 % over a broad potential window (-0.4 to -1.0 V vs. RHE), while simultaneously affording a high CO partial current density (J_CO) exceeding 200 mA cm^-2. In situ electrochemical spectroscopy and theoretical calculations reveal that AgNPs-CD stabilizes *COOH with a lower Gibbs free energy and inhabits the hydrogen evolution reaction (HER) with high energy barrier, making high activity and high selectivity toward CO₂ to CO conversion. This work can not only provide an efficient strategy to enhance the performance of ECO₂R to CO but also shed light on the design and development of novel electrocatalysts with low overpotential and high current density.