Derived MOF/Ag Electrocatalysts for Selective and Stable CO Production during Acidic CO ₂ Electroreduction

Metal–organic frameworks (MOFs) and their derived catalysts are attractive for carbon dioxide (CO2) electroreduction to carbon monoxide (CO) but face challenges, including salt precipitation in neutral/alkaline electrolytes and poor selectivity in acidic media. Herein, we conducted in situ electrochemical pretreatment on the Ag MOF of Ag5(pyridine-3,5-dicarboxylic acid)2(OH) (AgPyDC) to form derived AgPyDC/Ag electrocatalysts with heterostructures between Ag nanoparticles (NPs) and residual MOFs, which prevent salt precipitation and enhance catalytic activity in acidic CO2 electroreduction. AgPyDC/Ag electrocatalysts exhibit a CO Faradaic efficiency (FE) of 91% and long-term stability over 50 h at pH = 3, whereas the CO FE of Ag NPs is only 38%, which indicates that such AgPyDC/Ag heterostructures can greatly enhance selectivity and stability. X-ray photoelectron spectroscopy reveals that such AgPyDC/Ag heterostructures exhibit a more electron-rich Ag state than Ag NPs. In situ Raman spectroscopy reveals that such AgPyDC/Ag heterostructures facilitate CO2 activation, while the interfacial water structure highlights a stable interfacial K+ concentration that underpins efficient CO production. This work not only provides a cost-effective pathway toward acidic CO2 electroreduction but also offers mechanistic insights into MOF-derived structures that enhance catalytic activity, guiding advanced catalyst design.