Breaking the Limit of Size-Dependent CO₂RR Selectivity in Silver Nanoparticle Electrocatalysts through Electronic Metal-Carbon Interactions

We demonstrate that electronic metal-support interactions (EMSIs) between silver and carbon can dramatically improve the CO2 reduction reaction (CO2RR) performance of the small Ag nanoparticles. Ag-C EMSIs were created by ultrahigh vacuum deposition of Ag onto defect-containing (sputtered) highly oriented pyrolytic graphite, and calculations predicted that 1.02 e was transferred from Ag to carbon, which stabilized the *COOH reaction intermediate, lowered the potential-limiting CO2RR step, and improved the predicted CO2-to-CO performance. Experimentally, we identified a scaling relationship between particle size and the relative Ag-C EMSI strength, which improved the CO2-to-CO Faradaic efficiency of sub-2 nm Ag particles from 2 to similar to 100% and increased the CO turnover frequency similar to 15-fold compared with similarly sized Ag particles grown in the absence of Ag-C EMSIs. We extended this concept to grow sub-2 nm Ag electrocatalysts on commonly used carbon black catalyst supports and showed that the interaction with support defects could sustain CO selectivity comparable to larger particles, suggesting an approach for tailoring CO2RR electrocatalyst performance.