Silver-based catalysts are attractive for electroreduction of CO2 to CO. To understand the electrocatalyst properties, a good control over the nanoparticle size is necessary. Herein, we report a strategy to synthesize highly dispersed, ligand-free silver Ag nanoparticles supported on carbon. We demonstrate that the heat treatment atmosphere and carbon surface chemistry are crucial to control the Ag particle size in the 10–30 nm range. Even at low silver loadings (0.099 m2Ag m−2), Ag nanoparticles outperforms the bulk silver at low overpotentials, leading to a 23.5 % CO Faradaic efficiency at −1.2 V vs RHE. The Ag weight-based activity of the catalysts scales with the inverse particle size, while the Ag surface-specific activity is independent of the particle size in this range. The supported silver nanoparticles can produce a H2 to CO ratio of 2.9 to 1, interesting for further exploration of this type of catalysts for syngas synthesis
