Ligand-Free Silver Nanoparticles for CO2 Electrocatalytic Reduction to CO

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 m(Ag)(2) 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 H-2 to CO ratio of 2.9 to 1, interesting for further exploration of this type of catalysts for syngas synthesis.