Ag/C composite catalysts derived from spray pyrolysis for efficient electrochemical CO2 reduction

In this study, Ag/C composite catalysts with different weight ratios (20, 50, and 75 wt% Ag) were synthesized by spray pyrolysis to improve the performance of electrochemical CO2 reduction for CO production. Among the electrocatalysts tested, the Ag75/C composite catalyst (75 wt% of Ag nanoparticles dispersed in carbon black support) showed the highest electrochemical CO2 reduction performance, along with high stability that surpassed that of pure Ag particles. Above all, this is because Ag nanoparticles were dispersed on the surface of (and inside) the carbon black support. This enlarged the Ag surface area, thereby increasing the number of electrochemical CO2 reduction sites. Additionally, the carbon black support has a hierarchically porous structure that improved the transport of the catholyte, reactant, and products, enabling enhanced electrochemical CO2 reduction to CO. Furthermore, the use of carbon black support in the Ag/C composite catalysts allows the binder to bind more carbon microspheres than Ag nanoparticles, reducing the Ag surface area covered by the binder in comparison with that for pure Ag particles. Thus, the charge transfer resistance of a Ag/C composite catalyst was much lower than that of pure Ag particles due to the improved interconnection, contact, and number of electrochemical reaction sites provided by the combination of carbon black support and Ag nanoparticles. All of these interpretations imply that carbon black is an appropriate support able to play a key role in improving CO productivity via electrochemical CO2 reduction.