Highly active and selective Ag/C catalysts for CO2 electrolysis to CO using 4-aminothiophenol as anchoring agent

Carbon supported silver nanoparticles (Ag/C) have the potential to reduce the precious metal content in the catalyst layer of carbon dioxide (CO 2 ) electrolyzers producing carbon monoxide (CO), while enhancing the electrochemical performance at the same time. Typically, molecular linkers (e.g. cysteamine) are used to attach the Ag nanoparticles (Ag NPs) to the carbon support. In this study, 4-aminothiophenol (4-ATP) is used for the first time as an alternative anchoring agent, yielding evenly dispersed Ag nanoparticles with an average particle size of 2 nm. Using this linker a current density of 1 A cm −2 was achieved with faradaic efficiency for CO of 85 % at 3.3 V. These results were obtained with a low Ag loading of 0.26 mg Ag cm −2 , yielding a turnover frequency of 9.6 s −1 . The catalyst demonstrated high stability during long-term measurements exceeding 200 hours at 500 mA cm −2 . The faradaic efficiencies for CO remained consistently around 80 % at 3.1 V, with a cell voltage degradation rate of 1.5 mV h −1 . This makes thiol-based linkers promising candidates for surface modification to promote durable, efficient and selective electrocatalysts for CO 2 electrolysis to CO. • Aromatic 4 aminothiophenol (4-ATP) was used to fix 2 nm Ag nanoparticles on Vulcan black and bond formation was confirmed through XPS analysis. • The obtained Ag/C catalyst was used in a zero-gap CO₂ electrolyzer for CO generation outperforming Ag/Cs with aliphatic anchoring agents and pure Ag catalysts. • The catalyst achieved current densities up to 1 A cm⁻² with an FE CO > 85 % at full cell potentials below 3.4 V. • In long-term measurements exceeding 200 hours at application relevant current densities of 500 mA cm −2 , the FE CO remained consistently around 80 % at 3.1 V, with a cell voltage degradation rate of 1.5 mV h −1 .