Supportless silver nanowires as oxygen reduction reaction catalysts for hydroxide-exchange membrane fuel cells

Silver nanowires (AgNWs) and nanoparticles (AgNPs) have been synthesized to facilitate hydroxide-exchange membrane fuel cell development and commercialization. AgNWs and AgNPs with variable diameters (25-60 nm AgNWs, 2.4-30 nm AgNPs) have been studied with rotating-disk electrode experiments to examine the impact of size and morphology on the oxygen reduction reaction (ORR). Although a detrimental particle size effect is observed, AgNWs exceed the specific activity of bulk polycrystalline Ag. AgNWs with a diameter of 25 nm further exceed the ORR specific and mass activity of 2.4 nm AgNPs 5.3 times and by 16 %, respectively. Rotating ring-disk electrode testing demonstrates minimal peroxide formation on AgNWs; peroxide production increases with the use of AgNPs by as much as an order of magnitude and further increases with particle size reduction. Silver catalysts demonstrate alcohol tolerance for ORR, illustrating the benefit of silver and AgNWs as catalysts in hydroxide and alcohol hydroxide-based fuel cells.