CoPc- and CoPcF16-Modified Ag Nanoparticles as Novel Catalysts with Tunable Oxygen Reduction Activity in Alkaline Media

Abstract

A new class of non-Pt “hybrid” catalysts is reported that is intended as a lower cost alternative that meets the performance and durability requirements of the oxygen cathode in fuel cells with alkaline electrolytes. These novel hybrid catalysts are cobalt (Co) phthalocyanine on silver (Ag) nanoparticles on a carbon (C) support. For O2 reduction, a catalyst with cobalt phthalocyanine (CoPc) on Ag nanoparticles on carbon (CoPc@Ag/C) or the fully fluorinated cobalt phthalocyanine (CoPcF16) on Ag nanoparticles on carbon (CoPcF16@Ag/C) showed lower overpotentials and higher rate constants at a given potential than did CoPc and CoPcF16 on carbon (CoPc/C and CoPcF16/C) and Ag nanoparticles on carbon (Ag/C). The oxygen reduction reaction (ORR) activity of the cobalt-phthalocyanine-modified Ag nanocatalysts is tuned by adjusting the composition of the metalated phthalocyanine molecules adsorbed on Ag. X-ray photoelectron spectroscopy (XPS) and electrochemical characterizations indicate that the ORR on these new c...