Tin-nitrogen/carbon for superior oxygen reduction reaction at fuel cell cathode

This work reports on the synthesis of tin-nitrogen/carbon (Sn–N/C) catalysts suitable for the electroreduction of molecular oxygen at the cathode of proton exchange membrane fuel cells. The catalysts were synthesized through a simple pyrolysis process of folic acid as the carbon and nitrogen source, tin chloride as a tin source and Vulcan carbon as the substrate. The synthesized catalyst exhibited excellent oxygen reduction activity with a half wave potential of 0.82 V and a mass activity of 15.5 mA mg−1. Successful application at the cathode of a self-breathing fuel cell further confirmed the superior performance of this catalyst leading to a power density of 29.4 mW cm−2. This is very comparable to the reference platinum/Vulcan carbon catalyst (28.4 mW cm−2). In addition, this Sn–N/C catalyst showed good stability under accelerated stress tests with only a 12% decrease in fuel cell performance after 10,000 cycles. The superior performance was assumed to be due to the presence of both metal-nitrogen and nitrogen-carbon active sites, which facilitate the four-electron path of the oxygen reduction reaction.