Carbon-caged palladium catalysts supported on carbon nanofibers for proton exchange membrane fuel cells

The development of low-cost catalysts for the oxygen reduction reaction is an important step for the commercialization of proton-exchange membrane fuel cells. Pd is a robust catalytic material for this reaction and is considered as an alternative to Pt due to its similarity with Pt. However, since Pd is oxidized at a lower positive potential than Pt, it is less active and less stable than Pt in an oxygen reduction reaction. We developed a simple synthesis route for N-doped carbon-caged Pd catalysts supported on carbon nanofibers using Pd-polyaniline composites. Oxidative polymerization of aniline spontaneously produced Pd-polyaniline composites with the reduction of Pd ions. The subsequent heat treatment of Pd-polyaniline composites produced N-doped carbon-caged Pd catalysts, in which the polyaniline served as the source of the N-doped carbon cage. The catalytic activity and stability of the synthesized catalyst were dependent on the heat-treatment temperature and the synthesis method. The optimized catalyst heat-treated at 500 degrees C (Pd@NC/CNF500 (NDA, US)), which was synthesized with non distilled aniline under ultrasound irradiation, exhibited higher catalytic activity and stability in oxygen reduction reaction than general Pd catalysts reported in literature. Pd@NC/CNF500 (NDA, US) showed high performance even in the unit cell test. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.