Size-Controlled Synthesis of L10-CoPt Intermetallic Fuel Cell Catalysts on Nitrogen-Doped Mesoporous Graphitized Carbon Support

Abstract

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). However, after subjecting to a widely used postsynthesis annealing treatment, the particle size of intermetallic catalysts inevitably increases, leading to a poor performance in practical fuel cell application. In this work, ordered L10-CoPt intermetallic catalyst of small particle size was prepared through using nitrogen-doped mesoporous graphitized carbon (NMGC) support. The porous feature and nitrogen doping of NMGC support immobilized CoPt particles and prevented sintering during annealing treatment. These small and ordered L10-CoPt nanoparticles exhibit outstanding ORR activity (~ 1.18 A/mgPt) and superior high current density in fuel cell testing. Moreover, this L10-CoPt/NMGC catalyst performs remarkably enhanced stability in comparison with L10-CoPt/high surface area carbon (HSC) counterpart and commercial Pt/C catalyst, surpassing the DOE 2020 target. The enhancement in catalyst durability can be attributed to strong particles-support interaction via nitrogen heteroatoms and the strengthened p bonding. To better understand the support effect on particle growth, L10-CoPt particles on NMGC with different porosity/graphitization were prepared and their fuel cell performances were systematically studied. This study demonstrates an effective strategy to control the particle size of intermetallic catalysts with using NMGC support, which achieves excellent practical fuel cell performance.