Fully Ordered Pt3Co Intermetallic Nanoparticles Derived from MOFs for Oxygen Reduction in PEMFCS

Abstract

Proton exchange membrane fuel cells (PEMFCs) are considered to be a promising power source for electric vehicles and stationary residential applications. However, current PEMFCs have several problems that need to be overcome including high cost, insufficient power density, and poor performance durability. Current Pt-based cathodes for the oxygen reduction reaction (ORR) are primarily responsible for these issues. Development of advanced Pt-based catalysts are crucial for solving these problems in order for large-scale application of PEMFCs to be feasible. Recently, highly ordered PtM alloy catalysts have exhibited significantly enhanced activity and stability for the ORR in PEMFCs, which have attracted substantial attention. Based on our ongoing research projects [1-3], in this presentation, we introduced our recent progress to develop low-PGM catalysts with emphasis on the innovative synthesis methods of using pre-doped transition metals such as Co or Ni into metal–organic-framework (MOF)-derived carbon as the sources to prepare highly ordered PtM catalysts. As an example, ordered Pt3Co intermetallic nanoparticles through a facile thermal treatment of Pt nanoparticles supported on Co-doped MOF-derived carbon. Atomically dispersed Co sites are originally embedded into MOF-derived carbon. Then we can accurately control the diffusion of Co into Pt crystals and form ordered Pt3Co structures. It is very crucial for the formation of the ordered Pt3Co to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. The optimal Pt3Co nanoparticle catalyst has achieved significantly enhanced activity and stability. The highly ordered intermetallic structure was retained after the accelerated stress tests made evident by atomic-scale elemental mapping. Fuel cell tests further verified the high intrinsic activity of the ordered Pt3Co catalysts. The new synthesis approach provides an effective strategy to develop active and stable Pt alloy catalysts by leveraging the unique properties of MOFs such as 3D structures, high surface areas, and controlled nitrogen and transition metal dopings. This concept also provides a solution to take advantages of current atomically dispersed PGM-free catalyst to develop high-performance low-PGM cathode catalysts.