Activity and Durability of a Membrane Electrode Assembly Fabricated with Supportless Pt Hollow Spheres for Polymer Electrolyte Fuel Cells

Extensive studies on the supportless Pt or Pt alloy catalysts with controlled morphology have led to significant enhancement in catalytic activity as well as in durability for polymer electrolyte fuel cells (PEFCs). However, the supportless Pt still shows lower performance than the state of the art Pt/C when the catalysts were fabricated to a membrane electrode assembly (MEA) due to not efficient catalyst layer architecture of the supportless Pt catalysts. In order to achieve high MEA performance, the catalyst should be designed in terms of catalyst layer architecture as well as oxygen reduction reaction (ORR) activity. Here we report supportless Pt hollow sphere (PtHS) catalyst that is composed of assembled Pt nanoparticle shell and hollowed center for 3-dimensional cathode catalyst layer architecture. The PtHS is expected to be efficient for high MEA performance mainly due the following aspects: (i) PtHS with submicron size will form large mean pore size and high pore volume in the catalyst layers, which will be beneficial in preventing water flooding and in improving water management for facile oxygen transport; (ii) hollow structure of PtHS will be used as liquid water reservoir at high currents and consequently enhance oxygen transport; (iii) thin-layered PtHS shell composed of assembled Pt nanoparticles would lead to large Pt surface area and high Pt utilization; (iv) assembled supportless Pt nanoparticles will increase the catalyst durability by preventing the aggregation and sintering of Pt nanoparticles. These potential merits of PtHS in terms of activity and durability will be demonstrated in a half-cell as well as in a single cell with the PtHS-based MEAs. The activity and stability of PtHS-based MEAs will be compared with the commercial Pt/C-based MEAs in a single fuel cell.