Nanocage Sops Filled Cathode Catalytic Layer with Enhanced Pt Utilization and Mass Transfer for High-Performance Fuel Cell

Abstract

Reducing the overpotential loss caused by water flooding operated at high current density in fuel cells is highly desired yet challenging, hence the improvement of mass transport in cathode catalytic layer (CCL) without sacrificing oxygen reduction reaction (ORR) activity is crucial. We regulate the three-phase interface structure by optimizing the deposition of ionomers though incorporating sulfonated octaphenyl polyhedral oligomeric silsesquioxane (SOPS) nanocage into catalyst ink. The hollow hexahedron with approximately 0.48 nanometers diameter, hydrophobic phenyl and grafted sulfonate groups promote oxygen permeation, water drainage timely and proton transmission accessible. The peak power density of the fuel cell added 5%wt SOPS achieves 1.22 W cm-2and increases 25%, the electrochemical surface area reaches 1.3 times and the Warburg admittance (YoWarburg) increases 1.6-fold at 2000mA cm-2 compared to no addition. The molecular dynamics simulation calculations suggest that the Nafion coverage of Pt surface decreases 15% because of the SOPS, leading to increase ORR activity sites. And the diffusion coefficient of oxygen and water is also increased by 20% and 36%. This strategy is scalable and would be improvement the performance of different commercial catalysts.

Keywords: PEMFC cathode catalyst layer, three-phase interface, SOPS, high current density, low overvoltage loss