Oxygen Transport Routes in Ionomer Film on Polyhedral Platinum Nanoparticles

Abstract

Understanding the O 2 permeation phenomenon in the ionomer thin film on platinum (Pt) nanoparticles is vital to improve the electrocatalyst performance of proton exchange membrane fuel cells at a low Pt loading. In this study, the ionomer film structure, O 2 density distribution, transport fluxes, and permeation routes are investigated for carbon-supported polyhedral Pt nanoparticles (cube and tetrahedron) in the facet, edge, and corner regions. The molecular dynamic simulation takes into account the molecular interactions among the ionomer, Pt nanoparticles, carbon support, and O 2 molecules. The results show that a dense ionomer ultrathin layer with a tight arrangement of perfluorosulfonic acid is present on the Pt facets (namely region A). In the ionomer near the Pt edges and corners (namely region B), the structure is less dense due to the weaker Pt attraction, resulting in a higher O 2 density than that in region A. O 2 fluxes in the different regions show that approximately 90% of O 2 molecules reach the Pt cube and tetrahedron nanoparticles via their upper corner and edge regions. In the vicinity of Pt nanoparticles, O 2 permeation routes are inferred to penetrating region B to the Pt upper corners or edges instead of region A to the Pt facets.

PEM Fuel cell and electrolysis cell technologies and hydrogen infrastructure development – a review

“…Recently, a poly(2,3,5,6tetrafluorostyrene-4-phosphonic acid) membrane that is free The symbol colors (a and b) match the bead colors in the different locations of Pt nanoparticles; and (e) schematics of O 2 permeation routes. 176 Energy & Environmental Science Review of anhydride formation, was reported; this membrane maintains its ionic conductivity above 200 1C and achieves peak powers of 1130 and 1740 mW cm À2 at 160 1C and 240 1C, respectively, using O 2 reactant. 181 Another approach is to use thin PEMs, which reduces ionic resistance.…”

“…Fig. 16 The number of O 2 molecules reaching Pt nanoparticles via the ionomer film (a and b) and portions of O 2 fluxes at different locations (c and d).The symbol colors (a and b) match the bead colors in the different locations of Pt nanoparticles; and (e) schematics of O 2 permeation routes 176. …”

Recent Insights on Catalyst Layers for Anion Exchange Membrane Fuel Cells

“…Several molecular dynamics (MD) revealed that ionomer tends to form a thin layer on the surface of catalyst due to specific interactions. [169,170] The group of Jang [171] calculated the binding energies of Nafion with Pt nanoparticles using quantum mechanical DFT and molecular dynamics. It is inferred that sulfonate groups tend to be chemisorbed while CF 3 CF 3 and CF 3 OCF 3 tend to be physisorbed.…”

Interlink among catalyst loading, transport and performance of proton exchange membrane fuel cells: a pore-scale study

“…13 Based on the literature, CL modeling methods can be categorized into thin film models, 14 homogeneous models, 15 agglomerate models, 16 pore-scale models 17 and molecular dynamics models. 18 With a focus on the structural effect on performance, the pore-scale modeling method has become a trending method to resolve the physicochemical phenomena in the complex microstructure. 19–22 The mesoscale numerical tool, namely, the lattice Boltzmann method (LBM), is mostly applied to model coupled transport processes due to its advantages in implementing boundary conditions and parallel computing.…”