Probing Impact of Support Pore Diameter on Three-phase Interfaces of Pt/C Catalysts by Molecular Dynamic Simulation

Investigating how the size of carbon support pores influences the three-phase interface of platinum (Pt) particles in fuel cells is essential for enhancing catalyst utilization. This study employed molecular dynamics simulations and density functional theory calculation to examine the effects of mesoporous carbon support size, specifically its pore diameter, on Nafion ionomer distribution, as well as on proton and gas/liquid transport channels, and the utilization of Pt active sites. The findings show that when Pt particles are located within the pores of carbon support (Pt/PC), there is a significant enhancement in the spatial distribution of Nafion ionomer, along with a reduction in encapsulation around the Pt particles, compared to when Pt particles are positioned on the surface or in excessively large pores of the carbon support. While increasing pore diameter improves the construction of proton transport channels formed by sulfonate groups of Nafion ionomer and water molecules, it also raises the risk of obstructing oxygen diffusion. To achieve maximum Pt utilization and exchange current density, it is essential to balance the proton and gas/liquid transport channels. Among the models investigated, the Pt/PC-8 nm system demonstrates the highest Pt utilization. This work offers valuable insights for designing carbon support materials to optimize three-phase interfaces in the catalytic layer of fuel cells.