# Pore-Scale Investigations into Gradient Carbon Microstructures for Enhanced Mass Transport in PEM Fuel Cell Catalyst Layers

## TL;DR

This study explores how varying carbon sphere sizes in fuel cell catalyst layers improves oxygen transport and performance using simulations.

## Contribution

A novel framework for optimizing carbon sphere diameter distributions in PEMFC catalyst layers to enhance mass transport and electrochemical efficiency.

## Key findings

- Gradient carbon sphere designs modulate pore size distribution and oxygen diffusion in catalyst layers.
- L-M-S three-layered gradient design increases current density by 15.4% and reduces concentration gradients.
- Larger spheres near the gas diffusion layer improve pore connectivity, while smaller spheres near the membrane enhance reaction sites.

## Abstract

This study investigates the impact of non-uniform carbon sphere diameter distributions on the structural and electrochemical performance of catalyst layers (CLs) in proton exchange membrane fuel cells (PEMFCs), utilizing the lattice Boltzmann method (LBM) for detailed simulations. The impact of carbon sphere diameter range and gradient distribution on oxygen transport, electrochemical reactivity, and catalyst layer morphology was investigated. The results show that gradient designs of carbon sphere diameters effectively modulate pore size distribution, electrochemically active surface area, and oxygen diffusion pathways within the CL. Specifically, placing larger carbon spheres near the gas diffusion layer improves pore connectivity and oxygen transport, while smaller spheres near the membrane enhance the availability of reaction sites. The three-layered gradient design, particularly the L-M-S configuration, demonstrated superior oxygen distribution, reduced concentration gradients, and increased current density by 15.4%. These findings underline the importance of optimizing carbon sphere diameter distributions for enhancing CL performance. This study offers a novel framework for designing catalyst layers with improved mass transport and electrochemical efficiency, providing significant insights for the future development of high-performance PEMFCs.