Revealing the structural and transport properties in the narrow channels of porous carbon for fuel cells

Porous carbon is a promising catalyst support due to its high specific surface area and suppressing catalyst poisoning by ionomer. However, the underlying transport phenomena in narrow channels of porous carbon is still unclear. We employ molecular dynamics (MD) simulations to reveal the structural and transport properties in the narrow pore and crack channels. The results show that the smaller narrow channel (<6 nm) can effectively prevent the PFSA chains from penetrating the channel and covering the catalyst inside the porous carbon. The narrow channel is accessible for water, proton, and oxygen. The PFSA chains prefer to aggregate along the hydrophobic wall of narrow channel, while the water channel is formed in the middle of narrow channel. The protons migrate via the water channel that is more easily formed in a wider channel and at a higher hydration. The oxygen molecules preferentially migrate along the wall of narrow channel. The transport resistances of protons and oxygen molecules will decrease as the channel width increases. The findings demonstrate that the opening width of narrow channels needs to be optimized by balancing the blockage effect on PFSA chains and the transport resistances of protons and oxygen.