Impact of ionomer structuration on the performance of bio-inspired noble-metal-free fuel cell anodes

Summary Molecular-engineered bio-inspired catalysts hold promise for the next generation of proton-exchange membrane fuel cells (PEMFCs). Yet, their implementation in catalytic layers with Nafion ionomer faces nanocomposite formulation issues. Here, we use various DuBois nickel catalysts immobilized on carbon nanotubes to exemplify how self-assembly at the mesoscale affects H2 oxidation anode performance. We exploited the reversible activity of these catalysts together with potential-step chronoamperometry to locally produce H2 and probe mass transport within the catalytic layer. Small-angle neutron scattering studies serve to build a model describing how the surface functionalization drives the structuration of the ionomer and affects the diffusion of protons and gas from and to catalytic centers. This study thus demonstrates that implementation of unconventional catalysts in catalytic layers requires the redesign of the whole system of materials. On the basis of such information, catalytic layer formulation was optimized, allowing order-of-magnitude performance enhancement of noble-metal-free PEMFCs.