Controlling Nanoparticle Interconnectivity in Thin-Film Platinum Catalyst Layers

The optimization of conventional hydrogen fuel cell catalyst layers suffers from a poor understanding of their composite nanostructure during both initial preparation and its evolution during use. We demonstrate how highly active, ultralow loading platinum (Pt) catalyst layers can be fabricated in a single, solution-processable step using electroless deposition. Growing Pt nanoparticles directly in the surface of a polyelectrolyte Nafion membrane yields a mechanically robust film with tunable optical reflectance and electronic conductivity. Small changes in the polymer hydration and Pt film thickness critically modulate nanoparticle interconnectivity near the percolation threshold. Conductive atomic force microscopy (AFM) and electron microscopy reveal how the film's dynamic nanoscale morphology allows control over bulk electrochemical and optical properties. Well-defined composition and structure make these layers an experimentally accessible model system for studying thin-film electrocatalyst architectures.