Relationship between Electroless Pt Nanoparticle Growth and Interconnectivity at the Membrane Interface: Implications for Fuel Cell Applications

Growth of Pt nanoparticles by electroless deposition of Pt ions in a cation exchange membrane (Nafion) has been characterized and modeled with respect to the interconnectivity of the nanoparticles. With the nonequilibrium impregnation-reduction method, Pt nanoparticles formed a thin layer (≤200 nm) with metal loadings ranging from 10 to 70 μgPt cm–2. The growth of the Pt nanoparticles is influenced by a combination of grain growth and coalescence and shows a power law dependence on the Pt grain size for the range of Pt loadings examined. The platinized membranes were carefully characterized by a number of analytical techniques to obtain correlations between Pt nanoparticle loading, grain size, and interconnectivity. The variation of electrochemically active surface area (ECSA) and Pt crystallite size with the impregnated Pt content is presented. This low loading, high density platinized membrane can be used as an extended catalyst layer at the membrane interface to improve fuel cell operational flexibility, especially under dry conditions. In addition, simple relationships between the ECSA, Pt utilization, grain dimension, and interconnectivity are shown