Bottom-Up Fabrication of Oxygen Reduction Electrodes with Atomic Layer Deposition for High-Power-Density PEMFCs

As the platinum (Pt) loading in proton exchange membrane fuel cell cathodes is driven down to reduce costs, catalyst utilization becomes increasingly important. Here, we report an atomic layer deposition-facilitated electrode fabrication technique designed to improve the catalyst-ionomer interface. The ionomer solvent environment and carbon support nanoporosity are studied independently, and it is found that the combination of an agglomerated ionomer dispersion and a mesoporous support gives access to a high catalytic activity (mass activity [MA] = 0.31 A/mgPt with pure Pt) that can be maintained at high current densities. We hypothesize that the formulation results in Pt sufficiently withdrawn from the ionomer such that poisoning and transport losses are reduced. When paired with a low-resistance dispersion-cast membrane, a 0.1-mgPt/cm2 cathode can deliver a 0.65-V power density of 1.0 W/cm2 at 150 kPa and 80°C. The assembly also demonstrates impressive durability, losing only 33 mV after 30,000 cycles.