Micropillar-patterned electrodes to enhance mass transfer in low Pt-loaded fuel cells

The practical application of fuel cell vehicles is hindered by poor performance and durability of proton exchange membrane fuel cells (PEMFCs), especially at low Pt loading and low relative humidity conditions, owing to limited proton transport properties and electrochemical reaction surface areas of conventional electrode design. This study proposes a patterned design with ordered ionomer micropillars as an alternative electrode structure to enhance the performance and durability of PEMFCs with low Pt loading (0.1  mg cm^-2) across a wide range of humidities. Compared to conventional electrodes, the patterned electrodes achieved up to 29% peak power density improvement under low-humidity (50% relative humidity) conditions. Pore-scale multiphysics modeling demonstrated that the ionomer micropillars inside the patterned electrodes transform the distorted transport pathways of conventional, randomly distributed catalyst layers into ordered, short-range channels for rapid oxygen and proton delivery, which significantly enhances the oxygen reduction reaction rate. Moreover, the patterned electrodes exhibited improved durability, showing lower performance loss compared to conventional electrodes after accelerated stress testing across a wide range of humidities. Strategic redesign of the ionomer micropillars demonstrated that the H1.8W0.38 electrode (with a micropillar height of 1.8  μm and width of 0.38  μm), with its increased penetration depth and appropriately adjusted width, achieves optimal performance by minimizing oxygen and proton transport resistances by 6% and 14%, respectively, compared to the pre-optimization (H1.5W0.38) electrode, under low-humidity (50% relative humidity) conditions. The proposed patterned electrode architecture offers a promising approach for advancing the development of high-performance, cost-effective, and durable fuel cells.