3D-structured electrocatalysts for improved mass-transfer in proton-exchange membrane fuel cell cathodes

High-performance proton-exchange membrane fuel cells (PEMFCs) are required to decarbonize the industry and transportation sectors. Implementing new technologies in PEMFCs may enable to overcome their technological barriers, notably their short lifespan and insufficient specific power per mass of costly and poorly-available platinum-based electrocatalysts. Pt-based electrocatalysts, the present state-of-the-art, must be more efficiently utilized in the PEMFC electrodes and in particular the cathode. This review presents that, despite recent successes, conventional randomly-organized Pt/carbon-black plus ionomer active layers cannot optimize the complex interplay between Pt electrocatalytic activity and proton/oxygen gas/liquid water mass-transfer within their structure. Numeric models clearly show that oriented electrodes or 3D-structured electrodes should better utilize the Pt electrocatalyst, thanks to more efficient mass-transfer to/from the catalytic sites in operation. The recent achievements in these exciting technologies will be recalled, and their advantages and drawbacks summarized, so to propose a strategy for future developments towards their implementation in practical PEMFCs.