Designing Natural Cell-Inspired Heme-Spurred Membrane Electrode Assembly for Fuel Cells.

Developing highly efficient and durable membrane electrode assemblies (MEAs) is imperative for the widespread implementation of proton exchange membrane fuel cells (PEMFCs). However, the poor mass transfer efficiency and sluggish oxygen reduction reaction (ORR) kinetics have significantly suppressed the power density and longevity of platinum (Pt)-based MEA in PEMFCs, particularly when using an ultralow Pt loading. Inspired by the functional principles of hemoglobin in red blood cells, we present a Heme-cofactor strategy to create a "respiratory proton-transfer chain" for PEMFCs. This strategy can efficiently spur the catalytic activity of Pt while enhancing the mass transfer efficiency of MEAs, in which the multifunctional Heme featuring carboxyl and Fe2+ groups can accelerate the proton and oxygen transport as well as boost the ORR kinetics. As a result, by integrating Heme with typical Pt catalysts (i.e., commercial Pt/C, commercial Pt3Co/C, and homemade PtCo), the peak power density (PPD) and mass activity (MA) of Heme-spurred Pt-type MEAs can be dramatically enhanced by 50 to 109%, respectively. Particularly, with a low Pt loading of 0.1 mgPt cm-2, the Heme-spurred PtCo-based MEA achieves record PPDs of 3.8 W cm-2 (H2-O2) and 1.9 W cm-2 (H2-air), significantly surpassing the previous PPD records set by state-of-the-art MEAs. Meanwhile, our developed Heme-spurred MEA can even be run stably at 1.5 A cm-2 for over 50 days (1250 h) with 93% MA retention. These results underscore the viability of this universal and efficient Heme-cofactor strategy for practical fuel cell applications.