Boosting Fuel Cell Performance with Accessible Carbon Mesopores

We present that heavy use of scarce Pt in the electrodes poses a barrier to the application of proton exchange membrane fuel cells (PEMFCs) for transportation. Although some automakers can now commercialize fuel cell electric vehicles (FCEVs) with as little as 30 g of Pt, this is still substantially more than what incumbent internal combustion engine vehicles use (2-8 g of precious metals). A long-term target of <5 g of Pt-group metals per vehicle is probably needed to be sustainable. Since W. R. Grove’s invention of the fuel cell in 1839, most breakthroughs in fuel cell performance have been associated with an increase in the so-called three-phase interface—the interface where the reactant gas meets electrons in the solid phase and protons in the electrolyte phase. Pt is made into nanoparticles and supported on carbon black to increase the mass-specific Pt surface area and to secure large pores for reactant oxygen gas to access Pt. Solid electrolyte such as the perfluorosulfonic acid (PFSA) ionomer is blended with the catalyst to carry protons to the Pt surface. Lastly, despite a long history of maximizing the three-phase interfacial area, one must realize that an optimized three-phase interface does not equal a maximum Pt/ionomer interface area.