COF-assisted construction of steric mass-charge channels to boost activity for high-performance fuel cells.

The two-dimensional lamellar materials disperse platinum sites and minimize noble-metal usage for fuel cells, while mass transport resistance at the stacked layers spurs device failure with a significant performance decline in membrane electrode assembly (MEA). Herein, we implant porous and rigid sulfonated covalent organic frameworks (COF) into the graphene-based catalytic layer for the construction of steric mass-charge channels, which highly facilitates the activity of oxygen reduction reactions in both the rotating disk electrode (RDE) measurements and MEA device tests. Specifically, the normalized mass activity is remarkably boosted by 3.7 times to 1.56 A mgpt-1 after additions of suitable COF modifications in the RDE tests. Especially, an excellent maximum power density of 1.015 W cm-2 is realized on the MEA in H2/Air condition, representing a 22% improvement through such constructions of steric mass-charge channels. Meanwhile, the open-circuit voltage of fuel cells demonstrates only 0.8% reductions after 10,000 cycles of stability tests. We further extended such methodology of constructing mass-charge channels to granular PtCo and commercial Pt/C catalysts, which demonstrates a significant impetus for stimulating the catalytic activity in fuel cells.