Sodium

Quantum mechanics

Power density

Catalysis

Engineering

Mesoporous material

Nafion

Electrochemistry

Metallurgy

Materials science

Cathode

Covalent organic framework

Power (physics)

Chemical engineering

Ionomer

Porosity

Physical chemistry

Polymer

Physics

Organic chemistry

Copolymer

Sulfonate

Composite material

Ionic bonding

Chemistry

Electrode

Covalent bond

Science

Lowering platinum (Pt) loadings without sacrificing power density and durability in fuel cells is highly desired yet challenging because of the high mass transport resistance near the catalyst surfaces. We tailored the three-phase microenvironment by optimizing the ionomer by incorporating ionic covalent organic framework (COF) nanosheets into Nafion. The mesoporous apertures of 2.8 to 4.1 nanometers and appendant sulfonate groups enabled the proton transfer and promoted oxygen permeation. The mass activity of Pt and the peak power density of the fuel cell with Pt/Vulcan (0.07 mg of Pt per square centimeter in the cathode) both reached 1.6 times those values without the COF. This strategy was applied to catalyst layers with various Pt loadings and different commercial catalysts.

Covalent organic framework–based porous ionomers for high-performance fuel cells