Confinement-Induced N2-Phobicity Enables O2 Extraction from Air for Catalysis.

Air is commonly used as an oxidizer in proton-exchange membrane fuel cells. However, only 20.9% of air is oxygen and approximately 78% is nitrogen gas, which is inert and is often used to isolate oxygen. We report that N2-phobicity together with confinement-catalysis exponentially increases the power density of H2-air fuel cells by selectively transporting oxygen from the air into a confined space. N2-phobicity originates from a combination of low nitrogen diffusion within ordered 1D pores and the unusual confined nanospace with electron-rich Pt-N states that enhance the electrostatic repulsion force to nitrogen. The resulting fuel cell exhibited the highest mass activity, the lowest durability decline, and a record high current density of 707 mA cm-2 at 0.8 V.