Confinement–Induced N2–Phobicity Enables O2 Extraction from Air for Catalysis

Abstract 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.