Precise Molecular‐Level Modification of Nafion with Bismuth Oxide Clusters for High‐performance Proton‐Exchange Membranes

Fabricating proton exchange membranes (PEMs) with high ionic conductivity and ideal mechanical robustness through regulation of the membrane microstructures achieved by molecular‐level hybridization remains essential but challenging for the further development of high‐performance PEM fuel cells. In this work, by precisely hybridizing nano‐scaled bismuth oxide clusters into Nafion, we have fabricated the high‐performance hybrid membrane, Nafion‐Bi12‐3 %, which showed a proton conductivity of 386 mS cm−1 at 80 °C in aqueous solution with low methanol permeability, and conserved the ideal mechanical and chemical stabilities as PEMs. Moreover, molecular dynamics (MD) simulation was employed to clarify the structural properties and the assembly mechanisms of the hybrid membrane on the molecular level. The maximum current density and power density of Nafion‐Bi12‐3 % for direct methanol fuel cells reached to 432.7 mA cm−2 and 110.2 mW cm−2, respectively. This work provides new insights into the design of versatile functional polymer electrolyte membranes through polyoxometalate hybridization. A hybrid membrane (Nafion‐Bi12‐3 %) used as a high‐performance proton exchange membrane (PEM) is fabricated through molecular‐level doping of {H6Bi12O16} clusters into ionic phase of Nafion. The clusters combine with anionic side chains of Nafion and optimize the hydrophilic/hydrophobic nano‐phases, resulting in hybrid membranes with high proton conductivity, ideal mechanical and chemical stability, and low methanol permeability.