Polyhedral‐Oligomeric‐Silsesquioxane‐Based Binders Enable High‐Temperature Proton Exchange Membrane Fuel Cells with High Performance and Durability

ABSTRACT High‐temperature proton exchange membrane fuel cell (HT‐PEMFC) hold great potential for heavy‐duty vehicles, but one critical challenge for their practical application is high Pt catalyst loading, which primarily stems from Pt‐based catalyst poisoning and impaired proton transfer by phosphoric acid (PA) adsorption. In this work, polyhedral oligomeric silsesquioxane (POSS)‐based binders are successfully introduced into catalyst layers to reduce PA poisoning, improve proton transfer and hinder PA loss, as these binders have higher PA adsorption energy than Pt, enabling them to pull PA from Pt catalyst surface to reduce poisoning while bundled PA anion by POSS binder provides a fast proton transfer path for electrochemical reactions, thus significantly lowering high Pt loading. HT‐PEMFC with ─NH 2 group functionalized POSS binder in electrode achieve ultrahigh rated power density of 1.7 W cm −2 and Pt‐mass specific power density of 6.0 W mg pt −1 at 160°C @ 0.3 mg pt cm −2 . DFT calculations, in situ spectroscopy and 3D‐reconstruction are employed to clarify performance and durability enhancement mechanisms for promoting HT‐PEMFC’ commercial application.