Electrochemical Interface Optimization toward Low Oxygen Transport Resistance in High‐Temperature Polymer Electrolyte Fuel Cells

Due to the enhanced tolerance of CO‐containing species under elevated operation temperature around 150–220 °C, high‐temperature polymer electrolyte fuel cells (HT‐PEFCs) have drawn extensive interest in the recent decades. One of the major challenges remaining for HT‐PEFCs is the inferior cell performance ascribed to poor catalytic activity and mass transport, which are mainly determined by the electrochemical interface structure involving phosphoric acid electrolyte. Herein, the electrochemical interfaces are investigated and optimized by adjusting the hydrophilic phases within the catalyst layer (CL) to modulate phosphoric acid redistribution in the cathode. The electrochemical surface area and interfacial oxygen transport resistance in the CL are optimized by balancing the coverage of polytetrafluoroethylene (PTFE) and phosphoric acid on the catalyst surface, thus achieving an enhanced cell performance of the HT‐PEFC of up to 328.12 mW cm −2 . This balancing strategy for optimizing the electrochemical interfacial structure could shed light on the development of electrode architecture design for energy conversion and storage devices.