Insights Into the Thermal Stability and Proton Transport Mechanism of <scp>PTFE</scp>‐Nafion Composite Membranes
Sixiu Zeng, Yuexi Zeng, Jiangping Song, Zihan Meng
Abstract
ABSTRACT The controllable design of proton exchange membranes (PEMs) with outstanding temperature resistance and efficient proton conduction is essential for high‐temperature PEM fuel cells. In this study, a polytetrafluoroethylene (PTFE)‐Nafion composite PEM was prepared using immersion and high‐temperature heat treatment methods. To understand the thermal stability, the glass transition temperatures of the PTFE‐Nafion and Nafion membranes were tested using static thermomechanical analysis. The PTFE‐Nafion membrane had a higher glass transition temperature than the Nafion membrane. In terms of the microstructure, the PTFE‐Nafion composite membrane exhibited a slightly larger ion domain structure than the Nafion membrane, and the first scattering peak of the PTFE‐Nafion composite membrane appeared at q ≈ 0.018 nm −1 , while the pure Nafion membrane peak was located at q ≈ 0.022 nm −1 . The PTFE‐Nafion composite membrane also exhibited higher proton conductivity than the Nafion membrane, and the activation energy of the Nafion membrane was approximately 3.5 times higher than that of the PTFE‐Nafion composite membrane. These results demonstrated the difference in proton transport mechanism for the PTFE‐Nafion composite and pure membranes, which may help guide the rational design of PEMs for fuel cells operating in high‐temperature and low‐humidity environments.