Poly(triphenylene-piperidine) membranes reinforced by carboxy intrinsic microporous polymers towards high output power at low phosphoric acid levels for HT-PEMFC

To address the inferior mechanical properties associated with high phosphoric acid (PA) content, a rigid microporous polymer containing carboxyl groups (cPIM) was incorporated into poly (triphenylene-piperidine) (PTP) matrix to prepare composite membranes (PTP-xcPIM) for high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Compared to the original membrane (PTP/PA), the PTP-xcPIM/PA reinforced mem-branes exhibited improved mechanical properties (13-17 MPa) and higher proton conductivity (>90 mS cm(-1)@180(degrees)C) at a similar PA content. After assembling into a single HT-PEMFC, the reinforced composite membrane could achieve a high output power of over 1000 mW cm(-2). The addition of the microporous layer to the composite membranes significantly increased the PA retention due to its siphoning effect on PA. Especially, PTP-10cPIM/PA retained 57.64% of PA after 100 h at 60(degrees)C and 50%RH, while PTP/PA retained only 52.11% in the same harsh environment. These phenomena imply that the strategy of introducing rigid microporous poly-mers containing functional groups can lead to the simultaneous enhancement on the PA retention capacity and proton conductivity at low PA doping levels, and effectively avoid the "trade-off" effect between the mechanical properties and the output performance.