Tailored physicochemical microenvironments in stacked graphene oxide nanochannels give membranes with fast and highly selective CO2 transport.

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Anion-exchange membrane fuel cells (AEMFCs) are a promising, next-generation fuel cell technology. AEMFCs require highly conductive and robust anionexchange membranes (AEMs), which are challenging to develop due to the tradeoff between conductivity and water uptake. Here we report a method to prepare high-molecularweight branched poly(aryl piperidinium) AEMs. We show that branching reduces water uptake, leading to improved dimensional stability. The optimized membrane, b-PTP-2.5, exhibits simultaneously high OH À conductivity (> 145 mS cm À 1 at 80 °C), high mechanical strength and dimensional stability, good processability, and excellent alkaline stability (> 1500 h) in 1 M KOH at 80 °C. AEMFCs based on b-PTP-2.5 reached peak power densities of 2.3 W cm À 2 in H 2 À O 2 and 1.3 W cm À 2 in H 2 -air at 80 °C. The AEMFCs can run stably under a constant current of 0.2 A cm À 2 over 500 h, during which the b-PTP-2.5 membrane remains stable.

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Anion-exchange-membrane fuel cells (AEMFCs) are a cost-effective alternative to proton-exchange-membrane fuel cells (PEMFCs). The development of high-performance and durable AEMFCs requires highly conductive and robust anion-exchange membranes (AEMs). However, AEMs generally exhibit a trade-off between conductivity and dimensional stability. Here, a fluorination strategy to create a phase-separated morphological structure in poly(aryl piperidinium) AEMs is reported. The highly hydrophobic perfluoroalkyl side chains augment phase separation to construct interconnected hydrophilic channels for anion transport. As a result, these fluorinated PAP (FPAP) AEMs simultaneously possess high conductivity (>150 mS cm −1 at 80 °C) and high dimensional stability (swelling ratio <20% at 80 °C), excellent mechanical properties (tensile strength >80 MPa and elongation at break >40%) and chemical stability (>2000 h in 3 m KOH at 80 °C). AEMFCs with a non-precious Co-Mn spinel cathode using the present FPAP AEMs achieve an outstanding peak power density of 1.31 W cm −2 . The AEMs remain stable over 500 h of fuel cell operation at a constant current density of 0.2 A cm −2 .

Facilitated transport membranes, with uniform distribution of the facilitated transport carriers, are highly desirable to reduce the separation energy barrier. Nevertheless, the disordered and random assembly of the membrane building...