Composite proton exchange membranes based on inorganic proton conductor boron phosphate functionalized multi-walled carbon nanotubes and chitosan

Super inorganic proton conductor boron phosphate (BPO 4 ) was utilized to functionalize the multi-walled carbon nanotubes (MWNTs) through a convenient sol-gel method with the assist of polydopamine (PDA) to yield BPO 4 coated MWNTs (BPO 4 @MWNTs). Then the BPO 4 @MWNTs was dispersed in dilute chitosan (CTS) solution to fabricate CTS/BPO 4 @MWNTs composite membrane . The CTS/BPO 4 @MWNTs composite membranes showed superior performances in thermal stability, mechanical property and oxidation stability due to the well-dispersed BPO 4 @MWNTs in CTS matrix and the optimized interface compatibility between the BPO 4 @MWNTs and the CTS matrix. Moreover, BPO 4 coated on the surface of MWNTs can provide an extra proton conducting pathway render the CTS/BPO 4 @MWNTs-2 composite membrane showed the proton conductivity of 0.040 S cm −1 at 80 °C and the maximum power density of 49.0 mW cm −2 at 70 °C and 2 M methanol concentration much higher than that for original CTS membranes.