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

Super inorganic proton conductor boron phosphate (BPO4) was utilized to functionalize the multi-walled carbon nanotubes (MWNTs) through a convenient sol-gel method with the assist of polydopamine (PDA) to yield BPO4 coated MWNTs (BPO4@MWNTs). Then the BPO4@MWNTs was dispersed in dilute chitosan (CTS) solution to fabricate CTS/BPO4@MWNTs composite membrane. The CTS/BPO4@MWNTs composite membranes showed superior performances in thermal stability, mechanical property and oxidation stability due to the well-dispersed BPO4@MWNTs in CTS matrix and the optimized interface compatibility between the BPO4@MWNTs and the CTS matrix. Moreover, BPO4 coated on the surface of MWNTs can provide an extra proton conducting pathway render the CTS/BPO4@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.