An enhanced proton conductivity of proton exchange membranes by constructing proton-conducting nanopores using PVP-UiO-66-NH-SO3H nanoparticles

The performance of proton exchange membranes (PEMs) can be enhanced by creating continuous proton conduction channels. In this work, PVP-UiO-66-NH-SO3H nanoparticles (PUNSNPs) were prepared and filled into sulfonated poly (ether ether ketone) (SPEEK) to fabricate PUNSNPs/SPEEK composite PEMs. To further improve the performance of the PEMs, phosphoric acid (PA) was doped and a continuous nanopore network was formed in PA/PUNSNPs/SPEEK porous PEMs due to the dissolution of PUNSNPs. The PA/PUNSNPs/SPEEK porous PEMs have high PA uptake ratio (96%–117 %) and dimensional stability thanks to the anchoring effect of the nitrogen-containing heterocyclic ring on the PVP chains. The acid-base pairing interaction between the chains (residual ligands from PUNSNPs) inside the unique continuous nanopore structure allows PA/PUNSNPs/SPEEK = 20 % porous PEMs to have the highest proton conductivity of 0.350 S cm−1 (80 °C/100 % RH). Furthermore, the PA/PUNSNPs/SPEEK porous PEMs retained PA up to more than 80 % (80 °C, 40 % RH, 7 days). Similarly, PA/PUNSNPs/SPEEK = 20 % porous PEMs immersed in deionized water for 45 days were able to maintain a proton conductivity of more than 83 %. Finally, PA/PUNSNPs/SPEEK porous PEMs have low methanol permeability. Thus, this study provides a new method for the preparation of porous PEMs with a continuous nanopore network structure and excellent performance.