No abstract

Incorporating acid proton carriers into a polymer matrix is an effective way to improve proton conductivity, but the immobilization of acids is a problem. In this work, mesoporous silica nanoparticles (MSNs) incorporating phosphotungstic acid (HPW) into sulfonated poly(ether ether ketone) (SPEEK) improved the conductivity of the proton exchange membrane. Meanwhile, the surface of the MSNs was aminated, and the ion interaction with SPEEK was established to increase the dispersion of MSNs. Composite membranes doped with surface-modified silica (K-MSNs) have excellent proton conductivity and conductivity stability. When the K-MSNs content was 1 wt%, the proton conductivity of the composite membrane reached 243 mS/cm at 60 C. After 240 hr of immersion at 60 C, proton conductivity was retained at 210 mS/cm. Compared with MSNs, K-MSNs has a large number of amino groups on its surface, which can effectively reduce the loss of HPW.

No abstract

In this work, we fabricated cross-linked pre-oxidized polyacrylonitrile nanofibers (PPNF) coating SO3H-UiO-66 coated (named SU6@PPNF), which was introduced into sulfonated poly (ether ether ketone) SPEEK to produce membrane with superior proton conductivity, dimensional stability and mechanical properties under hydrated condition. The membrane displays a maximum power density of 172.1 mW cm-2 under 100% RH and 60 °C, which is an increase of 12.2% compared with primary membrane.

Perfluorosulfonic acid (PFSA) polymer is considered as a proton exchange membrane material with great potential. Nevertheless, excessive water absorption caused by abundant sulfonic acid groups makes PFSA have low dimensional stabilities. In order to improve the dimensional stability of PFSA membranes, nanofibers are introduced into PFSA membranes. However, because nanofibers lack proton conducting groups, it usually reduces the proton conductivities of PFSA membranes. It is a challenge to improve dimensional stabilities while maintaining high proton conductivities. Due to the structural designability, covalent organic frameworks (COFs) with proton conductive groups are chosen to improve the overall performance of PFSA membranes. Herein, COFs synthesized in situ on three-dimensional PAN nanofibers were introduced into PFSA to prepare PFSA@PAN/TpPa-SO3H sandwiched membranes. The PFSA@PAN/TpPa-SO3H-5 composite membrane exhibited outstanding proton conductivity, which reached 260.81 mS·cm−1 at 80 °C and 100% RH, and only decreased by 4.7% in 264 h. The power density of a single fuel cell with PFSA@PAN/TpPa-SO3H-5 was as high as 392.7 mW·cm−2. Compared with the pristine PFSA membrane, the conductivity of PFSA@PAN/TpPa-SO3H-5 increased by 70.0 mS·cm−1, and the area swelling ratio decreased by 8.1%. Our work provides a novel strategy to prepare continuous proton transport channels to simultaneously improve conductivities and dimensional stabilities of proton exchange membranes.