Highly ion-conductive anion exchange membranes with superior mechanical properties based on polymeric ionic liquid filled functionalized bacterial cellulose for alkaline fuel cells

How to simultaneously improve the ionic conductivity and mechanical properties is a key problem facing currently used anion-exchange membranes (AEMs). Here, biomass-based bacterial cellulose (BC) was used as a porous template to make TiO2 localized mineralization around the surface of BC nanofibers, and constructed a TiO2-coated BC porous substrate (TiO2@BC) with hierarchical structure. Then, the coated TiO2 nanoparticles was densely grafted by quaternary ammonium groups to obtain high ionic conduction ability. After filling with a polymeric ionic liquid (PIL) with high ion exchange capacity through in situ polymerization and crosslinking, the obtained novel PIL-filled AEM possessed ultrahigh ionic conductivity of 100.5 mS cm−1 at 80 °C, which was 72.1% higher than that of the PIL-filled pure BC membrane (only 58.4 mS cm−1). Moreover, by the aid of the synergistic reinforcement effect of TiO2@BC, the membrane exhibited extremely high dry strength of 95.3 MPa and satisfactory wet strength and flexibility. When at fully hydrate state, the membrane with the size of 1 × 4 cm (width × length) can hang a bottle containing 1000 g of water. The single cell equipped with this membrane output the peak power density of 40.2 mW cm−2, showing its great potential as a high-performance biomass-based AEM.