Affiliation:
1. Key Laboratory of Catalytic Conversion and Clean Energy in Universities of Shandong Province, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, P. R. China
Abstract
The application of sulfonated poly (ether ether ketone) (SPEEK) membrane in vanadium redox flow batteries (VRFBs) is hindered by the trade-off between proton conductivity and ion selectivity. To optimize its performance, the metal-organic frameworks loaded with phytic acid (PA-UiO-66-NH2) are introduced into the SPEEK matrix to construct a proton-selective transport channel. Better proton conductivity and ion selectivity are achieved in composite membranes due to the unique porous structure and chemical characteristics of PA-UiO-66-NH2 fillers. When the PA-UiO-66-NH2 content is at 2 wt%, the S/PA-UiO-66-NH2-2 membrane exhibits higher proton conductivity (35.3 mS cm−1) and ion selectivity (41.0 × 103 S min cm−3) compared to other composite membranes, pristine SPEEK and commercial Nafion 212 membranes. As a result, the S/PA-UiO-66-NH2-2 membrane shows excellent energy efficiencies (88.1%-74.0%) at current densities ranging from 60 to 180 mA cm−2. The cell efficiencies maintain stability during the 300 times charge-discharge cycle, proving the outstanding stability and durability of the S/PA-UiO-66-NH2-2 membrane in a strong acidic and oxidizing environment. These results suggest that the combination of phytic acid and metal-organic framework can effectively improve the performance of the membranes, and it also can be further utilized to solve other challenges in the membrane separation field.
Funder
Natural Science Foundation of Shandong Province