Highly ion-selective sulfonated poly (4,4′-diphenylether-5,5′-bibenzimidazole) membranes for vanadium redox flow battery

Figures & data

Figure 1. FT-IR spectra (a) and ¹H NMR spectra(b) of SOPBI membranes.

Scheme 1. Synthesis procedures of OPBI and SOPBI.

Figure 2. Surface (a) and cross-section (b) morphology SOPBI membranes.

Figure 3. TEM images of SOPBI membranes.

Figure 4. Thickness, H₂SO₄ doping level, SR, IEC and area resistance of the SOPBI membranes.

Figure 5. Tensile stress versus elongation of 3 M H₂SO₄ doped SOPBI membranes.

Figure 6. (a–d) Photos of diffusion cell at RT for 168h; (e)The concentration of the VO²⁺ ions in the receiving reservoir of the diffusion cell with membranes as a function of time.

Figure 7. (a) The molecular structure and (b) the electrostatic potential of SOPBI, (c) The molecular structures and (d) the binding energy of SOPBI-H1 and SOPBI-H2.

Figure 8. (a) Schematic illustration of an all-vanadium redox flow batteries; (b) Charge-discharge curves of various membranes at a current density of 100 mA cm⁻²; CE (c), VE (d) and EE (e) of VRFB single cells assembled with: Nafion212 and SOPBI membranes at various current densities; (f) Cycling performance of the VRFB single cell with SOPBI at 120 mA cm⁻².

Data availability statement (DAS)

The authors confirm that the data supporting the findings of this study are available within the article.