Fig. 18.a. polarization curves for the alkaline water electrolysis with NPBI-BS-47 ISM at different concentrations of KOH; b. Nyquist plots of EIS spectra (0.1 A∙cm−2) of NPBI-BS-47 membrane at different concentrations of KOH. Reproduced with permission of Ref. [65]. Copyright 2022, Elsevier.