Poly(vinyl benzyl methylpyrrolidinium) hydroxide derived anion exchange membranes for water electrolysis

Developing anion exchange membranes (AEMs) with a long lifespan is a considerable challenge for the electrolyte material in the alkaline water electrolysis. Herein, the methylpyrrolidinium cation functionalized poly(vinyl benzyl chloride) (PVBC-MPy) membrane with high alkaline stability and ion conductivity simultaneously was synthesized through a facile, gentle and non-carcinogenic chemical method. A poly(ether ketone-cardo) (PEK-cardo) polymer was blended with PVBC-MPy to provide sufficient mechanical robustness for integration and testing in AEM water electrolysis. The PVBC-MPy/x%PEK-cardo membranes showed excellent alkaline stability with no obvious degradation after immersing in 1 mol L⁻¹ KOH at 60 °C and 80 °C for more than 500 h. The PVBC-MPy/35%PEK-cardo membrane exhibited a good balance between high ion conductivity and mechanical strength, and was down-selected for electrolysis testing in 1 M KOH at 60 °C. The cell polarization curves of the AEM water electrolysis indicated that the membrane displayed good cell performance with a current density of 500 mA cm⁻² at 2 V at 60 °C. Moreover electrochemical impedance spectroscopy and the cell voltage lifetime test illustrated the feasibility of the membrane operating under mildly alkaline conditions.