Polymeric Anion Exchange Membranes for Green Hydrogen Production

Abstract

Producing green hydrogen by using anion exchange membrane (AEM) water electrolysis is a promising approach to address the severe climate and energy crisis facing human society and aid the transition to net-zero emissions. AEM electrolysis can be integrated with renewable energy sources and utilizes cost-effective (Pt-free) electrocatalysts and other inexpensive components in stacks. To enable commercially viable hydrogen generation, improvement of the AEM component is imperative, and the goal of fabricating a membrane, in which the chemical, mechanical and electrochemical requirements are combined and optimized in a synergistic way, still represents a challenging task.The present work was, therefore, aimed at addressing several unique features of AEMs for implementation in an industrially scalable and sustainable energy-production process through a suitable synthetic strategy that involves the post-modification of a commercially available and relatively cheap poly(styrene-b-butadiene) (SB)-based block copolymer matrix by grafting vinylbenzyl chloride (VBC). The synthesized SB-g-VBC copolymers were, therefore, used for the fabrication of AEMs by solution casting followed by quaternization reaction with trimethylamine (TMA) for the quantitative conversion of –CH2Cl into –CH2(CH3)3N+ groups. Obtained AEMs were thermally, mechanically and electrochemically characterized. By varying the VBC functionalization degree of the copolymers it was possible to modulate the ionic exchange capacity, conductivity, water uptake and mechanical properties of the membranes derived therefrom. The most promising AEMs were selected for testing in electrolytic cells (Figure 1) and were found to resist to real operating conditions for more than 40 days. Acknowledgements. The authors thank the company Enapter s.r.l. for the contribution to the electrochemical characterization and the financial support.Figure.1 Polarization curves of the SB-g-VBC based AEM as a function of residence time in an electrolytic cell (KOH 1 wt % at 55 °C). Figure 1