Poly(biphenyl-piperidinium)/poly(biphenyl-trifluoroacetophenone) random and block copolymers enabling highly stable anion exchange membranes for water electrolysis

Anion Exchange Membrane Water Electrolyzers (AEM-WE) are a promising technology for green hydrogen production. Their development into commercial devices is however hindered by the low AEM durability in alkaline environment. Poly (aryl piperidinium)s (PAPs) AEMs are perhaps the most stable class of AEMs due to the combination of heteroatom-free aromatic backbone and piperidinium cation. Previous works showed the benefits arising from copolymerization of n-methyl-piperidone with trifluoroacetophenone; lower swelling ratio and better mechanical properties are achieved maintaining hydroxide conductivity above 100 mS cm−1. Despite these results, limited attention has been devoted to this chemistry. In this work we propose a further engineering step through a block copolymerization of the two monomers. A full characterization of AEMs is provided. Block copolymers achieved high conductivity of 130 mS cm−1 with a very small swelling ratio (7 % @ 80 °C). We report a complete WE cell test of these copolymers. Block copolymers-based AEMs reach a current density of 2.5 A cm−2 (2.2 V, 60 °C). Random copolymers-based AEMs are more durable, showing no current density decrease in a cell test of 1500 h (1.8 V, 60 °C).