Development of highly alkaline stable anion conductive polymers with fluorene backbone for water electrolysis

Anion exchange membrane water electrolysis (AEMWE) is currently paying attention as a new hydrogen (H-2) production method since it can operate at high current densities using inexpensive nonnoble metal catalysts. However, the significant problems of AEMs, including their insufficient anion conductivity and alkaline stability, prevent the practical usage of AEMWE. We show a novel anion conductive polymer, alkyl trimethylammonium-substituted polyfluorene (TMA-PF), bearing no heteroatom bonds in the main chain. The TMA-PF membrane possesses higher anion conductivity than conventional AEMs due to the increased flexibility and mobility of the alkylammonium side chains of TMA-PF. The TMA-PF membrane shows high-alkaline stability and maintains the initial ion conductivity after immersion in an aqueous NaOH solution (8 mol L-1) at 80 degrees C for 48 h. In the water electrolysis evaluation, the cell using the TMA-PF membrane exhibits a higher current density (400 mA cm(-2) at 2.03 V) than the cell using the conventional AEM at the same potential, indicating that the novel AEM has a high potential to generate H-2 effectively. Green hydrogen produced by AEMWE using renewable energy will be an environmentally benign energy source without CO2 emissions.