Sustainion Imidazolium‐Functionalized Polymers for Carbon Dioxide Electrolysis

• Published in: Energy technology (Weinheim, Germany) Germany), 2017-06, Vol.5 (6), p.929-936
• Main Authors: Kutz, Robert B., Chen, Qingmei, Yang, Hongzhou, Sajjad, Syed D., Liu, Zengcai, Masel, I. Richard
• Format: Article
• Language: English
• Subjects: anion exchange membrane; Carbon dioxide; Carbon monoxide; Climate change; Conversion; Electrolysis; Electrolytic cells; energy storage; Fuels; Ionic liquids; Membranes; nitrogen heterocycles; Polymers; Selectivity; Styrene
• ISSN: 2194-4288; 2194-4296
• DOI: 10.1002/ente.201600636

CO2 electrolysis is a key step in CO2 conversion into fuels and chemicals as a way of mitigating climate change. We report the synthesis and testing of a series of new anion‐conductive membranes (tradenamed Sustainion™) for use in CO2 electrolysis. These membranes incorporate the functional character of imidazolium‐based ionic liquids as co‐catalysts in CO2 reduction into a solid membrane with a styrene backbone. We find that the addition of an imidazolium group onto the styrene side‐chains increases the selectivity of the reaction from approximately 25 % to approximately 95 %. The current at 3 V is increased by a factor of 14. So far we have been able to tune these parameters to achieve stable cells that provide current densities higher than 100 mA cm−2 at 3 V cell potential with a CO product selectivity over 98 %. Stable performance was observed for 6 months of continuous operation (>150 000 000 turnovers). These results demonstrate that imidazolium polymers are ideal membranes for CO2 electrolysis. Membrane power: A new anion‐exchange polymer called Sustainion is described that acts as a co‐catalyst for CO2 reduction. The performance of the polymer is tested under a variety of conditions and compared to the performance of commercially available polymers. We achieve far higher rates and selectivities. Further enhancements are also explored.