19b.Novel Reinforced Anion Exchange Membranes for Solar-to-Hydrogen Generators

The assembly of photoelectrochemical solar-to-hydrogen generators is currently limited by the availability of several key components, including ion exchange membranes that exhibit the transport and stability properties required for this application. Anion exchange membranes with high hydroxyl ion conductivity and extremely low permeability for hydrogen and oxygen gases, and high mechanical strength and chemical stability are sought by DOE for solar-to- hydrogen generator applications. This Small Business Innovation Research project aims to develop a novel high-performance anion exchange membrane for solar-to-hydrogen generator applications based on the current state-of-the-art anion conducting ionomers having the highest hydroxyl ion conductivity with a novel reinforcement approach by integration of an intriguing reinforcement support. In Phase I, the new reinforced membranes have been prepared and evaluated in terms of microstructural features, chemical stability, mechanical durability, and electrochemical properties, and tested for solar-to-hydrogen operation using a tandem PEC cell. The reinforced membrane attains high stability with significantly enhanced mechanical durability and has shown increased crossover resistance to hydrogen and oxygen gas permeation. Besides, the reinforced membrane shows increased hydroxyl ion conductivity relative to the non-reinforced membrane, which is an attractive feature unique to this novel membrane. Overall, this membrane has been demonstrated to have high potential of meeting DOE performance requirements for solar-to-hydrogen generator applications. The Phase II work is to build on the Phase I outcome and systematically optimize the material system, processing, and performance of the new membrane. The membrane will be comprehensively evaluated in terms of all relevant properties. Commercially viable prototype membranes will be produced and tested for full cell operation. Development of production scale-up scheme will also be initiated during Phase II. The expected product of the present effort is a new reinforced anion exchange membrane that critically determines performance of photoelectrochemical cells for solar fuels generators. Ion exchange membrane is also the key component in many other energy generation, conversion or storage systems, including fuel cells, electrolyzers, and redox flow batteries. The demand for ion exchange membranes used in such energy systems is very high and keeps increasing in the future.