There is a critical need to create more effective hydroxide exchange membranes to enable a new generation of alkaline fuel cells. Membranes must exhibit acceptable conductivity, alkaline stability, and easy fabrication to make the relatively inexpensive hydroxide exchange fuel cell (HEFC) a viable energy option. Although proton exchange fuel cells (PEFCs) have garnered much of the recent attention, the reaction of hydrogen to protons commonly requires expensive precious metal catalysts, such as platinum, which is both uneconomical and unsustainable for large-scale applications. By changing the operation of the fuel cell such that hydroxide is produced at the cathode and passed through the membrane, the PIs can employ cheaper catalysts, such as nickel alloy. The focus of this project is a synergistic collaboration between two PIs, having complementary skills in fuel cells and polymer networks. Together they plan to create a novel photo-cured, alkaline-stable, and inexpensive membrane material with high hydroxide conductivity. Specifically, the aims of the project are fourfold: 1) synthesize, crosslink, and characterize monomers and polymers having quaternary phosphonium pendant functional groups as well as photo-induced crosslinking capability using novel chemical schemes; 2) formulate these novel monomer and polymer compositions to optimize their membrane properties, such as swelling, mechanical strength, alkaline degradation resistance, and hydroxide conductivity for each of the three hydroxide exchange fuel-cell membrane layers: cathode, membrane, and anode; 3) create a membrane electrode assembly with the optimized materials, exploiting their spatiotemporal crosslinking control to fabricate complex HEFC designs as well as demonstrate the capability of these materials in device miniaturization and cell fabrication multiplexing; and 4) train a diverse group of undergraduate and graduate students in chemical synthesis, polymer chemistry, and membrane separations. Photo-mediated crosslinking will not only provide a dimensionally stable membrane, which is critical in HEFCs, but also enable a new method for fabricating complex membrane electrode assemblies. The results of this project will increase the understanding of how molecular composition influences membrane performance and properties. The proposed synthetic strategy allows the geometric configuration and membrane structure to be precisely tuned, which will provide insight into the complex interplay between hydroxide conductivity, gas exchange, and transport within a dimensionally stable membrane. Broader Impacts. Diverse personnel will be involved in a unique combination of chemical reactions and engineering, polymer engineering, and next-generation energy applications. The lead PIs are involved in outreach activities such as the University of Delaware Engineering Discovery Program, which targets K-12 students and parents. The PIs will develop a demonstration module to explain membranes to K-12 student and parents. The potential transformational aspect of the project is the fabrication of materials that will play a significant role in the realization of lower cost membranes for alkaline fuel cells, leading to an energy source with a low-carbon footprint.
