Travis J Omasta

Preparation of radiation-grafted powders for use as anion exchange ionomers in alkaline polymer electrolyte fuel cells

A novel alkaline exchange ionomer (AEI) was prepared from the radiation-grafting of vinylbenzyl chloride (VBC) onto poly(ethylene-co-tetrafluoroethylene) [ETFE] powders with powder particle sizes of less than 100 μm diameter. Quaternisation of the VBC grafted ETFE powders with trimethylamine resulted in AEIs that were chemically the same as the ETFE-based radiation-grafted alkaline anion exchange membranes (AAEM) that had been previously developed for use in low temperature alkaline polymer electrolyte fuel cells (APEFC). The integration of the AEI powders into the catalyst layers (CL) of both electrodes resulted in a H2/O2 fuel cell peak power density of 240 mW cm−2 at 50 °C (compared to 180 mW cm−2 with a benchmark membrane electrode assembly containing identical components apart from the use of a previous generation AEI). This result is promising considering the wholly un-optimised nature of the AEI inclusion into the catalyst layers.

Beyond catalysis and membranes: visualizing and solving the challenge of electrode water accumulation and flooding in AEMFCs

A majority of anion exchange membrane fuel cells (AEMFCs) reported in the literature have been unable to achieve high current or power. A recently proposed theory is that the achievable current is largely limited by poorly balanced water during cell operation. In this work, we present convincing experimental results – coupling operando electrochemical measurements and neutron imaging – supporting this theory and allowing the amount and distribution of water, and its impact on AEMFC performance, to be quantified for the first time. We also create new electrode compositions by systematically manipulating the ionomer and carbon content in the anode catalyst layer, which allowed us to alleviate the mass transport behavior limitations of H2/O2 AEMFCs and achieve a new record-setting peak power density of 1.9 W cm−2 – a step-change to existing literature. Our efforts cast a new light on the design and optimization of AEMFCs – potentially changing the way that AEMFCs are constructed and operated.

Carbonate dynamics and opportunities with low temperature, AEM-based electrochemical CO2 separators

Fossil fuel power plants are responsible for a significant portion of anthropogenic atmospheric carbon dioxide (CO2) and due to concerns over global climate change, finding solutions that significantly reduce emissions at their source has become a vital concern. When oxygen (O2) is reduced along with CO2 at the cathode of an anion exchange membrane (AEM) electrochemical cell, carbonate and bicarbonate are formed which are transported through electrolyte by migration from the cathode to the anode where they are oxidized back to CO2 and O2. This behavior makes AEM-based devices scientifically interesting CO2 separation devices or “electrochemical CO2 pumps.” Electrochemical CO2 separation is a promising alternative to state-of-the-art solvent-based methods because the cells operate at low temperatures and scale with surface area, not volume, suggesting that industrial electrochemical systems could be more compact than amine sorption technologies. In this work, we investigate the impact of the CO2 separator cell potential on the CO2 flux, carbonate transport mechanism and process costs. The applied electrical current and CO2 flux showed a strong correlation that was both stable and reversible. The dominant anion transport pathway, carbonate vs. bicarbonate, undergoes a shift from carbonate to mixed carbonate/bicarbonate with increased potential. A preliminary techno-economic analysis shows that despite the limitations of present cells, there is a clear pathway to meet the US DOE 2025 and 2035 targets for power plant retrofit CO2 capture systems through materials and systems-level advances.

Water and Ion Transport in Anion Exchange Membrane Fuel Cells

Much of the work on Anion Exchange Membrane Fuel Cells (AEMFCs) in recent years has focused on the development of new catalysts and membranes. Though this work is important, it has overlooked mass transport in these systems, which is equally critical to achieving high performance. This chapter provides an overview of aspects related to AEMFC water management and carbonation upon exposure to carbon dioxide. managing both of these are needed in order to achieve high performing fuel cells.