Investigation of NOx Generation and Ammonia Fuel Utilization in a Solid Oxide Fuel Cell

Abstract Decreasing the generation of CO2 from energy production is a key area in energy research and environmental sustainability. Fuel cells represent a solution to reducing CO2 generation through the use of hydrogen fuel to generate electricity. However, the widespread use of hydrogen fueled fuel cells is generally limited by difficulty of hydrogen storage, transportation, and synthesis. The primary issue with hydrogen storage is that gaseous hydrogen contains low volumetric energy density. One promising option to address these difficulties is the use of ammonia (NH3) in solid oxide fuel cells (SOFCs), which allows for storage of a liquid fuel source, rather than the highly compressed gaseous fuel. Previous work has shown that a SOFC using ammonia fuel is highly capable of generating electricity at levels comparable to that of pure hydrogen fuel. The nickel within the SOFC, along with the high operating temperatures, assists in the thermal cracking of ammonia. However, one missing piece from our previous work is an investigation of ammonia utilization. As such, this work will seek to evaluate the utilization though an exhaust gas analysis using mass spectroscopy and gas chromatography. Additionally, the exhaust gas composition is monitored for the presence of NOx group gases. With the use of ammonia as the fuel source, there is a possibility that we see nitrogen bonding to oxygen ions at the triple-phase boundary (TPB), leading to NOx formation. Given the danger presented by these gases, we must be certain that the concentrations are negligible, or that there will be sufficient NOx reduction strategies in the exhaust stream. SOFC performance results will be briefly discussed, along with an analysis of exhaust composition using gas chromatography and mass spectroscopy to demonstrate utilization of ammonia and evaluate NOx generation relative to fuel cell electrical performance at various operating temperature.