In this study, with the motivation of elucidating the effect of H₂S and HCl on solid oxide fuel cell anodes, nickel and ceria pattern anodes are prepared on yttrium-stabilized zirconia electrolyte, and the effect of H₂S and HCl on their performance is tested using electrochemical impedance spectroscopy. However, it has been found that while H₂S adversely impacts both nickel and ceria, the poisoning caused is reversible for nickel and only partially reversible for ceria. Poisoning kinetics are similar and fast for both materials, while recovery kinetics are slower for ceria than nickel. High sulfur coverage is the rate-limiting factor inferred from the elementary kinetic modeling. Unlike H₂S, the presence of HCl appeared to be favorable for electrochemical oxidation as the polarization resistance of both pattern electrode cells decreased upon feeding HCl contaminated hydrogen gas. Similar behavior has not been reported previously, and the conclusion regarding underlying mechanisms requires further investigation.

Energy and exergy performance of ammonia fuelled solid oxide fuel cell (SOFC) integrated system in wastewater treatment plants (WWTPs) is evaluated in this study. Ammonia can be recovered through a struvite precipitation process in the form of an ammonia-water mixture (with 14 mol.% ammonia) and used as a carbon-free fuel. A series of experiments has been conducted for SOFC single cell to evaluate the performance with different ammonia-water mixture ratios. An ammonia-SOFC system was modeled in Cycle Tempo for detailed thermodynamic analysis. The heat from the electrochemical reaction in the SOFC and catalytic combustion in an afterburner is used in the struvite decomposition process. However, the generated heat is not sufficient to meet the heat demand of the struvite decomposition reactor. To improve the sustainability of the system in terms of heat demand, the system can be integrated into a heat pump assisted distillation tower, meanwhile, the ammonia concentration of the fuel stream increases. Increasing the ammonia concentration to 90 mol.% increases the energy and exergy efficiencies of the SOFC system. The net energy efficiency of the integrated system with a heat pump assisted distillation tower is 39%, based on the LHV of the ammonia-water mixture.

Fundamental studies focusing on the electrode kinetics are essential in understanding the fuel cell operation and optimizing the electrode designs. In this study, we determined the triple-phase boundary (TPB)-based kinetics of hydrogen electrochemical oxidation using nickel patterned electrode experimental data and the Butler-Volmer formalism of the oxidation process. The same kinetics are then incorporated in a cermet electrode electrochemical model to estimate the effective TPB density of the nickel/yittrium-stabilized zirconia cermet anode. The kinetics are found to be of the same order of magnitude as previously determined by the microstructure reconstruction of cermet anode. Simulation results further revealed that the effective TPB density is several orders of magnitude lower than the typically reported physical densities of the cermet anode that possibly suggests that only a minor fraction of the physical TPB is actually required or available to produce the cell current at given cell voltage. The effect of various operating conditions on the anode activation overpotential is also investigated and discussed in this study.

Bi-directional solid oxide cell systems (Bi-SOC) are being increasingly considered as an electrical energy storage method and consequently as a means to boost the penetration of renewable energy (RE) and to improve the grid flexibility by power-to-gas electrochemical conversion. A major advantage of these systems is that the same SOC stack operates as both energy storage device (SOEC) and energy producing device (SOFC), based on the energy demand and production. SOEC and SOFC systems are now well-optimised as individual systems; this work studies the effect of using the bi-directionality of the SOC at a system level. Since the system performance is highly dependent on the cell-stack operating conditions, this study improves the stack parameters for both operation modes. Moreover, the year-round cumulative exergy method (CE) is introduced in the solid oxide cell (SOC) context for estimating the system exergy efficiencies. This method is an attempt to obtain more insightful exergy assessments since it takes into account the operational hours of the SOC system in both modes. The CE method therefore helps to predict more accurately the most efficient configuration and operating parameters based on the power production and consumption curves in a year. Variation of operating conditions, configurations and SOC parameters show a variation of Bi-SOC system year-round cumulative exergy efficiency from 33% to 73%. The obtained thermodynamic performance shows that the Bi-SOC when feasible can prove to be a highly efficient flexible power plant, as well as an energy storage system.

Using the Nernst-Planck-Poisson model and a detailed reaction mechanism, we studied the hydrogen electrochemical oxidation on a ceria anode. Resistances caused by surface kinetics, and bulk transport of oxide-ion vacancies and electrons are computed individually to identify the dominant resistive process. The effect of operating conditions like temperature and gas-phase composition on the polarization resistance is evaluated and compared with the experimental data obtained by Electrochemical Impedance Spectroscopy (EIS). The rate-determining step is found to be the charge-transfer reaction in which hydrogen adsorbs at the surface oxide ions and forms hydroxyls along with the charge-transfer to adjacent cerium ions. Based on the rate-determining step, the exchange-current density is also calculated and validated with the experimental data.

Fuel flexibility of solid oxide fuel cells enables the use of low cost and practical fuels like syngas. Understanding of the oxidation kinetics with syngas is essential for proper selection of anode material and its design optimization. Using nickel and ceria pattern anodes, we study the electrochemical oxidation of syngas in both dry and wet environments. In dry environment, the polarization resistance of CO oxidation drops drastically with the addition of small amounts of hydrogen to CO gas stream. In wet environment (4 % moisture), the polarization resistance of CO is only slightly higher than syngas and hydrogen. Observation in the first case is related to the hydrogen preferential oxidation whereas latter is a combined effect of water gas shift reaction and preferential oxidation of hydrogen. Kinetic modeling is also carried out to understand hydrogen and CO co-oxidation. Simulation suggests that CO, besides hydrogen, may also electrochemically oxidize depending upon its concentration in the syngas. At higher concentration, CO electrochemical oxidation may be non-negligible especially in case of ceria anodes.