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In this paper, we experimentally studied an air breathing high temperature PEM fuel cell at steady operating conditions to investigate the effects of CO poisoning at different temperatures ranges between 120°C∼180°C. The effects of changes in temperatures with different amount of CO poisoning on the current-voltage characteristics of the fuel cell are investigated. Experimental data of this type would be very useful to develop design parameters of fuel processor based on reformate hydrocarbons. The high CO tolerance of high temperature PEM fuel cells makes it possible to use the reformate gas directly from the reformer without further CO removal. Here we considered the fact that a steam reformer is a consumer of heat and water, and fuel cell stacks are a producer of heat and water. Thus, integration of the fuel cell stack and the reformer is expected to improve the system performance. The results obtained from the experiments showed variations in current-voltage characteristics at different temperatures with different CO poisoning rates. The results will help to understand the overall system performance development strategy of high temperature PEM fuel cell in terms of current-voltage characteristics, when fed with on-site reformate hydrogen gas with variable CO concentrations.

The high temperature proton exchange membranes (HT-PEM) attract growing interests due to its enhanced electrochemical kinetics, simplified pinch technology and utilization of higher CO-rich reformed hydrogen as the fuel. From the technological point of view, using pure hydrogen as fuel seems highly restrictive because hydrogen with high purity may not always be readily available. As an attractive alternative to compressed hydrogen, it is preferred to use hydrogen-rich gases as fuel. On-site generation of hydrogen using reformed fuels can be directly fed to the high temperature proton exchange membrane fuel cells (HT-PEMFCs) without first preheating the cell with external heat source to raise the temperature to its operating temperature. Since the HT-PEMFCs performance depends strongly on temperature, the cell temperature plays an important role in its operation. The purpose of this research is to experimentally study a high temperature PEM fuel cell at steady operating conditions. In this work, the performance of the fuel cell has been experimentally examined to unravel the steady-state effects of changes in temperature and pressure at a fixed hydrogen stoichiometry and variable air stiochiometries In particular, the effects that changes in temperature and pressure have on the voltage-current characteristics. Experimental data of this type is needed to develop and validate the fuel cell models, and to help understand and optimize the operation of these devices. In this study, a cell with an active cell area of 45 cm2 based on polybenzimidazole (PBI), doped with phosphoric acid is examined over the entire temperature range of 120°C–180°C with hydrogen of 99.999% purity. The quantitative results obtained from the experiments showed variations in current-voltage characteristics at different pressure and temperatures. The results will be used as a baseline value to under-study the performance of a high temperature PEM fuel cell in terms of current-voltage characteristics, when fueled with a reformate with higher CO concentrations in our future study.

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A robust control strategy which ensures optimum performance is crucial to proton exchange membrane (PEM) fuel cell development. In a PEM fuel cell stack, the primary control variables are the reactant’s stochiometric ratio, membrane’s relative humidity and operating pressure of the anode and cathode. In this study, a 5 kW (25-cell) PEM fuel cell stack is experimentally evaluated under various operating conditions. Using the extensive experimental data of voltage-current characteristics, a feed forward control strategy based on a 3D surface map of cathode pressure, current density and membrane humidity at different operating voltages is developed. The effectiveness of the feed forward control strategy is tested on the Green-light testing facility. To reduce the dependence on predetermined system parameters, real-time optimization based on extremum seeking algorithm is proposed to control the air flow rate into the cathode of the PEM fuel cell stack. The quantitative results obtained from the experiments show good potential towards achieving effective control of PEM fuel cell stack.

A hyper-branched polymer (HBP) electrolyte is synthesized for rechargeable lithium-air (Li-air) battery cell and experimentally evaluated its performance in actual battery cell environment. Several real-world battery cells were fabricated with synthesized HBP electrolyte, pure lithium metal as anode and an oxygen permeable air cathode to evaluate reproducibility of the rechargeable Li-air battery cell. The effect of various conditions such as various HBP based electrolytes, discharge current −0.1∼0.5 mA, cathode preparation processes and carbon contents on the battery cell performance were experimentally evaluated using the fabricated battery cells under dry air condition. Detailed HBP electrolyte synthesis procedures and experimental performance evaluation of Li-air battery cell for various conditions are presented. The experimental results showed that different conditions and processes significantly affect the Li-air battery performance. Upon taking into account the effect of different conditions and processes, optimized HBP electrolyte materials, cathode process and conditions were determined. Several Li-air battery cells were fabricated with optimized conditions and optimized battery cell materials to determine the reproducibility and performance consistency. Experimental results showed that over 55-65 h of discharge occurred over 2.5 V terminal cell voltage with all three optimized Li-air battery cells. It implied that the optimized Li-air battery cells were reproducible and were able to hold charge over 2.5 V for more than 2 days. Experimental results of the Li-air battery cell with further refined optimized materials revealed that the battery cell can discharge more than 10 days (i.e., more than 250 h) at or above 2.0 V. The experimental results also showed that the Li-air battery discharge time got shorter as the discharge-charge cycle increases due to increase in internal resistances of battery cell materials. The experimental results confirmed that the lithium-air battery cell can be reproduced without loss of performance and can hold charge more than 10 days at or over 2.0 V. The investigation results obtained may usher a pathway to manufacture a long-life rechargeable Li-air battery cell in the near future.

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