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Summer 2012 Blog - Yuanxi Chao

Yuanxi Chao is spending nine weeks at Academia Sinica in Taiwan.

July 4, 2012


Fuel Cell Educational Demonstrator (FCED) for testing the performance of hydrogen fuel cells

Last week, Dr. Du had planned on making a Polybenzimidazole (PBI) membrane herself rather than using the commercial PBI membranes. PBI membrane is a proton-exchange membrane that works in a relatively high temperature. Making the PBI membranes ourselves would allow us to control the proton conductivity and the mechanical strength of the membrane by modifying the synthesis procedure, so that we would be able to study the influence of the proton conductivity/mechanical strength of the membrane on cell performance. Unfortunately, we still do not have all the necessary chemicals for the PBI-membrane synthesis yet. So Dr. Du decided to run a test on the impedance of the commercial PBI membranes instead. We tried to derive an equivalent circuit for the testing membrane and use it to calculate the calculated impedance. We also found some articles online that analyzed the theoretical impedance of PBI membrane for comparison. In the end of the second week, I finally got a chance to get my hands on PECVD to grow carbon nanotubes (CNTs) on carbon clothes. We use the carbon cloth with CNTs on it as the cathode in our fuel cell.

We received all the chemicals that we needed for synthesizing PBI membrane in the third week of my internship. After we mixed all the reactants together (in a three-neck flask inside a heating mantle), we put the whole setting on a magnetic stirrer. But it turns out that magnetic stirrer is not powerful enough to stir our reactants! The viscous polyphosphoric acid has to be stirred by a mechanical stirrer, which we unfortunately do not have. We visited a lab in National Taiwan University of Science and Technology (NTUST) because they have a powerful mechanical stirrer there. The NTUST kindly agreed to help us produce PBI membranes. However, we have to accommodate their schedule, and the whole procedure of producing a PBI membrane takes almost a week. So will probably only have time to construct one or two batches of cells to test before leaving Taiwan.

Last week, which was the fourth week since I got Taiwan, we went to the lab in NTUST frequently to discuss with them about the PBI membrane synthesis procedure. We read dozens of papers that discussed the properties of different types of PBI, and the synthesis procedures there. Finally, we decided to synthesize para-PBI membrane. Dr. Du had already run the performance tests a couple weeks ago on the hydrogen fuel cells with commercial PBI membranes which had a thickness around 40 micrometers. The performance of those cells however were unsatisfactory; we believe that the relative high electron conductivity of the thin membrane was reducing the cells performance. We hope to get better results with thicker membranes, which should have a higher electron resistance. The PBI membrane synthesis began last Wednesday.
June 20, 2012

I arrived in Taiwan two weeks ago. My research at Academia Sinica concerns hydrogen fuel cells in Dr. Kuei-Hsien Chen’s laboratory. A researcher in the Institute of Atomic and Molecular Sciences (IAMS), Dr. Chen has a professor at National Taiwan University (NTU). His Advanced Materials Laboratory at the Center of Condense Matter Science (CCMS) is located on NTU campus. Another professor from NTU, Dr. Li-Chyong Chen, manages the lab. Both professors are always extremely busy; therefore, I’m actually working with a postdoc, Dr. Heyun Du, on her Proton Exchange Membrane Fuel Cell (PEMFC) project.

My summer project focuses on optimizing cell performance through a clean energy source, hydrogen. Releasing energy but produces only water when it reacts with oxygen, hydrogen oxidizes at the anode in a hydrogen fuel cell. Oxygen is then reduced at the cathode. During an oxidation/reduction reaction, the charge transfer must occur between the cathode and the anode. The electron transfer through output cable generates a current. The proton transfers through a membrane which only conducts the proton. No electron or any gas passes through the membrane. My summer research focuses on optimizing the cell performance, thus facilitating clean energy.

I spent most of the first week in the lab learning the equipment and watching the postdocs’ and scientists’ experiments. Additionally, some time was spent reading about procedures concerning construction of a hydrogen fuel cell and the function of each cell component. Since I’ve never worked in any chemistry lab before, almost all of the equipment in the lab was new to me.

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