Sy. Lee

Gradient Catalyst Coating for a Proton Exchange Membrane Fuel Cell Operation under Nonhumidified Conditions

Operation under nonhumidified conditions was demonstrated with a membrane electrode assembly (MEA) for a proton exchange membrane fuel cell. The Pt catalyst was coated with a gradient on the active area of a MEA; the catalyst amount was reduced gradually from cathode inlet to outlet. The MEA with the gradient coating method produced more water near the inlet site than that with the uniform coating method. The water was used to mitigate dryness of the MEA. The cell performance was improved by 17% at 800 mA/cm 2 under nonhumidified conditions by effective water management of the gradient coating method.

Complex Capacitance Analysis of Ionic Resistance and Interfacial Capacitance within Cathode Layers of PEMFC and DMFC Electrodes

In PEMFCs (polymer electrolyte membrane fuel cells) and DMFCs (direct methanol fuel cells), the catalyst layers are prepared together with a Nafion ionomer to extend reaction sites throughout the bulk electrodes. In order to achieve high performances with the large TPB (three-phase boundary) area, the catalyst layers should have well-developed networks for electron conduction (catalyst particles), proton transport (Nafion ionomer particles), and reactant gas supply (pores). Therefore, characterization of the microstructures of catalyst layers, as well as performance measurements, is very important to optimize various preparation factors. Also, the microstructure characterization is required to elucidate degradation mechanisms for practical fuel cell operation. In this study, a complex capacitance analysis of impedance data was developed to evaluate the catalyst/ionomer interfacial capacitance and ionic resistance of ionomer networks, without non-linear data fitting. Firstly, assuming no Faradaic reactions, equivalent circuits for the catalyst layers were suggested, which are similar to EDLC systems with porous carbon electrodes. Then, with the simulated complex capacitances, it was confirmed that the plots of the real and imaginary parts as a function of ac frequency are determined by the catalyst/ionomer interfacial capacitances and RC time constants, which are important characteristics for high fuel cell performances. Experimentally, the condition of no Faradaic reactions was realized by supplying nitrogen or water to the cathodes instead of air and fixing the dc potential at 0.4 V during the impedance measurements. By analyzing the real and imaginary capacitance plots of experimental impedance data, the catalyst/ionomer interfacial area and proton conductivity were graphically estimated. Also, the interfacial capacitances and ionomer resistances could be quantitatively determined from the real capacitance at low frequency and peak frequency in the imaginary capacitance plots. Here, the experimental impedance and transformed complex capacitances could be well described by equivalent circuits that contain the transmission line model. From the complex capacitance analysis of impedance data measured at 0.4 V under a N2/H2 atmosphere for PEMFC MEAs, it was found that the ionic resistance within cathode layers was higher for the MEA with lower ionomer content (20 wt.%), especially at low relative humidity. In single cell testing, the MEA with 20 wt.% ionomer showed larger activation overpotential, probably due to the limited utilization of active sites with high ionic resistances. 0 1 2 3 0 1 2

Abstract OT3-1-08: The PROCEED trial KCSG BR11-01: Phase III multicenter randomized open label study of irinotecan plus capecitabine versus capecitabine in patients previously treated with anthracycline and taxane for HER2 negative metastatic breast cancer

Background: Most patients with metastatic breast cancer (MBC) experience disease progression after being treated with an anthracycline or taxane. Irinotecan, a semisynthetic agent derived from the natural alkaloid camptothecin is metabolized to the active metabolite SN-38 which targets topoisomerase I leading to single and double strand DNA breaks. Irinotecan as a single agent demonstrated tumor activity with an objective response rate ranging from 5 to 23% in patients with MBC refractory to taxane and anthracycline. Irinotecan increased the activity of 5-FU, the active metabolite of capecitabine, and overcomes the negative effect of thymidylate synthase overexpression, which is the main target of an active metabolite of 5-FU. A phase II study that evaluated the efficacy and safety of irinotecan and capecitabin combination (IX) showed that the median progression free survival (PFS) was 7.6 months (95% CI, 5.0-10.2months), and the median OS was 22.6 months (95% CI, 15.4 – 29.8 months) with good tolerability in anthracycline and taxane pretreated MBC patients. Based on these results, we planned to conduct a multicenter, randomized phase III study which assesses the efficacy of irinotecan and capecitabine combination therapy compared with capecitabine alone in patients with anthracycline and taxane resistant MBC. Methods: In this trial, patients with HER2 normal tumor who previously received anthracycline and taxane based chemotherapies are enrolled. Eligible patients are randomly assigned in a 1:1 ratio to receive irinotecan plus capecitabine or capecitabine alone. The primary end point of this trial is PFS and a total number of accrual patients will be 222. Randomization is done using a random block size permutation method and stratified by hormone receptor status (negative vs. positive), first line vs. ≥second lines, visceral metastasis (negative vs. positive). Patients receive irinotecan at 80 mg/m2 on day 1 and 8 every 3 weeks and capecitabine 1000mg/m2 bid from day 1 to day 14 every 3 weeks. In control arm, patients receive capecitabine 1250mg/m2 bid from day 1 to day 14 every 3 weeks. Response will be assessed using RECIST1.1 criteria and toxicity will be graded according to NCI-CTCAE 4.0 criteria. Study Status: A total of 107 patients consented for the study since June 2011, and accrual is ongoing. Clinical trial information: NCT01501669. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-1-08.

Novel Membrane Electrode Assembly (MEA) Fabrication for PEMFC Operations under Non-humidified Conditions

The operation under non-humidified condition was demonstrated with novel MEA (membrane electrode assembly) for a PEMFC (proton exchange membrane fuel cell). For a conventional PEMFC operation, Pt is loaded uniformly on the whole active area of MEA. In the report, Pt catalyst was coated with a gradient on the active area of MEA. The catalyst amount was reduced gradually from cathode inlet to outlet. When the cell was fully humidified, the performance of gradient catalyst coated MEA was lower than that of the uniform catalyst coated one. However, when the cell was operated under non-humidified condition, the cell performance of the gradient catalyst coated MEA was higher than that of the uniform catalyst coated MEA. In the case of the gradient catalyst coated electrode, the amount of water which was generated at the cathode inlet site was relatively large compared to uniform catalyst coated one and the water was used to hydrate the MEA properly, resulting in higher cell performance under non-humidified condition.