Masato Ohashi

Aniline as a Cationic and Aromatic Contaminant in PEMFCs

Aniline as a possible contaminant in polymer electrolyte membrane fuel cells (PEMFCs) has been studied by several ex-situ techniques. The aniline isotherm for MEA shows more affinity to ion-exchange with the PEM than other monovalent such as sodium and ammonium ions, thus indicating stronger performance loss at the same concentration. The results of cyclic voltammetry (CV) of Pt/C show the loss of electrochemical surface area (ECSA) by with the addition of aniline in the electrolyte. The appearance of unknown peaks in CV may indicate the production of polyaniline (PANI) film which appears to grow with the number of CV tests. These studies indicate that the use of balance of plant components that leach aniline should be avoided since its presence appears to decrease the electrochemical activity of the electrode for the oxygen reduction reaction. Further studies on aniline with in-situ experiment may not be warranted.

Electrochemical Analysis of Microtubular SOFC under Fuel Contaminants

In the present study, the Solid Oxide Fuel Cells which are built by the National Metal and Materials Technology Center (MTEC) in Thailand were electrochemically characterized using polarization and transient techniques. The effect of diluting hydrogen with argon was studied and also the impact that the use of methane, as a zero order contaminant, was evaluated. To quantify the amount of carbon deposition, mass spectroscopy was used with samples collected at the outlet of the fuel cell during and after methane. The results obtained show that very small, and reversible, carbon deposition could be seen, as long as some current was applied to the fuel cell. However, if no current was applied while methane was flown, much stronger carbon deposition could be seen. This carbon deposition, at open circuit voltage proved to be irreversible leading to cell failure.

Understanding Differences in the Performance of Laboratory Scale PEMFCs: I. The Effect of Active-Area

The ability to compare, analyze, and interpret laboratory-scale experimental data for polymer electrolyte membrane fuel cells (PEMFCs) is often limited by differences in the performance between 25 cm2 and 50 cm2 active area cells. The present study includes the material of gas diffusion layers (GDL), their compression pressure, and the operating conditions to quantify and understand the effect of these factors on the performance of PEMFCs with different active area of electrodes. The experimental data show that under the same compression the internal compression pressure is higher for smaller cells compared to larger cells. Typically one assumes by increasing the compression pressure that the contact resistance is decreased and better performance is obtained. However, further increase of compression may cause mass transfer resistance inside of GDL due to the change of physical properties including pore size distribution.

Characterization of GDL for Water Transport in PEMFC Cathode

Water transport inside the porous media of the gas diffusion layer (GDL) plays an important role in the performance of fuel cells. Particularly in the cathode, the GDL must permit reactant gases to be transported from the flow channel to be distributed in the catalyst layer and also provide the pathway for the product water to be removed from the catalyst layer both as a gas and liquid phase. Water transport in the GDL depends on the characteristics of the porous media used. However, what is occurring within the GDL is difficult to describe and is still not completely understood.

Electrochemical Characterization of Various Carbon-Supported Pt-Pd Bimetallic Electrocatalysts Prepared by Electroless Deposition

Various Pt-Pd/C bimetallic compositions have been prepared by electroless deposition (ED) methods. The morphology has been identified as Pd cores partially encapsulated by Pt shells by various spectroscopic techniques. No monometallic Pt or Pd particles have been detected. The ratio of Pt to Pd was also well controlled. Although the electrochemical activity of the Pt-Pd/C catalyst for oxygen reduction reaction (ORR) was equal to or less than that for commercially available Pt/C catalysts, the amount of hydrogen peroxide detected as ring current was reduced by the exposed Pd component, suggesting that such a catalyst has the potential to decrease ionomer degradation in certain applications. The Pt on Pd/C catalysts also show much higher resistance to agglomeration induced by potential cycling. Analysis by high resolution scanning transmission electron microscopy following potential cycling reveals no changes in both particle sizes and electrochemical active areas.