Shohji Tsushima

Two-Stage Degradation of PEMFC Performance Due to Sulfur Dioxide Contamination

Accelerated degradation tests of a PEMFC due to SO2 poisoning were performed to investigate time-evolutional process of the cell performance. It was revealed that SO2 contamination in the cathode air stream caused either one-stage or two-stage degradation of the PEMFC performance, which depends on cell operating condition. Partial recovery of the cell voltage indicated that weak (reversible) absorption and strong (irreversible) absorption of SO2 are involved in the contamination process by SO2 in the electrode. Experimental observation on two-stage degradation depending on the cell voltage suggested a formation of a sulfur monolayer followed by a multilayer formation of sulfur on the catalyst in the two-stage degradation of the PEMFC.

Performance Improvement in Redox Flow Battery With Flow-Through Channel Geometry

Redox Flow battery attracts much attention as one of the efficient rechargeable batteries because of its versatility for small and large scale energy storage. Although this battery has great potentials, further improvement on cell performance to achieve high current density is necessary for industrial implementation. In this study, we applied flow-through (interdigitated) channel geometry to a redox flow battery for enhancement of electrode utilization by advection transport. As a result, it is confirmed that the redox flow battery showed better performance by using interdigitated channels than ones with serpentine channels.Copyright

Water Management and Experimental Diagnostics in Polymer Electrolyte Fuel Cell

Polymer electrolyte fuel cell (PEFC) is a promising candidate for mobile and vehicle applications and distributed power systems because of its high power density and low operating temperature. However, there are several technical problems to be solved in order to achieve practicability and popularization. Especially, water management inside a PEFC is essential for high performance operation. At high current densities, excessive water generated by the electrode reaction is rapidly condensed in the cathode electrode. When the open pores in the catalyst layer (CL) and gas diffusion layer (GDL) are filled with liquid water, oxygen cannot be supplied to the reaction sites. Furthermore, water migrates significantly through the electrolyte membrane from the anode to cathode owing to electroosmotic drag. Thus, the membrane dehydration occurs mainly on the anode side and causes the low proton conductivity during low-humidity operation. These phenomena known as “water flooding” and “dryout” are a critical barrier for high efficiency and high power density. To alleviate these issues, it is necessary to develop various diagnostic tools for understanding the fundamental phenomena of water transport between cathode and anode in PEFC.