Abstract
With the aim of dramatically reducing CO2 emissions from automobiles, we are developing both electric vehicles (EVs) and fuel cell vehicles (FCVs) as zero emission vehicles. Research and development work on Nissan FCVs has been under way since 1996. The main issues that must be addressed to commercialize FCVs include: (1) to prevent performance decay, (2) to increase power density, (3) to improve subzero start-up capability, and (4) to develop technologies for reducing costs. Fundamental research activities undertaken to resolve these issues have elucidated various phenomena such as the mass transportation mechanism and degradation mechanism in the membrane electrode assembly (MEA) and corrosion on metal bipolar plates. These activities have resulted in the accumulation of the following technologies and results: (1) a method of estimating performance decay, (2) a surface treatment technology for corrosion-proofing metal bipolar plates, (3) verification of improved subzero start-up capability, and (4) MEA specifications for high current density operation with low cathode humidity.
These technologies have been incorporated in a new Nissan fuel cell stack that achieves a power density of 1.9 kW/L (130 kW/68 L) and a lower cost by reducing the amount of Pt catalyst used by one-half compared with the previous stack model. The performance and durability of the new stack are close to satisfying the requirements for real-world use, except the cost. One effective approach to reducing the cost is to lower the amount of Pt catalysts used further such as by using Pt more effectively. Toward that end, it is important to further analyze the reaction and physical transport mechanisms taking place at the electrode catalyst layer.
This paper presents the results achieved to date and describes various activities under way to address the four main issues mentioned above.
Keywords: Fuel Cell Vehicle, Performance Decay, Power Density, Subzero Start-up, Reducing Cost