A self-breathing proton-exchange-membrane fuel-cell pack with optimal design and microfabrication

An entire set of silicon-based microtechnologies is developed for a high-performance H-2/air self-breathing microproton-exchange-membrane fuel-cell (mu PEMFC) pack. For improving the performance of the silicon-based mu PEMFC, microflow-fields together with the electrodes at the cathode and the anode are optimally designed. For simplifying the microfabrication, a bulk-micromachining process is developed for fabricating both the cathode and the anode. Besides that the optimally designed flow-fields and electrodes are accurate fabricated, both the cathodes and the anodes can be fabricated in a same wafer with identical process. Optimized packaging conditions, such as the compression ratio and the current-collecting layer for the membrane electrode assembly (MEA), are experimentally obtained for both high fuel-cell performance and reliable silicon micropackaging. Attributed to the optimized design and the precise microfabrication, the peak power-density of the self-breathing mu PEMFC is measured as high as 141.0-147.2 mW/cm(-2). For adapting the output voltage to handheld electronic systems, a thin-pad planar configuration is designed for the mu PEMFC pack that consists of six single cells connected in series. The planar-configured self-breathing mu PEMFC pack is micropackaged on a silicon-micromachined base-chip, with the specific power as high as 271 mW/cm(3) measured. Experimental results demonstrate that the fuel cells can reliably work under normal environmental temperature and humidity. 1200-h continuing power supply of the mu PEMFC pack is performed, resulting in stable output of about 3 V.