Designing, manufacturing, testing, and optimizing of micro-fuel cells

Micro-fuel cells are considered as promising electrochemical power sources in portable electronic devices. Performance of micro-fuel cells are closely related to many factors, such as processes of fabrication, designs of flow fields, and operating conditions. In the present research, micro-proton exchange membrane fuel cells (PEMFCs) and micro-direct methanol fuel cells (DMFCs) were systematically investigated from the aspects of structure design, bipolar/end plates (BPs) fabrication, and fuel cells evaluation.;In chapter 3, compared with conventional machining and rapid prototyping (RP) technology, microelectromechanical system (MEMS) technology was the practicable method to fabricate the BPs with channels of a few microns width.;Experimental and modeling methods were employed to analyze performance of the micro-PEMFC in chapter 4. Contact resistance changed significantly the distribution of overpotential in the micro-PEMFC and decreased the current output. Small dimensions of the micro-channel drastically affected the species transport and resulted in a non-uniform current distribution along channel direction at low cell potential (high current).;In chapters 5, four kinds of flow fields, mixed multichannel serpentine with wide channels, single channel serpentine, double channel serpentine, and mixed multichannel serpentine with narrow channels, were applied to micro-PEMFCs. Results suggested that the micro-PEMFC with good performance should use the flow field with a mixed multichannel design and long micro-channels.;In chapter 6, the same flow fields were studied in the micro-DMFCs. Concentration and flow rates of methanol solution affected performance of micro-DMFCs. A micro-DMFC with the long and narrow channels needed to take long time to reach the stable stage when an electric load on it was changed.;In chapter 7, a passive air-breathing micro-DMFC with low loading of catalysts was developed. Performance of the passive micro-DMFC became poor with the increase in concentration of methanol solution. Power densities of the passive micro-DMFC drastically depended on the current scanning rate.;Finally, cobalt phthalocyanine was introduced to platinum catalyst system to improve and optimize the micro-DMFCs. After heat-treatment at 635°C, CoPc-Pt/C demonstrated good electrocatalytic activity for oxygen reduction reaction (ORR) and high methanol tolerance. However, CoPc-Pt/C heated at 980°C showed a good electrocatalytic activity for MOR in DMFCs.