MEMS methanol reforming system for micro PEM fuel cell power sources

Abstract

Microelectromechanical system (MEMS) is being introduced at the various research fields. In particular, MEMS technology is very useful in portable applications that is sensitive to weight and volume of the system. Analysis, fabrication and testing of MEMS methanol reforming system for micro fuel cell power sources are presented in this thesis. The reforming system has been a key issue for successful development of polymer electrolyte membrane fuel cell (PEMFC) that has grown a great attention as an ideal alternative for micro power source. This thesis presents the development of MEMS methanol reformer complete with a heat source. Three prototypes were fabricated using MEMS technologies integrated with catalyst coating processes that include precipitation method, wet impregnation, and slurry injection method. The performance of the fabricated reformers was measured in the various conditions and the optimal performance was sought. Membrane separation and preferential oxidation were performed to remove carbon monoxide from the reformate gas. Integrated tests of the MEMS reformer with a micro fuel cell were carried out. First, a catalytic microreactor for hydrogen production was fabricated on photosensitive glasses. Microchannels with high tight tolerance and high aspect ratio were realized by anisotropic wet etching process of the glass. Cu/ZnO was selected as a catalyst for methanol-steam reforming and was prepared by co-precipitation method. The prepared catalyst particles were coated on the surface of microchannels using a precipitation method, resulting in the robust and uniform catalyst layer with the thickness of $30 \mu m$. Overall microfabrication process was established for a MEMS-based catalytic microreactor. The fabricated reactor has the volume of 1.8 $cm^3$ including the volume of reaction chamber of $0.3 cm^3$, and produced dry reformate with high hydrogen content of 73%. The hydrogen flow was 4.16 ml/min which can generate power output of 350 m$W_...