Fabrication of Miniature Silicon Wafer Fuel Cells Using Micro Fabrication Technologies

The fabrication of miniature silicon wafer fuel cells by micro-fabrication technologies and their performance evaluation are presented in this paper. Various thickness of Nafion membranes, such as Nafion 117, 115, and 112, were tested as electrolytes in a miniature single cell operating with dry H₂/O₂. Among these membranes, Nafion 112 (with the thinnest thickness) gave the best performance of 92.2 mW/cm² at 250mA/cm². In order to enhance the output voltage of the fuel cell, a miniature twin-fuel-cell was fabricated in series using two membrane-electrode-assemblies of Nafion 112 membrane sandwiched between two silicon substrates. The novel structure of the miniature twin-fuel-cell is that the electricity interconnect from the cathode of one cell to the anode of another cell is made on the same plane. The interconnect is fabricated by sputtering a layer of gold on the top of the silicon wafer. Silicon dioxide is deposited on the silicon wafer adjacent to the gold layer to prevent short-circuiting between the twin-cells. At ambient conditions, the measured peak power densities of the miniature twin-fuel-cell operating with H₂/O₂ and 1.5M methanol/O₂, are 190.4mW/cm² and 15.4mW/cm², respectively.