Hydrogen Supply Using Borohydride and Prototyping of a Miniature Fuel Cell by Sand Blasting

This paper describes two works on a miniature fuel cell for portable application: (1) Demonstration of the conceptual prototype of a borohydride fuel cartridge, and (2) Prototyping of a 4-cell-stacked miniature polymer electrolyte fuel cell (PEFC) by sand blasting. The borohydride fuel cartridge consists of aqueous solution of sodium borohydride (NaBH4), a catalyst for hydrolysis reaction of the fuel (BH4- + 2H2O → 4H2 + BO2-), and a hydrogen separation membrane of porous PTFE (polytetrafluoroethylene). The hydrogen separation membrane seals the fuel and reactant, securing users from their leakage. We confirmed the feasibility of this fuel cartridge by experiments. The miniature PEFC consists of two glass-based current collector plates, and a MEA (membrane electrode assembly) with cell interconnections and a gas seal. Four 7×7 mm single cells are placed in 27.5 mm square area, and electrically connected in series. The current collector plate was fabricated by photolithography and sand blasting, which are preferable for mass-production. The miniature PEFC was tested using hydrogen as fuel, and an output of 0.5 mW/cm2 was obtained from a single cell. Keywords : fuel cell, borohydride, portable device, sand blasting.