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Silicon-based fuel cells are under active development for power generation for portable electronic devices. Previous work has demonstrated that an acid loaded nanoporous silicon membrane could be a suitable proton conducting material that is compatible with silicon microfabrication technology. In this design, the acid acts as an electrolyte while the porous silicon acts as a separator that limits fuel crossover. Unfortunately, the power output of the previous nanoporous-silicon based fuel cells was far below Nafion-based fuel cells. In this paper a new design for a nanoporous-silicon based miniature direct formic acid fuel cell is proposed and tested. The effects of the thickness, pore size, and formic acid concentration on the nanoporous silicon miniature fuel cell performance are studied. At room temperature in ambient air the fuel cell peak power density reached 94mW∕cm2 with a current density level of 314mA∕cm2 , using 5M formic acid fuel with 0.5M sulfuric acid electrolyte. This power output is three times higher than in previous work. These results show that the new design is a substantial improvement and that microfabricated silicon fuel cells using nanoporous silicon are potentially excellent power sources for portable electronic devices.

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The objective of this paper is to report the recent progress in the development of porous silicon fuel cells for micro power generation. Previous work has demonstrated that an acid loaded porous silicon membrane could be a suitable proton conducting material that is compatible with silicon microfabrication technology. In this paper, we present recent improvements to our previously published micro fuel cell designs that achieve 94 mW cm−2 at room temperature. In addition, a percolation model is shown to be suitable for understanding the proton transport mechanism in acid loaded porous silicon membranes.

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