Au/Porous silicon-based sodium borohydride fuel cells

The Au/Porous silicon structure (Au/PS) was developed as hydrogen fuel cell. The use of a porous silicon filled with hydrochloric acid as a proton‐conducting membrane and thin gold film as a catalyst in Au/PS/Si fuel cell is demonstrated. The devices were fabricated by first creating 10–20 µm thick porous silicon layer by anodization etching in a standard silicon wafer and then depositing the gold catalyst film onto the porous silicon. Using sodium borohydride (NaBH4) solution as the fuel, generation of the open‐circuit voltage of 0.55 V and the fuel cell peak power density of 13 mW cm−2 at room temperature was achieved. Moreover production of hydrogen by evolution (out‐diffusion) of hydrogen from solid sodium borohydride during thermal annealing at 30–120°C was investigated. Data on the effective diffusion coefficient of the hydrogen in NaBH4 were determined from intensity changes of infrared vibration peaks of B–H bond (2280 and 3280 cm−1), as a result of thermal annealing of NaBH4 samples. The relatively high values of the diffusion coefficient of hydrogen, increasing from 1×10−6 cm2 s−1 to 2×10−4 cm2 s−1 suggest that a thermo‐stimulated evolution process can be used for producing hydrogen from NaBH4. Copyright © 2010 John Wiley & Sons, Ltd.