Investigation of hydrogen production from boron compounds for PEM fuel cells

This paper presents a comprehensive study of hydrogen production from sodium borohydride (NaBH4), which is synthesized from sodium tetraborate (Na2B4O7) decomposition, for proton exchange membrane (PEM) fuel cells. For this purpose, Na2B4O7 decomposition reaction at 450-500 degrees C under hydrogen atmosphere and NaBH4 decomposition reaction at 25-40 degrees C under atmospheric pressure are selected as a common temperature range in practice, and the inlet molar quantities of Na2B4O7 are chosen from 1 to 6 mol with 0.5 mol interval as well. In order to form NaBH4 solution with 7.5 wt.% NaBH4, 1 wt.% NaOH, 91.5 wt.% H2O, the molar quantities of NaBH4 are determined. For a PEM fuel cell operation, the required hydrogen production rates are estimated depending on 60, 65, 70 and 75 g of catalyst used in the NaBH4 solution at 25, 32.5 and 40 degrees C, respectively. It is concluded that the highest rate of hydrogen production per unit area from NaBH4 solution at 40 degrees C is found to be 3.834 x 10(-5) g H-2 s(-1) cm(-2) for 75 g catalyst. Utilizing 80% of this hydrogen production, the maximum amounts of power generation from a PEM fuel cell per unit area at 80 degrees C under 5 atm are estimated as 1.121 W cm(-2) for 0.016 cm by utilizing hydrogen from 75 g catalyst assisted NaBH4 solution at 40 degrees C. (c) 2005 Elsevier B.V. All rights reserved.