H2 generation in Ar/NH3 microdischarges

Due to the difficulty of H-2 storage, development of real time H-2 generators would be advantageous for portable fuel cells. In this paper, the real time production of H-2 using microdischarge devices is discussed with results from a computational investigation. Ar/NH3 mixtures were studied using plug flow and two-dimensional models. Dissociation of NH3 by electron impact and thermal processes produces H atoms which recombine to form H-2. We found that for sandwich type microdischarges with a diameter of 300 mu m, dissociation of NH3 is approximately 95% by electron impact and 5% by thermal processes for a NH3 mole fraction of 5%. Efficiency of conversion of NH3 to H-2 is dependent on residence time in the discharge, mole fraction and geometry, as these properties determine the eV/molecule deposited into NH3. Conversion efficiencies (fraction of H in NH3 converted to H-2) in excess of 83% are predicted for optimum conditions.