Hydrogen production in Ar/NH/sub 3/ micro-discharges

Summary form only given. Microdischarges (MDs) are being investigated for a variety of applications including hydrogen production for portable fuel cells, microreactors and displays. In portable fuel applications, major system issues include development of practical and safe methods to produce H₂ with low lag-times. H₂ production from feedstock gases like NH₃ typically requires high gas temperatures for thermal decomposition. Due to their high power densities (>10s kW/cm^-3) MDs provide an intense source of electron impact dissociation as well as high gas temperatures (>1000 K) for thermal dissociation. By operating at pressures up to and including atmospheric, reformation of N₂ and H₂ from the dissociation products by three body reactions can be efficient. In this paper, results from a computational investigation of production of H₂ from atmospheric pressure microdischarges in Ar/NH₃ mixtures will be discussed. The computational platform is a 2-dimensional plasma hydrodynamics model having an unstructured mesh to resolve non-equilibrium electron, ion and neutral transport using fluid equations. Sheath accelerated, beam-like electrons are resolved using a Monte Carlo simulation. A compressible Navier-Stokes module provides the bulk fluid velocities and temperatures. The devices we investigated are cylindrically symmetric sandwich type reactors with characteristic dimensions of 100s mum at high pressures (few 100s torr to atmospheric). Results from a parametric investigation of power (up to 10s W), flow rates (residence time of a few mus) and Ar/NH₃ ratios will be discussed with the goal of maximizing the conversion of NH₃ to H₂ while minimizing the required power