Optimization of H$_{2}$ Production in Ar/NH$_{3}$ Micro-discharges

Hydrogen powered vehicles and portable fuel cells may require real-time generation of H$_{2}$ to provide fuel safely and with rapid response. One such method is to produce H$_{2}$ from feedstock gases that can be more safely stored, such as NH$_{3}$. Microdischarge plasmas are being investigated as a means of H$_{2}$ production from NH$_{3}$ and other gases. The high power densities (10s kW/cm$^{3})$ that can be obtained in microdischarges provide an intense source of electron impact as well as thermal decomposition of the feedstock gases. By operating at high pressures ($>$ 100s Torr), reformation of the dissociated products leads to efficient production of H$_{2}$. In this work, results from a computational investigation of production of H$_{2}$ in high pressure microdischarges sustained in Ar/NH$_{3}$ mixtures will be discussed. Plug-flow and 2-dimensional plasma hydrodynamics models were used to develop scaling laws to optimize the energy efficiency of the process (e.g., eV/H$_{2}$ molecule produced). The 2-d model resolves non-equilibrium electron, ion and neutral transport using fluid equations. The microdischarge geometry of interest is a sandwich flow-through reactor with a central hole a few hundred microns in diameter, power of a few W and residence times of a few microseconds.