A novel pulsed corona wire-in-tube reactor with quartz view-ports allowed visual observation of the effect of charge voltage and gas composition on the corona distribution. The H2S conversion and energy efficiency of H2S decomposition in this pulsed corona discharge reactor varied at constant power (100W) due to the selected values of the electrical parameters of pulse forming capacitance (720-2880 pF), charge voltage (11-21 kV), and pulse frequency (157-961 Hz). Low pulse forming capacitance, low charge voltage, and high pulse frequency operation produces the highest energy efficiency for H2S conversion at constant power. H2S conversion is more efficient in Ar-N-2 gas mixtures than in At or N-2. These results can be explained by corona discharge observations, the electron attachment reactions of H2S at the streamer energies, and a proposed reaction mechanism of H2S dissociation in the Ar-N-2 gas mixture. The energy consumption per molecule of converted H2S in an equimolar mixture of At and N-2 (4.9eV/H2S) is the lowest that has been reported for any plasma reactor operated at non-vacuum pressures. The results reveal the potential for energy efficient H2S decomposition in pulsed corona discharge reactors. (C) 2009 Elsevier Ltd. All rights reserved.