Hydrogen sulfide (H2S) dissociation into hydrogen and sulfur has been studied in a pulsed corona discharge reactor (PCDR). Due to the high dielectric strength of pure H2S (similar to 2.9 times higher than air), a nonthermal plasma could not be sustained in pure H2S at discharge voltages up to 30 kV with our reactor geometry. Therefore, H2S was diluted with another gas with lower dielectric strength to reduce the breakdown voltage. Breakdown voltages of H2S in four balance gases (Ar, He, N-2, and H-2) have been measured at different H2S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H2S and the balance gas. With increasing H2S concentrations, H2S conversion initially increases, reaches a maximum, and then decreases. H2S conversion and the reaction energy efficiency depend on the balance gas and H2S inlet concentrations. H2S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N-2 and H-2. These observations can be explained by proposed reaction mechanisms of H2S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H2S into hydrogen and sulfur. (c) 2007 Elsevier Ltd. All rights reserved.