The breaking of the C-S bond in C2H5SH on the catalytically active (100) edge of 2H-MoS2 was studied by means of density functional theory. Two reactions Of C2H5SH were investigated: hydrogenolysis to ethane and elimination to ethane, with H2S as second product in both cases. The adsorption geometry, involving a hydrogen atom of the methyl group Of C2H5SH, conducted reactions to more strongly bound surface intermediate states. The C-S bond breaking resulting in ethane formation proceeds with a lower energy barrier than in ethene formation when the energy of the barriers for desorption of the products from the surface is compared relative to the molecularly adsorbed C2H5SH state. (c) 2006 Elsevier Inc. All rights reserved.