The dependence of the activity of the (Ni 20 wt %-Mn 4 wt %)/SiO 2 catalyst on the treatment of its surface in glow-discharge oxygen, argon, and hydrogen plasmas was studied. Catalytic experiments were performed in a flow reactor and under static conditions in a vacuum. The highest activity was observed after catalyst treatment in an argon plasma. Glow-discharge plasma treatment changed the structure and number of active centers, which resulted in a change in the reaction mechanism. Ab initio quantum-chemical calculations were performed using the Hartree-Fock (UHF) method for the Ni5 cluster. The results substantiated the suggested that the active center contained the hydrogen atom. © 2008 Pleiades Publishing, Ltd.