Combination of\nPlasma Jet and Magnetron SputteringA\nNew Method for Preparing Thin Ni–Co–Mn Oxide Coatings\non Stainless Steel Meshes and Their Efficiency in the Total Oxidation\nof Volatile Organic Compounds

For the first time,\nternary Ni–Co–Mn oxide catalysts\nwere prepared by a combination of sputtering techniques. Thin coatings\nof Ni–Co–Mn oxides were deposited on stainless steel\nmeshes by using a new method that involved a combination of plasma\njet sputtering from a hollow Ni–Co cathode and simultaneous\nmagnetron sputtering of manganese. The resulting thin-film catalysts\nare suitable for various oxidation reactions such as total oxidation\nof volatile organic compounds. The catalysts with a Ni/Co molar ratio\nof 1:1 and varying amounts of Mn were compared with the binary Ni–Co\noxide catalyst in terms of their ability to oxidize ethanol and toluene.\nThe powder X-ray diffraction showed spinel-type mixed oxides and NiO-like\noxides in the oxide coatings. The TPR profiles revealed easier reducibility\nof the Ni–Co–Mn oxides compared with that of the Ni–Co\noxide and the synergistic effect of Mn addition. The Ni–Co–Mn\noxide catalysts exhibited higher catalytic activity than the binary\ncatalysts due to mixed oxide phases with disordered structure and\nthe presence of Mn<sup>4+</sup>. The catalysts showing the highest\nactivity in the oxidation of ethanol and toluene were prepared at\na low plasma jet energy input and a high magnetron sputtering energy\ninput. The thin-film catalysts prepared by this method have a primary\nadvantage over pelletized catalysts due to their extremely low contents\nof active Ni, Co, and Mn oxides in the catalyst bed and negligible\ninternal diffusion effects. The proposed novel method of plasma sputtering\nof Ni and Co components from a hollow cathode, combined with simultaneous\nmagnetron sputtering of Mn, has potential for industrial application.\nIt allows the preparation of ternary catalysts that are more active\nthan the previously reported binary catalysts. Moreover, the preparation\nprocedure can be applied to other transition metal oxides, not just\nNi–Co–Mn.