| Summary: | Co<sub>4−i</sub>Zn<sub>i</sub>MnAlO<sub>x</sub> mixed oxides (<i>i</i> = 0, 0.5 and 1) were prepared by coprecipitation, subsequently modified with potassium (2 or 4 wt.% K), and investigated for direct catalytic NO decomposition, one of the most attractive and challenging NO<sub>x</sub> abatement processes. The catalysts were characterised by atomic absorption spectroscopy, powder X-ray diffraction, Raman and infrared spectroscopy, temperature-programmed reduction by hydrogen, the temperature-programmed desorption of CO<sub>2</sub> and NO, X-ray photoelectron spectroscopy, scanning electron microscopy, the work function, and N<sub>2</sub> physisorption. The partial substitution of cobalt increased the specific surface area, decreased the pore sizes, influenced the surface composition, and obtained acid-base properties as a result of the higher availability of medium and strong basic sites. No visible changes in the morphology, crystallite size, and work function were observed upon the cobalt substitution. The conversion of NO increased after the Co substitution, however, the increase in the amount of zinc did not affect the catalytic activity, whereas a higher amount of potassium caused a decrease in the NO conversion. The results obtained, which were predominantly the acid-base characteristics of the catalyst, are in direct correlation with the proposed NO decomposition reaction mechanisms with NO<sub>x</sub><sup>−</sup> as the main reaction intermediates.
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