Advances in De-NO_x Methods and Catalysts for Direct Catalytic Decomposition of NO: A Review

China is the country with the most coal-power generation and the most diesel vehicles in the world; it is of great significance to research the reduction of NO emissions. This paper summarizes five de-NO_x methods, including adsorption, storage reduction, selective catalytic reduction, selective non-catalytic reduction, and direct catalytic decomposition, and explores the current research state and problems existing in actual application of each method. The direct catalytic decomposition method is focused especially, and research progresses of six major catalysts used in this method are summarized, including noble metals, metal oxides, perovskite-type composite oxide, hydrotalcite materials, heteropoly acid, and Cu–ZSM-5. The activity and O₂ tolerance of each catalyst are compared, and future research directions are given. Cu–ZSM-5 is studied in detail as a result of its high activity and O₂ tolerance and reviewed from three aspects, including the influence of preparation and reaction conditions on activity, the mechanism of catalytic decomposition, and doping modification. Finally, the future research directions of NO decomposition are discussed.