It is a major challenge to develop the low–temperature catalysts (LTC, <250 °C) with excellent efficiency and stability for selective catalytic reduction (SCR) of NO_x by NH₃ from stationary sources. Mn-based LTC have been widely investigated due to its various valence states and excellent redox performance, while the poisoning by H₂O or/and SO₂ is one of the severe weaknesses. This paper reviews the latest research progress on Mn-based catalysts that are expected to break through the resistance, such as modified MnO_x–CeO₂, multi-metal oxides with special crystal or/and shape structures, modified TiO₂ supporter, and novel carbon supporter (ACF, CNTs, GE), etc. The SCR mechanisms and promoting effects of redox cycle are described in detail. The reaction kinetics will be a benefit for the quantitative study of Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms. This paper also introduces the applications of quantum-chemical calculation using density functional theory to analyze the physic-chemical properties, explicates the reaction and poisoning mechanisms, and directs the design of functional catalysts on molecule levels. The intensive study of H₂O/SO₂ inhibition effects is by means of the combination analysis of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT), and the amplification of tolerance mechanisms will be helpful to design an excellent SCR catalyst.

Carbon monoxide (CO) is a dangerous poisonous air pollutant that greatly affects humans, plants, animals, and the environment. It is largely present in industrial flue gas, automobile exhaust gas, heavy traffic congestion, residences where wood is burned indoors, and natural sources like forest fires. To control it, a catalytic converter is mainly used for CO oxidation that is a feasible technology for the removal of CO. A wide variety of catalysts are used in catalytic converters, such as those based on noble metals, base metals, perovskite, spinel, hopcalite, and monel, among which hopcalite (CuMnOx) catalysts are economical, and show good thermal activity, selectivity and availability for low-temperature CO oxidation. A hopcalite catalyst is prepared by different methods, and preparation parameters such as shaking temperature and pH (8–11.5) have an impact on its activity. This article focuses on summarizing the reaction process of hopcalite catalysts in CO catalytic oxidation and the key factors influencing their activity as follows: appropriate promotors, supports, pre-treatment, and advanced preparation methods in the activity of a hopcalite catalyst toward CO oxidation. CO conversion was considerably higher than 100% at low temperature 50–125 °C with extra O₂ in the feed gas. In fact, hopcalite is known to be an easily available and highly active catalyst for the low-temperature (25 °C) low-cost, complete oxidation of CO. Promoters, supports, pre-treatment, and advanced preparation methods have been added to improve the activity and stability of a hopcalite catalyst in CO oxidation. Also, deactivation generally occurs here via the hopcalite catalyst undergoing sintering and fouling during CO oxidation. A change in the hopcalite catalyst might result in an improvement in its overall performance in converters in the future.

The synergistic effect of PdCu alloys on TiO₂ nanosheets expands the light-absorption range, improves the adsorption of CO₂ and H₂O, and accelerates photogenerated electron migration, resulting in an increased CH₄ yield with a selectivity of 98.7%.