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Mn-based catalysts have attracted significant attention in the field of catalytic research, particularly in NOx catalytic reductions and CO catalytic oxidation, owing to their good catalytic activity at low temperatures. In this review, we summarize the recent progress of Mn-based catalysts for the removal of NOx and CO. The effects of crystallinity, valence states, morphology, and active component dispersion on the catalytic performance of Mn-based catalysts are thoroughly reviewed. This review delves into the reaction mechanisms of Mn-based catalysts for NOx reduction, CO oxidation, and the simultaneous removal of NOx and CO. Finally, according to the catalytic performance of Mn-based catalysts and the challenges faced, a possible perspective and direction for Mn-based catalysts for abating NOx and CO is proposed. And we expect that this review can serve as a reference for the catalytic treatment of NOx and CO in future studies and applications. [ABSTRACT FROM AUTHOR]

The effects of four distinct zinc species (ZnCl2, Zn(NO3)2, ZnSO4, and ZnCO3) on a Mn-Ce co-doped CuX (MCCX)catalyst were investigated and contrasted in the low-temperature NH3-SCR process. Aqueous solutions of ZnCl2, Zn(NO3)2, ZnSO4, and ZnCO3 were used to poison the catalysts. The catalytic activity of all catalysts was assessed, and their physicochemical properties were studied. There was a notable drop trend in catalytic activity in the low temperature range (200 °C) after zinc species poisoning on MCCX catalyst. Interestingly, ZnSO4 and ZnCO3 on MCCX catalyst had more serious effect on catalytic activity than Zn(NO3)2 and ZnCl2 from 150 °C to 225 °C, in which NO conversion of the MCCX-Zn-S and MCCX-Zn-C catalysts dropped about 20–30% below 200 °C compared with the fresh MCCX catalyst. The zeolite X structure was impacted by Zn species doping on the MCCX catalyst, and the Zn-poisoned catalysts had less acidic and lower redox ability than fresh Mn-Ce/CuX catalysts. Through the results of in situ DRIFTS spectroscopy experiments, all catalysts were governed by both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms, and the possible mechanism for poisoning the Mn-Ce/CuX catalyst using various zinc species was revealed. [ABSTRACT FROM AUTHOR]

In this study, a series of zeolite-X-supported different crystal phases of MnO2 (α-MnO2, β-MnO2, γ-MnO2, and σ-MnO2) catalysts were prepared via a solid-state diffusion method and high-heat treatment method to explore their low-temperature NH3-SCR performance. All of the catalysts featured typical octahedral zeolite X structures and manganese dioxides species of various crystal types dispersed across the support surface. Throughout the entire temperature range of the reaction, γ-MnO2/X catalyst had the highest NO conversion. Additionally, β-MnO2/X, γ-MnO2/X, and σ-MnO2/X catalysts had nearly 100% of N2 selectivity, whereas the α-MnO2/X catalyst had the lowest N2 selectivity (about 90%) below 125 °C. Moreover, the γ-MnO2/X catalyst demonstrated superior acidity capacity and reduction ability compared with the other three catalysts. All the catalysts contained the essential intermediates NH2NO and NH4NO3 species, which are essential to the SCR reaction. More acid sites and nitrate species existed on the γ-MnO2/X catalyst than on the other catalysts, thereby boosting the SCR reaction. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have been explored as a surface modification strategy to promote the oxygen reduction reaction (ORR) on Pt/C and their chemical structures were identified to have strong influence on the ORR activities. To better understand the roles of anion and cation of ILs on the catalytic reaction, two cations ([MTBD]+ and [bmim]+) were paired with three anions ([TFSI]−, [beti]−, and [C4F9SO3]−) to form various IL structures. By systematically varying the IL combinations and studying their effects on the electrochemical behaviors, such as electrochemical surface area and specific ORR activities, it was found that cation structure had a higher influence than anion, and the impact of the [MTBD]+ series was stronger than the [bmim]+ series. In addition to the investigation in the half-cell, studies were also extended to the membrane electrode assembly (MEA). Considerable performance enhancements were demonstrated in both the kinetic region and high current density region with the aid of IL. This work suggests that IL modification can provide a complementary approach to improve the performance of proton exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

In this study, the poisoning effect of CaO on activated carbon (AC)-based Mn-Ce catalysts was discussed. Loading CaO inhibited the catalytic activity of the catalyst and the NO conversion of the catalyst decreased from 69.5% to 38.2% at 75 °C. The amount of MnO2 in AC surface decreased in the process of loading CaO, which was detrimental to the Selective Catalytic Reduction (SCR) performance of the catalyst. The change of manganese oxide form inhibited generation rate for the chemisorption oxygen and NO2, which was the most critical reason for the decrease of catalytic activity. Besides, loaded CaO entered into the pores of the catalyst, which led to the blockage of the pores and further resulted in the decrease of the Brunauer-Emmett-Teller (BET) surface area and total pore volume. It also destroyed the oxygen-containing functional groups and acid site on the surface of AC. All of these caused the deactivation of Mn-Ce/AC catalyst after loading CaO. [ABSTRACT FROM AUTHOR]