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The anions of precipitants played a leading role in the formation of catalytic phase while the cations decided the stability of hydroxyl group and further altered the morphology of catalysts. That was why the ammonium and sodium hydroxide possessed the similar hydroxyl group and amorphous MnFe composition, they still presented the different surface structure features. The coupling behavior of active precursors under different precipitants was the root cause of internal motivation of catalytic properties. [Display omitted] • Anion and cation of precipitant served in phase transition and structure features. • Reactants activation of precipitants acted as the inherent motivation of activity. • Precipitant affected the catalyst intrinsic activity deeply by kinetic analysis. • Possible inductive mechanism model of three precipitants on catalyst was proposed. Herein, the inductive strategy of three precipitants on dual transition metal MnFeO x catalysts for low-temperature NH 3 -SCR reaction was investigated in detail. The results showed that the anions of precipitants played the leading role in the formation of catalytic phase, in which carbonate induced the transfer of Mn precursor from MnCO 3 to the ultimate Mn 2 O 3 phase while that of hydroxyl from Mn 3 O 4 to Mn 5 O 8 phase. Iron coupling would alter the original transition behavior of manganese due to an internal synergistic effect. Furthermore, the cations decided the stability of hydroxyl groups on ammonium and sodium hydroxide precipitants, leading to the difference of morphology in catalysts. The activity results suggested that MnFe-ammonium carbonate (denoted as AC) catalyst possessed the higher catalytic efficiency than other catalysts, with over 90% NO conversion achieved from 75 to 225 °C. The abundant Mn4+ and Fe3+ and strong surface acidity of MnFe-AC catalyst were in favor of the redox circle and the adsorption of NH 3. Both activation energy and TOF, relied on the amount of acid, confirmed that the precipitants had an effect on the intrinsic catalytic activity of the catalysts such as energy barrier and reaction rate. Transient reaction further revealed that both E-R and L-H mechanisms co-existed on all catalysts, while E-R mechanism contributed more during the SCR process. On this basis, the possible inductive mechanism model of three precipitants on MnFeO x catalyst was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sm-doping strengthened NH 3 -SCR activity and SO 2 tolerance over MnFeO x catalyst. • Enhanced NO 2 cooperated with increased NH 3 (ads) to cause "Fast SCR" reaction. • Sm induced Fe serving as sacrificial sites to preferentially react with SO 2. • Mechanism model for improving activity and SO 2 tolerance with Sm was proposed. The development of catalysts with high NH 3 -SCR activity in the presence of SO 2 was urgent for non-electric industries to control NO x emission at low temperature. Herein, a series of Sm-doping MnFeO x catalysts were synthesized through a typical PEG-assisted co-precipitation method and applied for low-temperature NH 3 -SCR process. SmMnFe-0.1 catalyst significantly broadened the activation temperature window and yielded almost 100% NO conversion from 75 to 200 °C, simultaneously, the NO removal efficiency still maintained at about 90% in the presence of SO 2 and H 2 O. The characterization results confirmed that Sm could optimize the dispersity of active components and enlarge the surface area of catalyst. Furthermore, strong interaction among active ions facilitated more oxygen vacancies and accelerated NO oxidizing to NO 2 , further cooperating with abundant adsorbed NH 3 , leading to cause "Fast SCR" reaction. Both catalysts were dominated by the E-R mechanism despite MnFeO x catalyst also obeyed the L-H pathway. Particularly, the intense redox circles between Sm and Mn inhibited the electron transferring from SO 2 to Mn ions, and induced Fe species serving as sacrificial sites along with Sm to preferentially react with SO 2 , resulting in an excellent SO 2 tolerance, and the possible mechanism model was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • CuO modified CeFe catalysts were prepared via wet impregnation method. • CuO could improve de-NO x and CO oxidation activities for CeFe catalyst. • CuO could increase surface acidity, Ce3+/(Ce3+ + Ce4+) ratio and surface adsorbed oxygen of CeFe catalyst. • Reaction mechanism model of CuO over CeFe catalyst for NH 3 -SCR and CO oxidation was proposed. Nitrogen oxides (NO x) and carbon monoxide (CO) coexisted in numerous industrial waste gases. And selective catalytic reduction of NO x with ammonia (NH 3 -SCR) and CO catalytic oxidation were considered as the effective technologies for simultaneous elimination of NO x and CO, respectively. However, an efficient bifunctional catalyst was crucial for achieving simultaneous removal of NO x and CO. Herein, we developed a series of Cu-modified CeFe catalysts for simultaneous removal of NO x and CO. The results demonstrated that 5Cu-CeFe catalyst presented the best catalytic performance, achieving approximately 81% NO x removal efficiency and nearly 99% CO conversion rate at 200 °C under a gas houely space velocity of 90,000 h−1. The XPS analysis demonstrated that copper oxides played a critical role in promoting the formation of Ce3+ and O β , thereby facilitating the NH 3 -SCR catalytic performance and CO catalytic oxidation. Moreover, the copper oxide modification of CeFe catalyst attained a trade-off between the surface acidity and redox ability, resulting in improving adsorption and activition capacity of the reactant gases. In situ DRIFTS experiments revealed that the NH 3 -SCR process primarily obeyed the Eley-Rideal (E-R) pathway over both CeFe and 5Cu-CeFe catalysts, while Langmuir-Hinshelwood (L-H) pathway hardly participated in NH 3 -SCR process. The presence of Cu+–CO species and surface lattice oxygen was crucial for CO oxidation, and both Mars-van Krevelen (M−K) and L-H pathways might be involved in the CO catalytic oxidation process over 5Cu-CeFe catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn and/or Ce doping on blast furnace slag-derived zeolite X catalysts were firstly synthesized. • Mn-Ce/X catalyst had the highest NO conversion and the best N 2 selectivity. • Mn-Ce/X catalyst had higher Mn4+/Ce3+, stronger acidity and excellent redox ability. • NH 2 NO and NH 4 NO 2 intermediates on Mn-Ce/X catalyst prevented the generation of N 2 O. Several Mn and/or Ce oxides on blast furnace slag-derived (BFS-derived) zeolite X catalysts were prepared to investigate their low-temperature NH 3 -SCR performance. It was found that Mn-Ce/X catalyst had the highest NO conversion of nearly 98% at 250 °C and excellent N 2 selectivity of nearly 100% during 75–175 °C. The co-addition of Ce and Mn could inhabit the growth of crystal grains, resulting in the increase of surface area and the generation of Mn-Ce double active sites. Besides, high concentration of Mn4+ and Mn3+ could promote oxidation of NO to NO 2 accelerating the "fast-SCR" reaction and high concentration of Ce4+ could form more oxygen vacancies on Mn-Ce/X catalyst. In addition, the Mn-Ce/X catalyst had large acid amount and high redox ability owing to the co-existed Mn-Ce double active sites on zeolite catalyst and the co-effect of Mn-Ce oxides and zeolite X. Furthermore, the decomposition of NH 4 NO 3 species on Mn/X catalyst led to the low N 2 selectivity at higher temperature. While NH 2 NO and NH 4 NO 2 intermediates on Mn-Ce/X catalyst played a vital part in NH 3 -SCR reaction and prevented the generation of N 2 O, and Mn-Ce/X catalyst provided more Mn-Ce active sites for the reaction between NO 3 – species and gaseous NO, accelerating SCR catalytic reaction. [ABSTRACT FROM AUTHOR]

• Synergistic interaction of Sm and Fe enhanced Pb-resistance of Mn-Ce/AC catalyst. • Sm and Fe co-doping alleviated the damage of Pb species to catalyst structure. • Surface acidity and redox ability of Mn-Ce/AC catalyst were protected by Sm and Fe from lead. • NH 3 -SCR reaction on catalysts after Pb poisoning followed L-H and E-R mechanism. A novel anti-Pb poisoning Sm and Fe co-doped Mn-Ce/AC catalyst was prepared by impregnation method for low-temperature NH 3 -SCR of NO reaction. Maintaining the excellent low-temperature activity of Mn-Ce/AC catalyst, Sm and Fe co-doping remarkably enhanced the catalyst's Pb-resistance with NO conversion up to 77%. Sm and Fe co-doped poisoning-catalysts exhibited large specific surface area and pore volume, and the crystallinity of the MnO x and CeO x reduced. The redox properties and surface acidity of the lead poisoned SmFeMnCe/AC catalyst were effectively retained, which could promote NO oxidation and NH 3 activation, further benefiting the SCR reaction. In situ DRTFTS results indicated that the low-temperature NH 3 -SCR mechanism of all poisoned catalysts followed both L-H mechanism and E-R mechanism, and the L-H mechanism was dominated. On the one hand, the extraordinary lead resistance of Sm weakened the damage of lead species on the physicochemical properties of the catalyst; on the other hand, the high oxidation properties and surface acidity of Fe enhanced the catalytic activity of the poisoned catalyst. Finally, a possible synergistic mechanism model of Sm and Fe co-doping on Mn-Ce/AC catalyst against Pb-poisoning was proposed. [ABSTRACT FROM AUTHOR]