Effect of Dopant Loading on the Structural and Catalytic Properties of Mn-Doped SrTiO3 Catalysts for Catalytic Soot Combustion

Abstract

Soot particles have been associated with respiratory diseases and cancer. To decrease these emissions, perovskite-mixed oxides have been proposed due to their thermal stability and redox surface properties. In this work, SrTiO 3 doped with different amounts of Mn were synthesized by the hydrothermal method and tested for soot combustion. Results show that at low Mn content, structural distortion, and higher O ads /O lat ratio were observed which was attributed to the high content of Mn 3+ in Ti sites. On the other hand, increasing the Mn content led to surface segregation of manganese oxide. All synthesized catalysts showed mesopores in the range of 32-47 nm. In the catalytic combustion of soot, the samples synthesized in this work lowered the combustion temperature by more than 100 • C compared with the uncatalyzed reaction. The sample doped with 1 wt % of Mn showed the best catalytic activity. The activation energy of these samples was also calculated, and the order of decreasing activation energy is as follows: uncatalyzed > Mn0 > Mn8 > Mn4 > Mn1. The best catalytic activity for Mn1 was attributed to its physicochemical properties and the mobility of the oxygen from the bulk to the surface at temperatures higher than 500 • C.

Catalytic Mechanism of Oxygen Vacancies in Perovskite Oxides for Lithium–Sulfur Batteries

“…As a variable valence transition metal ion, ion Mn exists in the +3 and +4 valence states, and the average valence is lower than the +4‐valence state of the metal ion Ti. [ 35 ] Therefore, doping the ion Mn into the B site of the ABO 3 ‐type perovskite STO 3 will increase the concentration of oxygen vacancies in the crystal lattice.…”

“…The refined results indicate that perovskites STO 3 , STMn 0.1 , STMn 0.2 , and STMn 0.3 have the same perovskite structure ( Fm ‐3 m ), and the unit cell volume after doping with Mn decrease from 59.95 to 59.05 Å 3 . This result is because the ion radius of Mn +3 (72 Å) and Mn +4 (67 Å) is smaller than that of Ti +4 (74 Å), [ 35 ] so the incorporation of Mn +3 /Mn +4 into Ti +4 sites will reduce the volume of the unit cell. The TEM image of the perovskite STMn 0.3 is shown in Figure 1b, where lattice fringes with a pitch of 0.275 nm are observed, corresponding to the (110) plane of the perovskite STMn 0.3 .…”

Fabrication of Mn-Doped SrTiO3/Carbon Fiber with Oxygen Vacancy for Enhanced Photocatalytic Hydrogen Evolution

“…As shown in Figure 9a, pure SrTiO 3 nanoparticles have an obvious characteristic absorption edge at 375 nm, while the light absorption property of SrTiO 3 @CF is significantly enhanced compared with pure SrTiO 3 , which mainly comes from the strong light absorption property of carbon fibers. Mn-SrTiO 3 @CF photocatalytic composite fibers have stronger light absorption property compared with SrTiO 3 @CF materials, because the doping of Mn reduces the band gap of the composite material and promotes the red shift of the light absorption boundary and the extension to visible light [37]. Mn-SrTiO 3 @CF and SrTiO 3 @CF materials have a significant change in the radian of the bottom of the light absorption edge, which is presumed to be because of the existence of oxygen vacancies in the material, reducing the band gap of the catalyst and further enhancing the light absorption property.…”

A Negative Effect of Niobium‐Doped Ceria on Soot Oxidation Activity‡

“…Catalysts have been developed by several synthesis techniques such as the co‐precipitation method 14, 18, 47–49, EDTA citrate complex method 25, 50, hydrothermal method 4, 51, 52, nitrate calcination method 53, and solution combustion synthesis 26. The EDTA citrate method and direct calcination (DC) are opted in the current study.…”