Constructing a Pt/YMn₂O₅ Interface to Form Multiple Active Centers to Improve the Hydrothermal Stability of NO Oxidation

Abstract

The hydrothermal stability of NO oxidation is the key to the practical application of diesel oxidation catalysts in diesel engines, which in the laboratory requires that NO activity does not decrease after aging for 10 h with 10% H 2 O/air at 800 °C. On the one hand, the construction of a metal/oxide interface can lead to abundant oxygen vacancies (O v ), which compensate for the loss of activity caused by the aggregation of Pt particles after aging. On the other hand, YMn 2 O 5 (YMO) has excellent thermal stability and NO oxidation capacity. Therefore, a Pt/YMn 2 O 5 -La-Al 2 O 3 (Pt/ YMO-LA) catalyst was prepared by the impregnation method. The support of the catalyst, YMn 2 O 5 -La-Al 2 O 3 (YMO-LA), was obtained by mixing high specific surface LA and YMO ball-milling. Under laboratory-simulated diesel exhaust flow, the NO oxidation performance of Pt/YMO-LA did not decrease after hydrothermal aging. Combining high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and oxygen temperature-programmed desorption (O 2 -TPD), the Pt/YMn 2 O 5 interface was formed after hydrothermal aging, and the increased O v can provide reactive oxygen to Pt and YMO. The cooperative catalysis of multiple active centers composed of Pt, YMO, and O v is the crucial factor to maintain the NO oxidation performance. In addition, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) show that an increase in O v is beneficial to the adsorption and desorption of more nitrate and nitrite intermediates, thus achieving the hydrothermal stability of NO oxidation.

Unidirectional Electron Transfer on Bismuth-Doped Pt/YMn2O5 for Efficient CO Oxidation as Diesel Oxidation Catalysts

“…After hydrothermal aging, the surface Pt 0 content of all catalysts decreased, which is mainly attributed to the relative decrease in surface Pt content due to the aggregation of Pt particles, which is a similar phenomenon in previous studies. 23 Meanwhile, the Pt 0 content fitted from the Pt 4d spectra is consistent with the Pt 0 peak area near 70.9 eV in the Al 2p spectrum. In conclusion, the above results demonstrate, to some extent, the existence of Pt−O−Bi specific structures.…”

“…Notably, based on the high-resolution transmission electron microscopy (HRTEM) of Figures 3b and S9, it can be recognized that all catalysts have significant Pt/mullite interfaces, and the NO oxidation reaction by the participation of the interfacial oxygen vacancies (O v ) is the key factor for the catalysts to possess hydrothermal stability, which is in line with the previous work. 23,24 In addition, the corresponding EDS results for the catalysts doped with bismuth elements also showed that there is a high degree of consistency in the spatial distribution of Pt and bismuth elements and no significant segregation phenomenon or obvious core−shell structure is observed. 36 This is sufficient to suggest that there is some interaction between the Pt and bismuth elements.…”

“…It is noteworthy that even after hydrothermal aging, the maximum NO conversion of all YMO mullite-containing catalysts reached about 40%, suggesting that the mullite-added catalysts have excellent hydrothermal stability, a finding that is consistent with previous work. 23,24 Besides, the T 30 for the oxidation of NO was 25 °C lower for the Bi 3+ -doped catalysts compared to the Bi 3+ -free catalysts. Further, based on the DOCs activities of catalysts doped with different bismuth contents shown in Figure S3, the optimal Bi doping was screened.…”

Construction of a Highly Active Rh/CeO₂-ZrO₂-Al₂O₃ Catalyst Based on Rh Micro-Chemical State Regulation and Its Three-Way Catalytic Activity

“…The catalysts were characterized by XRD, H2-TPR, pulse CO chemisorption, CO-FTIR, TEM, XPS and in situ DRIFTS according to the procedure described in our previous work 19,20,23 .…”

Revealing the Tunable Effects of Single Metal Atoms Supported on Nitrogen-Doped Carbon Nanotubes during NO Oxidation from Microkinetic Simulation

“…Recently, single atom catalysts (SACs) have attracted extensive attention with good selectivity and durability. , In particularly, in principle, SACs could reach a 100% atom efficiency and significantly reduce the noble metal usage. Recent studies indicated that SACs demonstrated impressive potential and capability in electrocatalysis, , photocatalysis, − and thermocatalysis − reactions. The appealing features of SACs could potentially break the bottleneck of current NO oxidation catalysts.…”