Insights into the promotional effect of alkaline earth metals in Pt-based three-way catalysts for NO reduction

Fan, Jun; Chen, Liuling; Li, Shanshan; Mou, Jialin; Lu, Zixing; Jiao, Yi; Wang, Jianli; Chen, Yaoqiang

doi:10.1016/j.jcat.2023.01.009

Cited by 15 publications

(3 citation statements)

References 60 publications

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“…According to the experimental procedures of our laboratory 22 , the monolithic honeycomb catalysts were prepared by applying a slurry to a monolithic honeycomb. The slurry consisted of calcined catalyst powders, deionized water and inorganic binder.…”

Section: Experimental Section 21 Catalysts Preparationmentioning

confidence: 99%

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

Mou¹,

Chen²,

Fan³

et al. 2023

Acta Physico Chimica Sinica

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With the increasing number of automobile vehicles, the exhaust emitted poses a severe menace to the environment and human health, necessitating the purification of exhaust pollutants. Meanwhile, the high price of noble metals and their limited supply require a decrease in noble metal loading to reduce the costs of three-way catalysts (TWCs). Therefore, improving the utilization efficiency of noble metals and their catalytic behavior is critical for the development of next-generation TWCs with low noble metal loading. Herein, the Rh micro-chemical state was modulated using the liquid-phase reduction method combined with atmospheric heat treatment to enhance the catalytic behavior of Rh-based catalysts with low Rh loading. The catalyst was characterized using X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), CO chemisorption, X-ray photoelectron spectroscopy (XPS), the FTIR spectroscopy of chemisorbed CO (CO-FTIR), transmission electron microscopy (TEM), and in situ diffuse reflectance IR (in-situ DRIFTS) to illustrate the relationship between Rh micro-chemical state (including valence state ratio and dispersion) and catalytic activity. The asprepared catalyst re-Rh/CeO2-ZrO2-Al2O3-H2 (re-Rh/CZA-H2) exhibited better catalytic activity and a wider air/fuel ratio (λ) operating window with T90 values 30-73 °C and 51-86 °C lower than those of the catalysts synthesized by liquid-phase reduction and traditional impregnation method, respectively. In addition, aged samples prepared by the combined scheme also exhibited excellent activity and stability, where the T50 and T90 values were lower than the fresh catalyst. Structureactivity relationship results demonstrated that the better catalytic activity of re-Rh/CZA-H2 could be attributed to the optimal valence state ratio and highly dispersed Rh species, which increased the number of effective active sites. The considerable stability was attributed to the stable structure of the CeO2-ZrO2-Al2O3 (CZA) support, improved dispersion, and the high contents of active Rh species, which exposed more active sites to promote reactant conversion. In addition, the synergistic effect between the metallic Rh and oxygen vacancies could facilitate the anchoring of Rh nanoparticles to inhibit Rh sintering. Therefore, adjusting the micro-chemical state of noble metals by the combinatorial scheme developed herein provides a novel route for improving the catalytic activity, high-temperature stability, and air/fuel operating window of these catalysts.

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Section: Experimental Section 21 Catalysts Preparationmentioning

confidence: 99%

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

Mou¹,

Chen²,

Fan³

et al. 2023

Acta Physico Chimica Sinica

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“…In recent years, precious metal catalysts loaded on activated carbon or “reducible” carriers have been very effective redox catalysts due to their high activity and excellent low-temperature catalytic properties. In previous reports, three-phase catalysts with platinum group metals (PGMs) dispersed as nanoparticles on oxide carriers have been reported to have good application [ 4 ]. Nanoscale particle size is used instead of the micron scale because nanoscale leads to an increase in specific surface area, which can lead to large surface energy and an increase in contact area at the reaction interface [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

Migration: A Neglected Potential Contribution of HCl-Oxidized Au(0)

Zhang

Wang

et al. 2023

Molecules

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In this study, the typical oxidation process of Au/C catalysts exposed to HCl is presented. Although the process violates the standard electrode potentials, the “oxidized” tendency of Au(0) species is analyzed. This oxidation behavior can only be triggered over the Au/C sample within residual cationic Au species, and terminated over the completely metallic Au(0)/C sample. This study demonstrates that the presence of surface chlorination species cannot facilitate the oxidation of Au(0) and Au(I) when the sample is treated with HCl alone, which excludes the oxidation paths of: Au(0) → Au(III) and Au(I) → Au(III). The reported “HCl-oxidized Au(0)” behavior is partially caused by the migration of Au(III) species in the carbon bulk-phase, which occurs outside the XPS detection limit region and into the detection limit rather than the “HCl-oxidized Au(0)” itself. The mechanism of driving the bulk-phase Au(III) migrated from the steady destabilized state to the carbon surface is then studied. This study demonstrates that the migration of Au cannot be neglected behind the curious oxidation phenomenon by HCl, which provides a new perspective for the oxidation of other noble metals by HCl.

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“…Due to the excellent catalytic performance of Pd-Rh-based TWC, contemporary commercial TWC used in natural gas vehicles generally comprises Pd and a relatively small amount of Rh [7,8]. However, the rising price of Pd and Rh in recent years has hindered the application of Pd-Rh TWC [9]. In the past five years, the price of Pt has been lower and more stable than that of Pd and Rh [10,11].…”

Section: Introductionmentioning

confidence: 99%

Steam Treatment Promotion on the Performance of Pt/CeO2 Three-Way Catalysts for Emission Control of Natural Gas-Fueled Vehicles

Liu,

Shao,

Ren

et al. 2023

Catalysts

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Three-way catalyst (TWC) is the mainstream technology for stoichiometric natural gas vehicle gas emission purification to meet the China VI emission standard for heavy-duty vehicles. Due to the high price of Pd-Rh TWC widely used at present, it is of great significance to develop cheaper Pt-only catalysts as substitutes. However, there are few studies on Pt-only TWC, especially for natural gas vehicles. It remains a formidable challenge to develop Pt-only TWC with excellent activity and stability. In this study, we significantly improved the catalytic performance of Pt/CeO2 TWC through thermal treatment, especially steam treatment at 800 °C, and used XRD, TEM, H2-TPR, and XPS techniques to investigate how Pt/CeO2 can be activated via these treatments. Our results suggested that after these treatments, CeO2 crystallites sintered slightly, while platinum particles remained highly dispersed. Moreover, these treatments also weakened the Pt-CeO2 interaction, promoted the formation of oxygen vacancies in CeO2 support, and generated a new type of active surface oxygen in the vicinity of Ptδ+, thus improving the activity of the catalyst. After 800 °C steam treatment, the T50 of CH4 and NO decreased by 31 and 36 °C, respectively. The results obtained in this study provide implications for the synthesis of efficient Pt-based catalysts.

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Insights into the promotional effect of alkaline earth metals in Pt-based three-way catalysts for NO reduction

Cited by 15 publications

References 60 publications

Construction of a Highly Active Rh/CeO<sub>2</sub>-ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Catalyst Based on Rh Micro-Chemical State Regulation and Its Three-Way Catalytic Activity

Construction of a Highly Active Rh/CeO<sub>2</sub>-ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Catalyst Based on Rh Micro-Chemical State Regulation and Its Three-Way Catalytic Activity

Migration: A Neglected Potential Contribution of HCl-Oxidized Au(0)

Steam Treatment Promotion on the Performance of Pt/CeO2 Three-Way Catalysts for Emission Control of Natural Gas-Fueled Vehicles

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