Redox behavior of palladium at start-up in the Perovskite-type LaFePdO  automotive catalysts showing a self-regenerative function

Uenishi, Mari; Taniguchi, Masateru; Tanaka, Hiroyuki; Kimura, M.; Nishihata, Yasuo; Мizuki, J.; Kobayashi, Tetsuhiko

doi:10.1016/j.apcatb.2004.11.011

Cited by 133 publications

(99 citation statements)

References 10 publications

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“…Therefore, palladium reversibly moves in and out of the perovskite matrix in response to the cyclic redox fluctuations of the exhaust gas composition. These reversible structural changes, which are fast (only a few seconds at 600 °C [14]) and occur even at low temperature (100-400 °C) [72,73], suppress the growth of Pd particles compared to Pd/Al 2 O 3 . To illustrate this phenomenon, the behaviors of two catalysts of similar initial activity are compared after ageing in a real exhaust at 900 °C for 100 h. The reference Pd/γ-Al 2 O 3 catalyst loses about 10% of its activity ( Figure 6) owing to the sintering of noble metal particles (D > 100 nm).…”

Section: Incorporation Of a Noble Metalmentioning

confidence: 99%

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

et al. 2014

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Automotive Three-Way Catalysts (TWC) were introduced more than 40 years ago. Despite that, the development of a sustainable TWC still remains a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among other material classes, perovskite-type oxides are known to be valuable alternatives to conventionally used TWC compositions and have demonstrated to be suitable for a wide range of automotive applications, ranging from TWC to Diesel Oxidation Catalysts (DOC), from NO x Storage Reduction catalysts (NSR) to soot combustion catalysts. The interest in these catalysts has been revitalized in the past ten years by the introduction of the concept of catalyst regenerability of perovskite-based TWC, which is in principle well applicable to other catalytic processes as well, and by the possibility to reduce the amounts of critical elements, such as precious metals without seriously lowering the catalytic performance. The aim of this review is to show that perovskite-type oxides have the potential to fulfil the requirements (high activity, stability, and possibility to be included into structured catalysts) for implementation in TWC.

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Section: Incorporation Of a Noble Metalmentioning

confidence: 99%

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

et al. 2014

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“…[24][25][26] Since the reactive nano-catalyst particles are formed at the reaction surfaces, we can expect very fast start-up for the catalytic activity. If the host matrix is enough stable, we can hope high endurance against the heat, since the reacting nano-catalysts keep their size in nano-scale.…”

Section: /10mentioning

confidence: 99%

Generation of Nano-Catalyst Particles by Spinodal Nano-Decomposition in Perovskite

Kizaki

Kusakabe

Nogami

et al. 2008

Appl. Phys. Express

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A new mechanism of nano-catalyst generation based on the spinodal nano-decomposition in self-regenerating perovskite catalysts for automotive-emissions control is proposed. To demonstrate existence of the spinodal nano-decomposition in real perovskite catalysts, we performed first-principles calculations to evaluate the free energy of La(Fe 1−x Pd x )O 3 and La(Fe 1−x Rh x )O 3 . The result indicates appearance of a spinodal region in the phase diagram of each material. Formation of nano-catalyst particles in the perovskite host matrix is crucial for the self-regeneration of perovskite catalyst. Based on the spinodal nano-decomposition model, possible materials are designed for new three-way catalyst with no contents of precious metal.Self-regenerating Pd-, Rh-, and Pt-doped perovskite catalysts for automotive-emissions control are attracting much interest due to their unique functionalities. [1][2][3][4][5][6][7][8][9][10][11] In a conventional catalyst made of fine precious-metal particles supported on a solid like an almina, agglomeration of the metal particles is inevitable because of high temperature conditions in the redox environment. This is the very reason for deterioration of automotive three-way catalysts. In the self-regenerating perovskite catalysts, interestingly, the deterioration is strongly suppressed. Therefore, consumption of the precious metal is greatly reduced, providing a highly efficient solution for supply problems. The reason for non-deterioration is thought to be reformation of a precious-metal doped perovskite lattice in the NO x -reduction environment from segregated nano-particles of precious-metal created in the CO-and C x H-oxidation environment. In this regeneration model, precious-metal atoms are assumed to move into and out of the perovskite host matrixes. Growth of precious-metal grains is suppressed due to this repeated motion of precious metal atoms between a solid solution and metallic nano-particles during three-way catalytic reactions.In some doped perovskite structures, it is known that diffusion of oxygen happens rather frequently. At the same time, we may expect motion of metal atoms via a process exchanging metallic atoms. The process would be enhanced, if oxygen vacancies are created in the perovskite host crystal. This scenario might support the above model of self-regenerating perovskite catalysts. For realization of high efficiency in the three-way catalytic functions with * E-mail address: hkizaki@aquarius.mp.es.osaka-u.ac.jp 1/10Submitted to Applied Physics Express no deterioration, however, we should consider another model of the self-regenerating catalyst. The new model should explain some mysteries known experimentally in the perovskite catalyst. The self-regeneration can happen, only when the host perovskite lattice structure maintains its essential structure. We need to know why the redox reaction keeps its cycle in a redox environment changing in a frequency of about a few hertz (1 ∼ 4 Hz). Thus we need to understand motion of precious metal atoms in a rat...

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“…Based on the narrow width (FWHM = 1.92 eV) and the symmetry of the Pd 3d 5/2 peak, the Pd species were defined as Pd n? (2 \ n \ 4), located at the B-sites [9,16]. In contrast, the binding energy of Pd 3d 5/2 (336.8 eV) in the reference Pd/ LaFeO 3 sample was characteristic of PdO.…”

Section: Co Oxidationmentioning

confidence: 89%

“…The peak at 400 K was attributed to reduction of Pd n? species within the perovskite to metallic Pd [16]. The weak peak at 529 K represented the reduction of a small amount of Fe 4?…”

Section: Co Oxidationmentioning

confidence: 99%

Dynamic Behavior of Pd Species in an LaFe0.95Pd0.05O3 Perovskite

Zhang

et al. 2011

Catal Lett

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Redox behavior of palladium at start-up in the Perovskite-type LaFePdO automotive catalysts showing a self-regenerative function

Cited by 133 publications

References 10 publications

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

Generation of Nano-Catalyst Particles by Spinodal Nano-Decomposition in Perovskite

Dynamic Behavior of Pd Species in an LaFe0.95Pd0.05O3 Perovskite

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