Enhanced Catalytic Efficiency of Pt Nanoparticles Supported on 3D Ordered Macro-/Mesoporous Ce0.6 Zr0.3 Y0.1 O2 for Methane Combustion

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Surface redox characters and synergetic catalytic properties of macroporous ceria-zirconia solid solutions

Macroporous CeO₂-ZrO₂ (CZ) solid solutions with gradually changing ceria content were prepared through the EISA method. Pore sizes of the samples are about 100 nm-1 μm and pore walls are 100 nm-1.5 μm. The surface and near surface reduction bands of Ce⁴⁺ below 600 °C were maximized for the Ce_0.5Zr_0.5O₂ sample (C5) according to the quantitative de-convolution to the acquired TPR curves. The area percentage of the O^2-2p⁶ → Ce³⁺3d⁹4f² electronic transition band on XPS spectra, which related to the concentration of the Ce³⁺, was found to be a function of the ceria content. The oxygen storage capacity showed a positive relationship with the chemical compositions. Redox reactions below 600 °C play a key role in determining the reduction performances of ceria based TWCs. Three-way catalytic performances of the Pd + Rh + Pt /C5 sample showed an ignition temperature for CO and NOx at about 240 °C, and finished before 300 °C. The ignition of C₃H₈ started at 270 °C while finished at differed samples. The maximum catalytic efficiencies of CO, NOx, and C₃H₈ on C5 sample were revealed to 100%, 98%, and 97%, respectively. The performances showed that porous CZ solid solutions are suitable for high performance catalytic applications.

A perovskite oxide with a tunable pore-size derived from a general salt-template strategy as a highly efficient electrocatalyst for the oxygen evolution reaction

A porous perovskite oxide is fabricated by an inorganic salt-template strategy, which exhibits remarkable performance for the oxygen evolution reaction.

Ordered meso- and macroporous perovskite oxide catalysts for emerging applications

Hierarchically ordered perovskite materials which have potential applications in chemistry, energy and materials science.

Effects of A-site non-stoichiometry in YxInO3+δ on the catalytic performance during methane combustion

A novel non-stoichiometric Y_xInO_3+δ (YIO-x, 0.8 ≤ x ≤ 1.04) perovskite catalyst with a large number of oxygen vacancies and high specific surface area was synthesized using glycine self-propagating gel combustion. It was found that low levels of non-stoichiometry in the A site of Y_xInO_3+δ effectively increased the amount of oxygen desorption by 39-42% when compared to the original (YIO-1) due to Y-deficiency and oxygen vacancies. Further investigations showed that the non-stoichiometry also brings a significant change to the Lewis acid sites on the surface of the sample, which confirmed to be a great promoter for the catalytic combustion of methane. In addition, the catalytic performance increased with the increasing intensity of acid sites. After 50 h of the stability test, the catalysts maintained high activity, indicating their good catalytic stability.

Self-Assembled Pd@CeO2 /γ-Al2 O3 Catalysts with Enhanced Activity for Catalytic Methane Combustion

Pd@CeO₂ /Al₂ O₃ catalysts are of great importance for real applications, such as three-way catalysis, CO oxidation, and methane combustion. In this article, the Pd@CeO₂ core@shell nanospheres are prepared via the autoredox reaction in aqueous phase. Three kinds of methods are then employed, that is, electrostatic interaction, supramolecular self-assembly, and physical mixing, to support the as-prepared Pd@CeO₂ nanospheres on γ-Al₂ O₃ . A model reaction of catalytic methane-combustion is employed here to evaluate the three Pd@CeO₂ /γ-Al₂ O₃ samples. As a result, the sample Pd@CeO₂ -S-850 prepared via supramolecular self-assembly and calcined at 850 °C exhibits superior catalytic performance to the others, which has a far lower light-off temperature (T₅₀ of about 364 °C). Moreover, almost no deterioration of Pd@CeO₂ -S-850 is observed after five sequent catalytic cycles. The analysis of H₂ -TPR curves concludes that there exists hydrogen spillover related to the strong metal-support interaction between Pd species and oxides. The strong metal-support interaction and the specific surface areas might be responsible for the catalytic performance of the Pd@CeO₂ samples toward catalytic methane combustion.

Simultaneous removal of PM and NOx over highly efficient 3DOM W/Ce0.8Zr0.2O2 catalysts

Herein, three-dimensional ordered macropore (3DOM) x% W/Ce_0.8Zr_0.2O₂ (x = 0.5, 0.8, 1, 3) catalysts were prepared and employed for the simultaneous removal of PM (particulate matter) and NO_x from diesel engine exhaust.

Meso-Molding Three-Dimensional Macroporous Perovskites: A New Approach to Generate High-Performance Nanohybrid Catalysts

Newly designed 3D highly ordered macro/mesoporous multifunctional La1-xCexCoO3 nanohybrid frameworks with a 2D hexagonal mesostructure were fabricated via facile meso-molding in a three-dimensionally macroporous perovskite (MTMP) route. The nanohybrid framework exhibited excellent catalytic activity for methane combustion, which derived from the MTMP providing a larger surface area and pore volume, uniform pore sizes, higher accessible surface oxygen concentration, better low-temperature reducibility, and a unique nanovoid 3D structure.