Atomic-Scale Behavior of Perovskite-Supported Ir-Pd-Ru Nanoparticles under Redox Atmospheres.

An advanced materials solution utilizing the concept of "smart catalysts" could be a game changer for today's automotive emission control technology, enabling the efficient use of precious metals via their two-way switching between metallic nanoparticle forms and ionic states in the host perovskite lattice as a result of the cyclical oxidizing/reducing atmospheres. However, direct evidence for such processes remains scarce; therefore, the underlying mechanism has been an unsettled debate. Here, we use advanced scanning transmission electron microscopy to reveal the atomic-scale behaviors for a LaFePdO-supported Ir-Pd-Ru nanocatalyst under fluctuating redox conditions, thereby proving the reversible dissolution/exsolution for Ir and Ru but with a limited occurrence for Pd.

Experimental and Computational Insights into the Catalytic Mechanism of YBaCoO Perovskite Oxides with a Controlled Crystal Structure.

The crystal structure of Co-based perovskite oxides (ACoO) can be controlled by adjusting the A-site elements. In this study, we synthesized YBaCoO ( = 0, 0.5, and 1.

Room Temperature Reduction of Nitrogen Oxide on Iron Metal-Organic Frameworks.

Nitrogen oxides represent one of the main threats for the environment. Despite decades of intensive research efforts, a sustainable solution for NO removal under environmental conditions is still undefined. Using theoretical modelling, material design, state-of-the-art investigation methods and mimicking enzymes, it is found that selected porous hybrid iron(II/III) based MOF material are able to decompose NO, at room temperature, in the presence of water and oxygen, into N and O and without reducing agents.

Denary High-Entropy Oxide Nanoparticles Synthesized by a Continuous Supercritical Hydrothermal Flow Process.

High-entropy oxide nanoparticles (HEO NPs) have been intensively studied because of their attractive properties, such as high stability and enhanced catalytic activity. In this work, for the first time, denary HEO NPs were successfully synthesized using a continuous supercritical hydrothermal flow process without calcination. Interestingly, this process allows the formation of HEO NPs on the order of seconds at a relatively lower temperature.

Reactivity of Lattice Oxygen in Ti-Site-Substituted SrTiO Perovskite Catalysts.

An environmental catalyst in which a transition metal (Mn, Fe, or Co) was substituted into the Ti site of the host material, SrTiO, was synthesized, and the reactivity of lattice oxygen was evaluated. For CO oxidation, Mn- and Co-doped SrTiO catalysts, which provided high thermal stabilities, exhibited higher activities than Pt/AlO catalysts despite their low surface areas. Temperature-programmed reduction experiments using X-ray absorption fine structure (XAFS) measurements showed that the lattice oxygen of Co-doped catalyst was released at the lowest temperature.

Slow Synthesis Methodology-Directed Immiscible Octahedral Pd Rh Dual-Atom-Site Catalysts for Superior Three-Way Catalytic Activities over Rh.

This study provided an effective strategy to construct dual-atom sites by solid-solution alloying. A slow synthesis methodology was established for the solid-solution preparations as dual-atom-site catalysts. The atomic-level homogeneous Pd Rh dual-atom-site catalysts were successfully synthesized over the whole composition range, as evidenced by X-ray powder diffraction and scanning transmission electron microscope energy-dispersive X-ray spectroscopy mapping measurements.

Spiky-shaped niobium pentoxide nano-architecture: highly stable and recoverable Lewis acid catalyst.

Niobium pentoxide particles with a complex three-dimensional (3D) nanostructure consisting of a spiky structure have been developed as recyclable and recoverable Lewis acid catalysts. The morphology of the niobium pentoxide was successfully controlled from 1D to 3D via a bridging-ligand-assisted hydrothermal treatment, without changing the crystal structure. Compared with dispersed one-dimensional (1D) niobium pentoxide nanorods with a major-axis length and minor-axis length of 20 nm and 5-8 nm, respectively, the spiky-shaped niobium pentoxide composed of 300 nm spherical cores and nanorods with a minor-axis length of 5 nm maintained its surface nanostructure even after calcination at 400 °C in air.

Significantly enhanced CO oxidation activity induced by a change in the CO adsorption site on Pd nanoparticles covered with metal-organic frameworks.

We report the significantly enhanced CO oxidation activity of Pd nanoparticles covered with [ZrO(OH)(BDC)] (UiO-66, BDC = 1,4-benzenedicarboxylate). The catalytic activity was much higher than those of Pd and Ru nanoparticles on ZrO. The origin of the enhancement was suggested to be a change in the CO adsorption properties on Pd nanoparticles.

Promoting Effect of Cerium Oxide on the Catalytic Performance of Yttrium Oxide for Oxidative Coupling of Methane.

The promoting effect of CeO on the catalytic performance of YO, which is moderately active catalyst, for the oxidative coupling of methane (OCM) reaction was investigated. The addition of CeO into YO by coprecipitation method caused a significant increase in not only CH conversion but also C (CH/CH) selectivity in the OCM reaction. C yield at 750 °C was increased from 5.

A CO Adsorption Site Change Induced by Copper Substitution in a Ruthenium Catalyst for Enhanced CO Oxidation Activity.

Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru.

Complex Three-Dimensional Co₃O₄ Nano-Raspberry: Highly Stable and Active Low-temperature CO Oxidation Catalyst.

Highly stable and active low-temperature CO oxidation catalysts without noble metals are desirable to achieve a sustainable society. While zero-dimensional to three-dimensional Co₃O₄ nanoparticles show high catalytic activity, simple-structured nanocrystals easily self-aggregate and become sintered during catalytic reaction. Thus, complex three-dimensional nanostructures with high stability are of considerable interest.

Adsorption and reactions of NO on clean and CO-precovered Ir(111).

Adsorption and reactions of NO on clean and CO-precovered Ir(111) were investigated by means of X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HR-EELS), infrared reflection absorption spectroscopy (IRAS), and temperature-programmed desorption (TPD). Two NO adsorption states, indicative of fcc-hollow sites and atop sites, were present on the Ir(111) surface at saturation coverage. NO adsorbed on hollow sites dissociated to Na and Oa at temperatures above 283 K.

Ir/SiO2 as a highly active catalyst for the selective reduction of NO with CO in the presence of O2 and SO2.

Coexisting SO2 considerably enhanced the catalytic activity of Ir/SiO2 for NO reduction with CO in the presence of O2 because of the formation of a cis-type coordinated species of NO and CO to one iridium atom ([formula: see text]), a possible reaction intermediate leading to N2 formation.

Comprehensive study combining surface science and real catalyst for NO direct decomposition.

The catalytic activity of Pd/Al2O3 prepared from various palladium precursors for direct NO decomposition is closely related to the fraction of surface step sites capable of dissociating NO, on the basis of a surface science study using single-crystal model catalyst.