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Surface formation markedly influences the stability and properties of nanoalloys. The surface states of nanoalloys are sensitive to the constituent elements and to the surrounding environment. In this study, Fourier transform-infrared (FT-IR) spectroscopy and an evolution strategy (ES) combined with density functional theory calculations and multivariate analysis were used to explore the stable configuration of NO-adsorbed PdRu nanoalloys. FT-IR analysis indicated that the NO molecules were adsorbed on the Ru-related sites, which was inconsistent with the stable surface state of the isolated PdRu nanoalloy models. The ES revealed that the stable surface state consisted mainly of Ru atoms owing to molecular adsorption. In addition, the Pd–Ru mixing was facilitated by the adsorption. According to the multivariate analysis, the adsorption energies on the Ru-related sites were more negative than those on the Pd-related sites and became more negative as the number of neighboring Pd atoms increased. These adsorption characteristics are opposite to those of the stability of the isolated PdRu nanoalloys. The energy gain owing to NO adsorption overcomes the energy loss due to the Pd–Ru bonds and placement of Ru atoms at the surface. This study highlights the importance of understanding stable surface states in a reactive atmosphere for the application of nanoalloys.

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 LaFe0.95Pd0.05O3-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. Despite such selective dissolution during oxidation, all three elements remain cooperatively alloyed in the subsequent reduction, which is a key factor in preserving the catalytic activity of the ternary nanoalloy while displaying its self-regenerating functionality and control of particle agglomeration.

The crystal structure of Co-based perovskite oxides (ACoO3) can be controlled by adjusting the A-site elements. In this study, we synthesized Y1–xBaxCoO3−δ(x= 0, 0.5, and 1.0) via a coprecipitation method and investigated their CO oxidation performances. YCoO3(x= 0; cubic perovskite oxide; Pbnm) shows a higher catalytic performance than Y0.5Ba0.5CoO2.72(x= 0.5; A-site-ordered double perovskite oxide; P4/nmm), which exhibits high oxygen nonstoichiometric properties, and BaCoO3(x= 1.0; hexagonal perovskite oxide; P63/mmc), which contains high-valent Co4+species. To elucidate the reaction mechanism, we conducted isotopic experiments with CO and 18O2. The CO oxidation reaction on YCoO3proceeds via the Langmuir–Hinshelwood mechanism, which is a surface reaction of CO and O2gas that does not utilize lattice oxygen. Because of the significantly smaller specific surface area of YCoO3compared with that of the reference Pt/Al2O3, the bulk features of the crystal structures affect the catalytic reaction. When density functional theory is applied, YCoO3clearly exhibits semiconducting properties in the ground state with the diamagnetic t2g6eg0states, which can translate to a magnetic t2g5eg1configuration upon excitation by a relatively low energy of 0.64 eV. We propose that the unique nature of YCoO3activates oxygen in the gas phase, thereby enabling the smooth oxidation of CO. This study demonstrates that the bulk properties originating from the crystal structure contribute to the catalytic activity and reaction mechanism.

In this study, homogeneously distributed PdxPt1–xdual-atom-site catalysts (DASC) were successfully synthesized over the whole composition range. In the three-way catalytic performance tests, Pd0.5Pt0.5and Pd0.9Pt0.1DASC exhibited greatly enhanced C3H6oxidation activities over those of pure Pd and Pt nanoparticles. During in situFourier transform infrared measurements, the direct C3H6dissociations on Pd–Pt dual-atom sites were discovered, which were mainly responsible for the superior C3H6oxidation activities of Pd0.5Pt0.5and Pd0.9Pt0.1DASC. In addition, a linear correlation between activity curves and Pt–CO wavenumbers was found, indicating that the IR wavenumber is a descriptor for activation energy.

K/Co4MnAlOxmixed oxides are active in direct NO decomposition. This work investigates the effect of the preparation method and K precursor type. Using the incipient wetness impregnation method, the modification by the required amount of K was ensured. Regardless of the K precursor type, similar NO conversions were reached for samples modified by 4 wt % K. The optimal amount of K from the KNO3precursor was evaluated as 2–6 wt %. The physicochemical properties were carefully explored using atomic absorption spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform IR spectroscopy, N2physisorption, H2temperature-programmed reduction, CO2and NO temperature-programmed desorption, scanning electron microscopy, and transmission electron microscopy, correlated with catalytic properties in transient and steady state and compared with the results obtained in our previous study using bulk modified samples. The present study underlines the effect of the preparation method on the Brunauer–Emmett–Teller surface area (SBET) of prepared catalysts and thus the amount of active sites available for catalytic reaction. Moreover, the results emphasize the importance of catalyst basicity, which affects the amount of adsorbed NO2–species, the key intermediates in the direct NO catalytic reaction.