A sacrificial coating strategy toward enhancement of metal-support interaction for ultrastable Au nanocatalysts

Supported gold (Au) nanocatalysts hold great promise for heterogeneous catalysis; however, their practical application is greatly hampered by poor thermodynamic stability. Herein, a general synthetic strategy is reported where discrete metal nanoparticles are made resistant to sintering, preserving their catalytic activities in high-temperature oxidation processes. Taking advantage of the unique coating chemistry of dopamine, sacrificial carbon layers are constructed on the material surface, stabilizing the supported catalyst. Upon annealing at high temperature under an inert atmosphere, the interactions between support and metal nanoparticle are dramatically enhanced, while the sacrificial carbon layers can be subsequently removed through oxidative calcination in air. Owing to the improved metal–support contact and strengthened electronic interactions, the resulting Au nanocatalysts are resistant to sintering and exhibit excellent durability for catalytic combustion of propylene at elevated temperatures. Moreover, the facile synthetic strategy can be extended to the stabilization of other supported catalysts on a broad range of supports, providing a general approach to enhancing the thermal stability and sintering resistance of supported nanocatalysts

Efficient current-induced spin torques and field-free magnetization switching in a room-temperature van der Waals magnet

The discovery of magnetism in van der Waals (vdW) materials has established unique building blocks for the research of emergent spintronic phenomena. In particular, owing to their intrinsically clean surface without dangling bonds, the vdW magnets hold the potential to construct a superior interface that allows for efficient electrical manipulation of magnetism. Despite several attempts in this direction, it usually requires a cryogenic condition and the assistance of external magnetic fields, which is detrimental to the real application. Here, we fabricate heterostructures based on Fe3GaTe2 flakes that possess room-temperature ferromagnetism with excellent perpendicular magnetic anisotropy. The current-driven non-reciprocal modulation of coercive fields reveals a high spin-torque efficiency in the Fe3GaTe2/Pt heterostructures, which further leads to a full magnetization switching by current. Moreover, we demonstrate the field-free magnetization switching resulting from out-of-plane polarized spin currents by asymmetric geometry design. Our work could expedite the development of efficient vdW spintronic logic, memory and neuromorphic computing devices

Highly efficient and stable Ru/K-OMS-2 catalyst for NO oxidation

The influence of addition of a series of non noble and noble metals to a manganese oxide octahedral molecular sieve (OMS) with a cryptomelane structure (K-OMS-2) has been studied for NO oxidation in view of fast selective catalytic reduction applications. Fe, Cu, Zn, Pt, Pd, Ru and Ag were selected as dopant metals with a metal loading around 2 wt.%. The catalysts were characterized in detail by ICP-OES, N2 adsorption/desorption at 77 K, XRD, H2-TPR and HR-TEM. The highest NO conversion was obtained for a K-OMS-2 catalyst modified with ruthenium, showing a reaction rate up to 5.3 μmol g−1 s−1 at 584 K. A markedly higher catalyst reducibility upon incorporation of ruthenium can be proposed as an underlying reason for the enhanced catalytic performance.Se ha estudiado la influencia de la adición de una serie de metales nobles y no nobles a un tamiz molecular octaédrico (OMS) de óxido de manganeso con estructura de criptomelano (K-OMS-2) para la oxidación de NO con vistas a aplicaciones de reducción catalítica selectiva rápida. Se seleccionaron Fe, Cu, Zn, Pt, Pd, Ru y Ag como metales dopantes con una carga de metal de alrededor del 2 % en peso. Los catalizadores se caracterizaron en detalle por ICP-OES, adsorción/desorción de N 2 a 77 K, XRD, H 2 -TPR y HR-TEM. La mayor conversión de NO se obtuvo para un catalizador K-OMS-2 modificado con rutenio , mostrando una velocidad de reacción de hasta 5,3 μmol g - 1 s - 1 a 584 K. Se puede proponer una reducibilidad del catalizador marcadamente más alta tras la incorporación de rutenio como una razón subyacente para el rendimiento catalítico mejorado

Ball Milling-Assisted Synthesis of Ultrasmall Ruthenium Phosphide for Efficient Hydrogen Evolution Reaction

The development of scalable hydrogen production technology to produce hydrogen economically and in an environmentally friendly way is particularly important. The hydrogen evolution reaction (HER) is a clean, renewable, and potentially cost-effective pathway to produce hydrogen, but it requires the use of a favorable electrocatalyst which can generate hydrogen with minimal overpotential for practical applications. Up to now, ruthenium phosphide Ru2P has been considered as a high-performance electrocatalyst for the HER. However, a tedious post-treatment method as well as large consumption of solvents in conventional solution-based synthesis still limits the scalable production of Ru2P electrocatalysts in practical applications. In this study, we report a facile and cost-effective strategy to controllably synthesize uniform ultrasmall Ru2P nanoparticles embedded in carbon for highly efficient HER. The key to our success lies in the use of a solid-state ball milling-assisted technique, which overcomes the drawbacks of the complicated post-treatment procedure and large solvent consumption compared with solution-based synthesis. The obtained electrocatalyst exhibits excellent Pt-like HER performance with a small overpotential of 36 mV at current density of 10 mA cm−2 in 1 M KOH, providing new opportunities for the fabrication of highly efficient HER electrocatalysts in real-world applications

Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane

Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4), was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultravioletâvisible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(II)î¸N bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0%) of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated. Keywords: Selective oxidation of cyclohexane, Oxygen oxidant, Carbon nitride, Co-dopin

Catalytic Performance of MgO-Supported Co Catalyst for the Liquid Phase Oxidation of Cyclohexane with Molecular Oxygen

A highly-efficient and stable MgO-supported Co (Co/MgO) catalyst was developed for the oxidation of cyclohexane with oxygen. The effects of the Co loading and support on the catalytic activity of the supported Co3O4 catalyst were investigated. The results show that the Co supported on MgO presented excellent activity and stability. When the Co/MgO catalyst with the Co content of 0.2 wt% (0.2%Co/MgO) was used, 12.5% cyclohexane conversion and 74.7% selectivity to cyclohexanone and cyclohexanol (KA oil) were achieved under the reaction conditions of 0.5 MPa O2 and 140 °C for 4 h. After being repeatedly used 10 times, its catalytic activity was hardly changed. Further research showed that the high catalytic performance of the 0.2%Co/MgO catalyst is attributed to its high oxygen-absorbing ability and the high ratio between the amount of weak and medium base sites with the help of the synergistic interaction between Co and MgO

Insights into the Morphological Effect of Co₃O₄ Crystallite on Catalytic Oxidation of Vinyl Chloride

Co3O4 catalysts of cube and sphere shapes were prepared by one-step hydrothermal synthesis with different controlled amounts of Co(NO3)2·6H2O and NaOH. The morphological effects on both physicochemical properties and catalytic activities of vinyl chloride oxidation were investigated by material characterization and performance evaluation. The obtained results showed that the morphology, resulting in the exposure difference of crystal planes, significantly affected the catalytic property. The catalytic activity for vinyl chloride oxidation followed a descending order of Co3O4 cube (Co3O4-c) > Co3O4 sphere (Co3O4-s) > Co3O4 commercial (Co3O4-com). The cube-shaped Co3O4 presented higher catalytic activity and stability than Co3O4 spheres despite their similar crystallographic structures as well as physicochemical and redox properties. Accordingly, the different catalytic behaviors should be attributed to a morphological effect. The Co3O4 cube with a preferential exposure of (001) plane presented higher abundance of surface Co2+ cations and adsorbed oxygen species, which acted as the active sites responsible for the improvement of its catalytic activity