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Selective hydrogenation of substituted nitroaromatic compounds is an extremely important and challenging reaction. Supported metal catalysts attract much attention in this reaction because the properties of metal nanoparticles (NPs) can be modified by the nature of the support. Herein, the support morphology on the catalytic performance of selective hydrogenation of 3‐nitrostyrene to 3‐vinylaniline was investigated. Pt NPs supported on octadecahedral α‐Fe2O3 supports with a truncated hexagonal bipyramid shape (Pt/α‐Fe2O3‐O) and rod‐shaped α‐Fe2O3 supports (Pt/α‐Fe2O3‐R) were prepared by glycol reduction method. Detailed characterizations reveal that the electronic structure and dispersion of Pt NPs can be modified by the supports. The Pt/α‐Fe2O3‐O catalyst exhibited superior catalytic performance for hydrogenation of 3‐nitrostyrene because of its low coordinated Pt sites and the small Pt NPs size, which is benefit from the high‐index exposed surfaces of truncated hexagonal bipyramid‐shaped α‐Fe2O3 support. The structural evolution during the catalytic reaction was investigated in detail by identical location transmission electron microscopy (IL‐TEM) method, which found that the high cycling activity of Pt/α‐Fe2O3‐O catalyst during the cycle experiment results from the stability of Pt NPs. [ABSTRACT FROM AUTHOR]

Metallic platinum nanocatalysts play a key role in the liquid‐phase selective hydrogenation of substrates with more than one unsaturated bond. However, the commonly applied explanation for the effects of different electronic and geometric properties of catalysts on reactions remains of a heuristic nature due to the difficulties involved in preparing catalysts with precise structure. In this work, we have directly loaded pre‐synthesized metallic platinum nanoparticles onto well‐structured ZnO nanorods and then subjected them to thermal treatment in a reductive atmosphere for different temperatures. The effects of the different electronic and geometric properties of the catalysts on the selective reduction of 3‐nitrostyrene to 3‐vinylaniline as a model reaction have been rigorously explored through an analysis of the catalyst structures and the activity and selectivity profiles. Both the electron transfer from zinc to platinum and the decreased platinum surface density as a result of the formation of PtZn intermetallic compounds are key factors for improving the selectivity for the desired 3‐vinylaniline. Azobenzene was detected in the reaction with all the Pt/ZnO catalysts after 10–90 min, which indicates that the reaction follows a condensation mechanism. [ABSTRACT FROM AUTHOR]

Supported gold catalysts play a crucial role in the chemical industry; however, their poor on-stream stability because of the sintering of the gold nanoparticles restricts their practical application. The strong metal-support interaction (SMSI), an important concept in heterogeneous catalysis, may be applied to construct the structure of catalysts and, hence, improve their reactivity and stability. Here we report an ultrastable Au nanocatalyst after calcination at 800 °C, in which Au nanoparticles are encapsulated by a permeable TiOx thin layer induced by melamine under oxidative atmosphere. Owning to the formed TiOx overlayer, the resulting Au catalyst is resistant to sintering and exhibits excellent activity and stability for catalytic CO oxidation. Furthermore, this special strategy can be extended to colloidal Au nanoparticles supported on TiO2 and commercial gold catalyst denoted as RR2Ti, providing a universal way to engineer and develop highly stable supported Au catalysts with tunable activity. Sintering-resistant Au nanoparticles are highly desirable due to their low Tammann temperature. Here, the authors report an ultrastable titania-supported Au nanocatalyst through an encapsulation strategy under oxidative atmosphere. [ABSTRACT FROM AUTHOR]

Graphene oxides (GOs) are popular catalyst supports for precious metals in nanoparticle form. The hydrogen oxidation reaction (HOR) and the hydrogen evolution reaction (HER) on individual GO platelets decorated with Pd nanoparticles (Pd/GOs) were investigated. The results suggest that the catalytic activity is confined to the zone physically close to the point of electrical contact between platelet and electrode with just a fraction of the platelet active. [ABSTRACT FROM AUTHOR]

Controllable synthesis of well‐defined supported intermetallic catalysts is desirable because of their unique properties in physical chemistry. To accurately pinpoint the evolution of such materials at an atomic‐scale, especially clarification of the initial state under a particular chemical environment, will facilitate rational design and optimal synthesis of such catalysts. The dynamic formation of a ZnO‐supported PdZn catalyst is presented, whereby detailed analyses of in situ transmission electron microscopy, electron energy‐loss spectroscopy, and in situ X‐ray diffraction are combined to form a nanoscale understanding of PdZn phase transitions under realistic catalytic conditions. Remarkably, introduction of atoms (H and Zn in sequence) into the Pd matrix was initially observed. The resultant PdHx is an intermediate phase in the intermetallic formation process. The evolution of PdHx in the PdZn catalyst initializes at the PdHx/ZnO interfaces, and proceeds along the PdHx ⟨111⟩ direction. A palladium catalyst supported on ZnO is monitored in situ and in chemical environments relevant to catalysis. Structural evolution of PdZn intermetallic metal nanoparticles (NPs), visualized at an atomic scale, reveals the evolution of a PdHx intermediary species at the interface between PdHx and the ZnO support. [ABSTRACT FROM AUTHOR]

The preparation of photocatalysts with high activities under visible-light illumination is challenging. We report the rational design and construction of a zirconium-doped anatase catalyst (S-Zr-TiO2) with Brønsted acidity and photoactivity as an efficient catalyst for the degradation of phenol under visible light. Electron microscopy images demonstrate that the zirconium sites are uniformly distributed on the sub-10 nm anatase crystals. UV-visible spectrometry indicates that the S-Zr-TiO2 is a visible-light-responsive catalyst with narrower band gap than conventional anatase. Pyridine-adsorption infrared and acetone-adsorption 13C NMR spectra confirm the presence of Brønsted acidic sites on the S-Zr-TiO2 sample. Interestingly, the S-Zr-TiO2 catalyst exhibits high catalytic activity in the degradation of phenol under visible-light illumination, owing to a synergistic effect of the Brønsted acidity and photoactivity. Importantly, the S-Zr-TiO2 shows good recyclability. [ABSTRACT FROM AUTHOR]

A prototype supported solid-acid catalyst composed of a heteropoly acid (HPA) and nitrogen-functionalized carbon nanotubes (NCNT) has been developed. The chemical structure and acid strength of the HPA/NCNT hybrid have been characterized thoroughly by IR spectroscopy, X-ray photoelectron spectroscopy, TEM, and titration measurements. NCNT supports provide the HPA with an ideal hydrophobic environment, which could prevent the deactivation of the acid sites effectively in aqueous media. HPA/NCNT hybrid catalysts tend to adsorb and enrich hydrophobic substrates (ester) and release the product with high polarity (ethanol) in the aqueous phase, and this synergistic effect facilitates the catalytic process and enhances the activity of HPAs for ester hydrolysis reactions. The HPA and NCNT combine through electrostatic interactions, which ensures the relatively high stability and easy regeneration of the HPA/NCNT hybrid catalysts. The present approach provides a promising and universal strategy for the construction of hybrid catalysts based on HPA and nanocarbon with unique acidic or redox properties. [ABSTRACT FROM AUTHOR]

A composite catalyst including palladium nanoparticles on titania (TiO2) and on nitrogen-modified porous carbon (Pd/TiO2@NC) is synthesized from palladium salts, tetrabutyl titanate, and chitosan. N2 sorption isotherms show that the catalyst has a high BET surface area (229 m2 g−1) and large porosity. XPS and TEM characterization of the catalyst shows that palladium species with different chemical states are well dispersed across the TiO2 and nitrogen-modified porous carbon, respectively. The Pd/TiO2@NC catalyst is very active and shows excellent stability towards hydrogenation of vanillin to 2-methoxy-4-methylphenol using formic acid as hydrogen source. This activity can be attributed to a synergistic effect between the Pd/TiO2 (a catalyst for dehydrogenation of formic acid) and Pd/NC (a catalyst for hydrogenation of vanillin) sites. [ABSTRACT FROM AUTHOR]

Abstract: Electron microscopy (EM) enables us, not only to reveal the morphology, but also to provide structural, chemical and electronic information about solid catalysts at the atomic level, providing a dramatic driving force for the development of heterogeneous catalysis. Almost all catalytic materials have been studied with EM in order to obtain information about their structures, which can help us to establish the synthesis–structure–property relationships and to design catalysts with new structures and desired properties. Herein, several examples will be reviewed to illustrate the investigation of catalytic materials by using electron beams. [Copyright &y& Elsevier]

Ketonic carbonyl groups are catalytic active sites for oxidative dehydrogenation (ODH) reactions on carbon nanotubes. The quantity of these groups could be calculated from chemical titration with hydrazine compounds. ODH catalytic activity of nanocarbon is directly correlated with surface concentration of ketonic carbonyl groups, and the turnover frequency normalized by the number of active sites reflects the intrinsic activity of nanocarbon catalysts. [ABSTRACT FROM AUTHOR]

Foam party: A new method is reported for the immobilization of carbon nanotubes (CNTs) onto silicon carbide foam to afford a CNT/SiC monolith catalyst for sustainable chemistry applications. The as‐synthesized monolith displayed good stability and high catalytic performance in the oxidative dehydrogenation (ODH) of 1‐butene into butadiene. [ABSTRACT FROM AUTHOR]

Leaping the dragon gate Nanoscale phase transitions occur for a ZnO‐supported PdZn intermetallic under realistic acetylene hydrogenation conditions. In their Communication on page 4232 ff., D. S. Su, W. Zhang, B. Zhang, et al. observe the evolution of a PdHx intermediary species at the interface between PdHx and a ZnO support using in situ X‐ray diffraction and transmission electron microscopy. According to Chinese legend, Yulong carp will transform into dragons if they climb a waterfall. [ABSTRACT FROM AUTHOR]

Review: 69 refs. [ABSTRACT FROM AUTHOR]

Controllable synthesis of well‐defined supported intermetallic catalysts is desirable because of their unique properties in physical chemistry. To accurately pinpoint the evolution of such materials at an atomic‐scale, especially clarification of the initial state under a particular chemical environment, will facilitate rational design and optimal synthesis of such catalysts. The dynamic formation of a ZnO‐supported PdZn catalyst is presented, whereby detailed analyses of in situ transmission electron microscopy, electron energy‐loss spectroscopy, and in situ X‐ray diffraction are combined to form a nanoscale understanding of PdZn phase transitions under realistic catalytic conditions. Remarkably, introduction of atoms (H and Zn in sequence) into the Pd matrix was initially observed. The resultant PdHx is an intermediate phase in the intermetallic formation process. The evolution of PdHx in the PdZn catalyst initializes at the PdHx/ZnO interfaces, and proceeds along the PdHx ⟨111⟩ direction. A palladium catalyst supported on ZnO is monitored in situ and in chemical environments relevant to catalysis. Structural evolution of PdZn intermetallic metal nanoparticles (NPs), visualized at an atomic scale, reveals the evolution of a PdHx intermediary species at the interface between PdHx and the ZnO support. [ABSTRACT FROM AUTHOR]

The surface chemistry of nanocarbon support can tailor chemical properties of precious metal nanoparticle/nanocarbon hybrid catalyst in heterogeneous reactions. We report on modified reduced graphene oxide (rGO) support with ionic liquid-derived carbonaceous surface for palladium nanoparticle (Pd NPs) decoration and their actions in different heterogeneous reactions. The surface chemistry of support materials was characterized in detail, and the influence of which on the formation and distribution of metal particles was further investigated. Three different types of reactions including Suzuki-Miyaura coupling reaction, CO oxidation and phenol reduction were examined in terms of reactivity and selectivity. The roles of substituted nitrogen in graphitic lattice and grafted groups on the carbon surface were exploited. Nitrogen-doping can give rise to changes in electronic properties of supported metals, and the Lewis basicity of the doped nitrogen atoms can favor the adsorption of acidic reactants in phenol reduction. The grafted groups derived a negative impact to the Suzuki-Miyaura coupling reaction, due to the involvement of larger reactant molecules, despite that they could prevent significant sintering of Pd NPs in the CO oxidation. [ABSTRACT FROM AUTHOR]

Howto achieve supported metal nanocatalysts with simultaneously enhancedactivity and stability is of vital importance in heterogeneous catalysisand remains a challenging goal. In this work, a surface defect-promotedNi nanocatalyst with a high dispersion and high particle density embeddedon a hierarchical Al2O3matrix was fabricatedvia a facile method involving an in situ reduction process, whichexhibits excellent activity and stability simultaneously for the reactionof CO2methanation. HRTEM, HAADF-STEM, EXAFS, and positronannihilation spectroscopy demonstrate the existence of abundant surfacevacancy clusters that serve as active sites, accounting for the significantlyenhanced low-temperature activity of the supported Ni nanoparticles.In addition, the anchoring effect from the support gives rise to ahigh reaction stability, without sintering and/or aggregation of activespecies during long-term use. [ABSTRACT FROM AUTHOR]