The rate of oxygen permeation through La1−xSrxCo1−yFeyO3−δ was found to increase with an increase in Sr or Co content, showing that the permeability was mainly controlled by the amount of oxygen vacancies. The results obtained indicate that mixed conductive perovskite-type oxides are promising materials for oxygen permeation at elevated temperatures.

An overview of the catalytic properties of intermetallic compounds has been made to provide a comprehensive understanding regarding (1) what intermetallic catalysts can do, (2) their fundamental roles in enhanced catalysis, and (3) their advantages over other inorganic materials. A number of chemical transformations using intermetallic catalysts have been surveyed and classified into three major divisionshydrogenation/dehydrogenation, oxidation, and steam reforming and various subsections. The fundamental roles of intermetallic phases obtained from this survey were categorized into four types of effects: (a) electronic, (b) geometric, (c) steric, and (d) ordering effects. The unprecedented steric effects governed by the specific surface structures of intermetallic compounds highlight the unique capabilities of intermetallic materials. On the basis of this overview, we have concluded that intermetallic compounds have the following advantages for fine catalyst design: (i) control of the electronic structure, (ii) a specific and ordered atomic-level structure, and (iii) homogeneity of geometric and electronic structures. Thus, intermetallic compounds are promising inorganic catalyst materials capable of creating a well-designed reaction environment and suitable for developing efficient catalytic systems.

b S Supporting Information O xidation of amine to imine is an important chemical transformation because of the versatile applications of imines as synthetic intermediates of medicines or biologically active nitrogen containing organic compounds. 1 Several oxidation procedures using stoichiometric oxidants such as 2-iodoxybenzoic acid 2,3 or N-tert-butylphenylsulfinimidoyl chloride 4 have been reported. However, a catalytic system using molecular oxygen as a sole oxidant has been desired in view of green chemistry. 5,6 In this context, a number of transition-metal catalyzed aerobic oxidation systems have been developed. Ru-based catalysts such as RuCl 3 , 7 [RuCl 2 (RCH 2 NH 2 ) 2 (PPh 3 ) 2 ], 8,9 Ru-porphyrin, 10 Ru-hydroxyapatite, 11 Ru 2 (OAc) 4 Cl, 12 and Ru/Al 2 O 3 13 are known to be effective for aerobic oxidation of amines. Au nanoparticles supported on Al 2 O 3 , 14,15 CeO 2 , 14,15 graphite, 16 and hydroxyapatite 16 are also found to be good catalysts for amine oxidation. But in these systems, expensive precious metals are employed and relative high temperature (mostly >373 K) is required.Utilizing semiconductor photocatalysts for aerobic oxidation of organic molecules has practical advantages of economical efficiency, environmental-friendliness, reusability, and durability. In addition, to effectively utilize solar energy, it is necessary to develop a material that will function under visible light. 17 Very recently, Su and co-workers reported that mesoporous graphite carbon nitride (mpg-C 3 N 4 ) can work as effective photocatalyst to activate O 2 for the selective oxidations of benzylic alcohols and amines with visible light. 18,19 Although this material exhibits excellent catalytic performance under visible light irradiation, high oxygen pressure (0.5 MPa) and trifluorotoluene as solvent are necessary to obtain good yields. Zhao et al. reported that photooxidation of amines using TiO 2 with UV light gave a high selectivity to imines under a diluted condition. 20 We recently reported that photocatalytic oxidation of various alcohols proceeded selectively over niobium oxide (Nb 2 O 5 ) under a mild condition. 21,22 Nb 2 O 5 showed higher selectivities to partial oxidation products; therefore, it can be thought that Nb 2 O 5 is more suitable for selective oxidation than TiO 2 . Moreover, we found that Nb 2 O 5 can catalyze the selective photooxidation of alcohols even under visible light

The upgrading of plastic waste is one of the grand challenges for the 21 st century owing to its disruptive impact on the environment. Here,w es howt he first example of the upgrading of various aromatic plastic wastes with C À Oand/or C À Cl inkages to arenes (75-85 %y ield) via catalytic hydrogenolysis over aR u/Nb 2 O 5 catalyst. This catalyst not only allows the selective conversion of single-component aromatic plastic,a nd more importantly,e nables the simultaneous conversion of am ixture of aromatic plastic to arenes.T he excellent performance is attributed to unique features including:(1) the small sized Ru clusters on Nb 2 O 5 ,whichprevent the adsorption of aromatic ring and its hydrogenation;(2) the strong oxygen affinity of NbO x species for C À Ob ond activation and Brønsted acid sites for CÀCb ond activation. This study offers ac atalytic path to integrate aromatic plastic waste back into the supply chain of plastic production under the context of circular economy.

Propylene production via propane dehydrogenation (PDH) requires high reaction temperatures to obtain sufficient propylene yields, which results to prominent catalyst deactivation due to coke formation. Developing highly stable catalysts for PDH without deactivation even at high temperatures is of great interest and benefit for industry. Here, we report that single-atom Pt included in thermally stable intermetallic PtGa works as an ultrastable and selective catalyst for PDH at high temperatures. Intermetallic PtGa displays three-hold-Pt ensembles and single Pt atoms isolated by catalytically inert Ga at the surface, the former of which can be selectively blocked and disabled by Pb deposition. The PtGa-Pb/SiO2 catalyst exhibits 30% conversion with 99.6% propylene selectivity at 600 °C for 96 h without lowering the performance. The single-atom Pt well catalyzes the first and second C–H activation, while effectively inhibits the third one, which minimizes the side reactions to coke and drastically improves the selectivity and stability.

The surface oxygen vacancy formation energy (E Ovac ) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine E Ovac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence E Ovac . Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O 2 , NO, CO, CO 2 , and H 2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and E Ovac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.

Nanoparticulate intermetallic PtZn acts as a highly efficient heterogeneous catalyst for chemoselective hydrogenation of halonitrobenzenes to haloanilines. Chloroanilines, bromoanilines, and iodoanilines, including all regioisomers, were obtained with excellent yields (typically >99%) under 1 atm H 2 at 40°C. A gram-scale reaction afforded a turnover number (TON) of 8600. PtZn/SiO 2 could be reused at least four times without significant loss of catalytic performance. PtZn/SiO 2 afforded 7-fold higher TOF than Pt/ SiO 2 . A combination of kinetic analysis, X-ray photoelectron spectroscopy (XPS) studies, and density functional theory (DFT) calculations revealed that electron-enriched Pt by Zn not only promotes nitro-hydrogenation but also effectively inhibits the carbon−halogen bond scission.H aloanilines (HANs) are valuable intermediates in the synthesis of various chemicals, such as pharmaceuticals, dyes, pigments, and pesticides. 1,2 HANs have been conventionally synthesized from corresponding halonitrobenzenes (HNBs) with stoichiometric reductants such as Fe−HCl (via the Bećhamp process), 3 Sn−HCl, 4 or hydride reagents. 5 However, these processes generate stoichiometric amounts of harmful chemical wastes including metal salts. In the principle of high atom efficiency and green chemistry, these stoichiometric systems have been expected to be replaced by heterogeneous catalytic systems, using transition metals and gaseous hydrogen. The heterogeneous hydrogenation of HNBs to HANs involves the intrinsic difficulty of inhibiting the hydrogenolysis of the weak carbon−halogen (C−X) bond, resulting in dehalogenation and loss of the HAN yield. 2,6 This undesired side reaction becomes more prominent and unavoidable as the C−X bond becomes weaker from C−Cl to C−I. The weaker C−X bonds of iodoanilines (IANs) and bromoanilines (BANs), compared with those of chloroanilines (CANs), are greatly valuable in organic synthesis reactions including various coupling reactions. 7,8 Therefore, achieving the selective hydrogenation of iodonitrobenzenes (INBs) and bromonitrobenzenes (BNBs) in the synthesis of the corresponding HANs is not only challenging but also highly demanding. To date, however, attempts to develop a highly selective HNB hydrogenation with heterogeneous catalysts and H 2 have been focused on chloronitrobenzenes (CNBs). 9,10 In this context, devising a highly efficient heterogeneous catalyst for HNB hydrogenation with a wide substrate scope has a great potential for future applications.Existing strategies for heterogeneous CNB hydrogenation have been based on the use of bimetallic materials, which typically comprise noble metals (Pt, Ir) and/or base metal oxides (TiO 2 , 11−13 FeO x 14−17 ). The bimetallic interface appears to provide electronically modified noble metals suitable for selective CNB hydrogenation. 12,15 However, a simple bimetallic composite provides a limited number of interfacial sites and nondrastic electronic modification, which hamper further improvements in the catalytic performance and substra...

Intermetallic Pd3Pb supported on Al2O3 can act as a highly efficient heterogeneous catalyst for the oxidation of various amines including primary, secondary, aromatic, aliphatic, and cyclic amines.