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The fabrication of noble metal free catalysts with excellent performance and high stability by a simple, efficient, general and low-cost approach remains an urgent task for solving the problem of resource shortage. Herein, Cu-based metal organic frameworks (MOFs) immobilized on commercial filter papers were used as pyrolysis precursors to synthesize CuxO@C at various calcination temperatures. Notably, the resultant CuxO@C-400 exhibits an excellent catalytic performance toward the reaction of reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). By virtue of the large specific surface area, well-developed porosity, good stability and high dispersity of CuxO nanoparticles, the obtained CuxO@C-400 could complete the reduction reaction within 11 min with a large apparent rate constant κapp value (4.8 × 10−3 s−1). Our strategy therefore opens a new avenue for the preparation of low-cost and high-performance noble metal free catalysts. [ABSTRACT FROM AUTHOR]

The Pt–V bimetallic catalytic system may be a promising alternative to noble metal catalysts for selective catalytic oxidation (SCO) of NH3. But it is challenging to improve the NH3 conversion activity and N2 selectivity, as well as cost-economy. Herein, the influence of the deposition order of V and Pt components on NH3-SCO performance was investigated with constant loadings of 0.5 wt% V and 0.04 wt% Pt. The catalytic performance of the Pt–V system significantly depended on the combination mode between VOx and Pt species. The V0.5/Pt0.04/TiO2 catalyst exhibited outstanding NH3-SCO performance, giving complete NH3 conversion and 80.2% N2 selectivity at 225 °C. This was ascribed to a preferable synergistic effect between the upper layer of VOx species and the lower layer of Pt species supported on TiO2. This led to more abundant Pt0 species in the lower layer, which was favorable for oxidizing the diffused NH3 efficiently into N2, H2O and some NOx. The generated NOx would further react with fresh NH3 in an efficient way under the action of VOx species in the upper layer via selective catalytic reduction (SCR) reactions owing to the excellent redox ability of the V0.5/Pt0.04/TiO2 catalyst. –NH2 species and nitrate species were the main intermediates participating in the NH3-SCO reactions over the V0.5/Pt0.04/TiO2 catalyst. [ABSTRACT FROM AUTHOR]

Graphdiyne (GDY), a novel two-dimensional (2D) carbon material with sp- and sp2-hybridized carbon atoms, has earned a lot of attention in recent years. Owing to its low reduction potential and highly conjugated electronic structure, it can be used as a reducing agent and stabilizer for the electroless deposition of highly dispersed Au nanoparticles. In this paper, we observe that exfoliated GDY (eGDY), the exfoliation of bulk GDY into single- or few-layered GDY in aqueous solution, can be used as an excellent substrate for the electroless deposition of very small Au nanoparticles to form a Au/eGDY nanocomposite that exhibits higher catalytic performance for the reduction of 4-nitrophenol. The higher catalytic performance is considered to arise from the high specific surface area of eGDY and the electroless deposition of active metal catalysts with eGDY as the support. Our results inspired the present investigation into the use of eGDY for the development of highly efficient catalysts. [ABSTRACT FROM AUTHOR]

The development of efficient carbon dioxide reduction reaction (CO2RR) catalysts is one of the practical solutions to the current environmental problems. Usually, metal-doped catalysts are used for the CO2RR, but the metal elements can easily aggregate, resulting in a reduction in the catalytic performance. In this study, NiFe-LDH was exfoliated to single layer by a solid-phase exfoliation strategy, wherein Ni and Fe were doped on the char material owing to the pyrolysis of the solid-phase exfoliation agent, and the NiFe-CN catalyst with a gauzy and porous structure was obtained. The catalyst possessed excellent catalytic performance; particularly, when the mass fraction of NiFe-LDH was 1 wt%, the prepared catalyst (NiFe-CN-1) showed a faradaic efficiency of 93.5% for the reduction of CO2 to CO at −0.8 V (vs. reversible hydrogen electrode (RHE)) with a CO current density of 10.4 mA cm−2, which was due to the sufficient exposure of active sites and efficient proton transfer channels of NiFe-CN. This strategy provides a new idea to easily mass produce CO2RR electrocatalysts in an environmentally benign way. [ABSTRACT FROM AUTHOR]

NOx is one of the most severe air contaminants, which mainly comes from fixed sources and has a tremendous negative impact on public health and regional air quality. The treatment of NOx has become an important issue. Among numerous NOx emission control technologies, selective catalytic reduction using ammonia as the reducing agent (NH3-SCR) is regarded as the most effective and mature technique with 40 years of development. Currently, commercial NH3-SCR catalysts are mainly vanadium-based catalysts; however, V2O5 is identified as a biotoxic species. A cerium-based catalyst is a kind of environment friendly catalyst for NH3-SCR. However, exhaust gas usually contains a small amount of SO2 and H2O vapor under actual conditions, inhibiting the NH3-SCR reaction with cerium-based catalysts. Therefore, improving the resistance of SO2 and H2O of cerium-based catalysts has become a research hotspot in recent years. This review presents a unified discussion of the significant work published in the field of the resistance of SO2 and H2O of cerium-based catalysts for NH3-SCR. It emphasizes the reaction mechanism and aspects of cerium-based catalysts at different levels: metal modification, preparation methods, and structures. The discussion is then extended to the essential conclusions from cerium-based catalyst modification and recommendations for future directions to develop a catalytic system that will degenerate NOx over non-noble metal catalysts with high resistance of SO2 and H2O. [ABSTRACT FROM AUTHOR]

The reaction mechanism for the full hydrogenation of 2-phenyl-6-methyl-pyridine catalyzed by the Lewis acid C6F5(CH2)2B(C6F5)2 was investigated in detail by density functional theory calculations. Our calculations show that a plausible reaction pathway of the hydrogenation of pyridine contains five stages: (1) the generation of a new borane C6F5(CH2)2B(C6F5)2 from the hydroboration of the alkene, which forms a frustrated Lewis pair (FLP) with a pyridine; (2) the activation of H2 by FLP to yield an ion pair intermediate; (3) intramolecular hydride transfer from the boron atom to the pyridinium cation in the ion pair intermediate to produce the 1,4-dihydropyridine; (4) hydrogenation of the 1,4-dihydropyridine by the FLP to form the 1,4,5,6-tetrahydropyridine; (5) hydrogenation of the 1,4,5,6-tetrahydropyridine by the FLP to yield the final piperidine. The last two hydrogenation processes follow a similar pathway, which includes four steps: (a) proton transfer from the pyridinium moiety to the substrate; (b) dissociation of the newly generated pyridine; (c) hydride migration from the hydridoborate moiety to the protonated substrate to produce the hydrogenated product; (d) release of the hydrogenated product to regenerate the free borane. The full hydrogenation of pyridine is calculated to be exothermic by 16.9 kcal mol−1, relative to the starting reactants. The rate-limiting step is the proton transfer in the second hydrogenation step, with a free energy barrier of 28.2 kcal mol−1 in the gas phase (27.9 kcal mol−1 in toluene) at room temperature and 1.0 atm. Our results can account for the observed experimental facts. [ABSTRACT FROM AUTHOR]