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Co-B catalyst, W-modified Co-B (Co-W-B) catalyst, and Mo-modified Co-W-B (Co-W-Mo-B) catalyst powders were synthesized via chemical reduction of metal salt solutions at room temperature. The optimal hydrogen production rate was obtained when the ratio of the reducing agent (NaBH4) to the metal solution was 4:1. Among the ternary catalysts, the Co0.1-W0.9-B catalyst showed the optimal hydrogen production rate when the content of W doping was 0.9. Furthermore, the hydrogen production rate of the quaternary catalyst was enhanced when the content of Mo doping was 0.075, denoted as Co0.1-W0.9-Mo0.075-B. The catalyst powders were characterized by SEM, XRD, XPS, and BET. The hydrogen production rates of the Co-B catalyst, Co0.1-W0.9-B catalyst, and Co0.1-W0.9-Mo0.075-B catalyst were investigated for the decomposition of alkaline sodium borohydride (NaBH4) in a water–ethanol mixture solution. The Co0.1-W0.9-Mo0.075-B catalyst exhibited the highest hydrogen production rate compared to Co-B and Co0.1-W0.9-B catalyst powders. The optimal hydrogen production rate of the Co0.1-W0.9-Mo0.075-B catalyst is 4600 ml·min−1·g−1, which is nearly 1.9 times higher than that of the Co-B catalyst. Moreover, the Co0.1-W0.9-Mo0.075-B catalyst exhibited good stability, retaining 73% of its catalytic activity after five cycles, and had a low apparent activation energy of 41.51 kJ·mol−1. [ABSTRACT FROM AUTHOR]

A series of mesoporous nanoparticle P-CexZr1-xOy (PCZ) catalysts with abundant oxygen vacancies and high specific surface area were successfully prepared, exhibiting 100% formaldehyde conversion at room temperature (25 °C). The PCZ catalyst was investigated in depth utilizing TEM, BET, XRD, XPS, H2-TPR, and Raman characterization, it was found that the PCZ catalyst had an average particle size of 10 nm and a specific surface area of 108 m2/g; templating caused by P123 and effective doping of Zr atoms regulated the oxygen vacancies in the catalyst, altered the reduction characteristics and chemical state of cerium to formed the redox cyclic couple of Ce3+/Ce4+, which significantly enhanced the catalytic oxidation performance of the PCZ catalyst in the indoor environment. [ABSTRACT FROM AUTHOR]

The application of zero-valent iron nanoparticles (nZVI) is an area of growing interest, especially in the remediation processes of waters of different origin. The standard synthetic procedure for nZVI involves the chemical reduction of Fe2+ or Fe3+ with the solution of a strong reducing agent. This type of synthetic route leads to the formation of new toxic species. The green synthesis of nZVI using plant extracts is, therefore, an excellent alternative to the above-mentioned conventional methods. Within the scope of this work, the amorphous nZVI was synthesized by green tea mediated single-step method from Fe3+ as precursors, denoting an eco-friendly approach. Additionally, the physico–chemical characterization (TEM, SEM/EDS, size of particles/aggregates, XRD, BET) of nZVI was performed. The catalytic activity of the obtained nZVI was tested in a Fenton-like reaction of the removal/degradation of three representative industrial textile dyes (methylene blue, methyl orange and bromothymol blue) from water. In order to optimize the process parameters, the effect of homogenization treatment, nZVI and H2O2 concentration on catalytic performance were also done followed by degradation kinetic study using four different models. The results of this work have shown the exceptionally high efficiency of the green nZVI which is reflected in almost complete degradation of all tested dyes within very short period of time, despite their amorphous nature, aggregates arrangement and very low specific surface area. Furthermore, the examined degradation kinetics has excellently followed the BMG model, indicating that the degradation process of the investigated dyes proceeds via two stages (two-stage pattern)—a fast one and a much slower one, regardless of the used reaction conditions. Based on all gained results, particular degradation mechanisms were proposed. [ABSTRACT FROM AUTHOR]

Core–shell structure Cu@Pd/C catalysts were prepared in two steps combining microwave-assisted glycol reduction and chemical impregnation method for the first time. Compared with the traditional one-step synthesis of PdCu/C alloy catalysts by microwave (marked as M-PdCu/C) and impregnation (denoted by I-PdCu/C) method, respectively. The Cu@Pd/C catalysts were prepared in two-step show better catalytic performance toward formic acid oxidation, due to its special core–shell structure and better dispersion. On this basis, different proportions of Cux@Pdy/C (x:y = 1:1, 1:2, 1:3, 1:4 and 1:5) catalysts were synthesized by the two-step strategy. The relationship between lattice strain, electron distribution and catalytic performance were explored by physical and chemical characterization. X-ray diffraction and X-ray photoelectron spectra analyses showed that the introduction of Cu lead to the lattice contraction and modified electronic structure of Pd. The electrochemical test showed that Cu@Pd3/C sample has the highest activity toward formic acid electro-oxidation. Its mass activity is about 3.3 times that of Pd/C catalyst that was synthesized by impregnation method (labelled as I-Pd/C). At the same time, the Cu@Pd3/C catalyst also demonstrated improved stability. The low-palladium catalyst with a Pd–Cu shell–core structure was synthesized by two-step method and has excellent catalytic activity and stability for formic acid electro-oxidation. [ABSTRACT FROM AUTHOR]

The supported Ni-B/KIT-6 amorphous alloy catalyst was prepared by chemical reduction method for the hydrogenation reaction of α-pinene. The catalyst was characterized by XRD, BET, SEM–EDS, TEM, XPS, ICP and DLS, the influences of single factor of catalyst on its structure, morphology and performance were investigated and analyzed. It was found that the amount of Ni loading, preparation pH and B/Ni molar ratio had great effects on the reduction amount, dispersion and specific surface area of the catalyst, resulted in affecting the catalytic performance of the catalyst. The optimum synthesis conditions were at m(Ni2+)/m(KIT-6) = 1:3, pH 13 and n(B)/n(Ni) = 1.5, obtaining a 90.62% conversion of α-pinene and 97.67% selectivity of cis-pinane. In addition, the catalysts also exhibited better repeatability and stability. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells are promising electrochemical energy conversion devices. But, more efficient and stable and less expensive catalysts are still required. Here, we successfully synthesized Pt/C and Pt0.5–Ir0.5/C, Pt0.6–Ir0.4/C, Pt0.7–Ir0.3/C, and Pt0.8–Ir0.2/C nanowires by the chemical reduction of the metallic precursors by formic acid and tested them towards methanol electro-oxidation in acidic media. Neither surfactants nor templates were used during the syntheses. The nanowires catalysts were compared with a commercial state-of-art catalyst aiming the observation of the properties improvements derived from both alloying Pt with Ir and morphology change from nanoparticles to nanowires. Well-defined and slightly agglomerated over the carbon nanowires (diameters and lengths of approximately 5 and 20 nm, respectively) were obtained, the fact that is ascribed to the 40 wt% metal loading. In addition, accelerated degradation tests showed that Pt0.6–Ir0.4/C, Pt0.7–Ir0.3/C and Pt0.8–Ir0.2/C catalysts are more stable than commercial Pt/C. All synthesized nanowires catalysts were more active towards methanol electro-oxidation than the commercial Pt/C. The Pt0.5–Ir0.5/C sample shows Pt mass activities 7 times that of commercial Pt/C. However, the Pt0.8–Ir0.2/C catalyst presented the best specific activity (6 times that of commercial Pt/C), have the highest currents in the derivative voltammetry and the oxidation potential shifts negatively 100 mV in comparison with the commercial Pt/C catalyst. Hence, the nanowires developed in this study are indicated as potential promising catalysts and can be applied successfully as direct methanol fuel cell anodes. [ABSTRACT FROM AUTHOR]

Novel SOx-reducer (ReSOx) catalysts containing an Mg-Al-Fe anionic clay as precursor and primary constituent have been scaled-up for commercial application in fluid catalytic cracking (FCC). The catalysts are manufactured, on a large scale, through a facile, energy-wise, environment-friendly and economical procedure which, advantageously, does not require external binding agents to produce fluidizable microspheroidal particles. Ce is added into the catalysts' composition in varying amounts to extend their flexibility for usage in partial or full combustion regenerators. When tested industrially in a 40 MBPD (1000 barrels per day), 180 ton of catalyst inventory, partial combustion FCC unit, ReSOx-catalysts exhibit a notably high SOx reduction activity removing around 35 kg SO2 per kg of catalyst, without detecting upsets neither in the base cracking performance nor in coke production in a continuous 48-days run.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The various metal ratios of PdCoNi/G nanocomposites (PdCoNi/G 6:1:1, 6:3:3, 6:4.5:1.5, 6:1.5:4.5, and 6:9:9) supported on graphene were synthesized using a chemical reduction of metal compounds and graphite oxide with a strong reducing agent under N2 conditions without calcinations to improve the electrocatalytic performance for methanol electrooxidation. SEM, EDX, XRD, XPS, and XANES were used to study the physical and chemical properties of all electrocatalysts. The composition of PdCoNi/G electrocatalysts was in the form of palladium metal, cobalt oxides, and nickel oxide. The electrocatalysis activity of methanol oxidation in 1 M KOH was investigated by cyclic voltammetry and chronoamperometry. It was found that PdCoNi/G (6:1:1) nanocomposite enhanced the catalytic activity. The relative potential showed the highest current density (17.27 mA/cm2) and negative potential (− 0.065 V) in the catalyst studies. In addition, PdCoNi/G (6:1:1) nanoncomposite presented the best intermediate poisoning tolerance for the methanol oxidation of all synthesized electrocatalysts. These confirmed that PdCoNi/G (6:1:1) is very promising for applications in direct methanol fuel cell (DMFC).Graphical Abstract: Schematic illustration of the synthesis of PdCoNi metal nanocomposites (various metal ratios) supported on graphene (a) oxidation of graphite to GO and (b) reduction between GO and metal compounds with NaBH4 as a reducing agent. [ABSTRACT FROM AUTHOR]

Abstract: For the first time, the oxygen reduction reaction (ORR) is studied on pyrolysed electrospun multi-walled carbon nanotube (MWCNT) and styrene-acrylonitrile (SAN) composite fibre catalysts in alkaline medium. Scanning electron microscopy images revealed that the prepared catalysts mainly consist of MWCNTs, while nitrogen doping of the catalysts is confirmed by X-ray photoelectron spectroscopy. This indicates that SAN can be used as a nitrogen precursor. The ORR studies carried out by rotating disc electrode (RDE) and rotating ring-disc electrode (RRDE) methods showed that the prepared catalysts were considerably more active towards the ORR than the pristine MWCNTs.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: Ag nanoparticles incorporated β-cyclodextrin conjugated magnetic hydroxyapatite, γ-Fe2O3@HAp-CD.Ag was conveniently synthesized via the grafting of β-cyclodextrin moieties on the hydroxyapatite surface, followed by reacting of the nanocomposite, γ-Fe2O3, with silver nitrate and then its reduction with sodium borohydride. The cavity of β-cyclodextrin units as host material can stabilize the Ag nanoparticles (particles size: 12–14 nm) effectively and prevent their aggregation and separation from the surface. The nanocomposite obtained appears to have an organized structure, with a magnetic γ-Fe2O3 core surrounded by a layer-structured coating shell. The structure and composition of the nanocomposite were confirmed by FT-IR, FE-SEM, TEM, TGA, XRD, EDS, BET, and VSM. This catalytic system selectively reduces the nitro group even in the presence of other sensitive functional groups in good to excellent yields (85–98%).The organometallic nanocatalyst was easily removed from solution using an external magnet and was successfully examined for five runs, with a slight loss of catalytic activity.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Highly dispersed Pd nanoparticles (NPs) covered on amine-functionalized mesoporous hollow SiO spheres (Pd/MHSS-NH) have been successfully prepared. The morphology, structure and composition of Pd/MHSS-NH were characterized by Transmission electron micrograph (TEM), N ad-desorption, X-ray diffraction (XRD), Fourier-transfer infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The as-prepared Pd/MHSS-NH exhibited remarkably high activity for the reduction of 4-nitrophenol (4-NP) compared with other catalysts, which could be attributed to high dispersion of Pd NPs, amine functional groups on MHSS support, as well as mesoporous MHSS-NH shell. Additional, the Pd/MHSS-NH catalyst could be recovered by centrifugation from the reaction mixture and recycled six times without loss in activity. Graphical Abstract: [ABSTRACT FROM AUTHOR]

HCl electrolysis used to manufacture Cl, a compound of high industrial value, suffers from its high energy requirements. Significant energy savings can be attained by an alternative oxygen depolarized cathode (ODC)-based process where oxygen is reduced at the cathode instead of protons. Though the ODC process is extremely attractive, the state of the art catalysts for oxygen reduction reaction (ORR) suffer from chloride ion poisoning and/or involve toxic chemicals such as hydrogen sulfide (HS). In the present work, we demonstrate that non-metal containing CN catalysts do not get deactivated upon exposure to chloride ion environment unlike Pt/C or RhS/C where significant chloride ion poisoning was observed. The synthesis of these CN materials is also extremely facile and scalable. In addition, the performance of the synthesized CN catalysts was found to be very stable in HCl environment. Thus, the results presented here demonstrate the promise of CN materials as alternative catalysts for ODC-based HCl electrolysis process to manufacture Cl in a sustainable and safer way. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Pt-ZnO hybrid catalysts were synthesized via a facile wet chemical method for use in the photoenhanced selective hydrogenation of nitroarenes. The Pt-ZnO hybrid exhibited a good catalytic performance under UV irradiation. The reaction rate constant for the reduction of o-nitroaniline was significantly increased more than eight times upon UV illumination. This resulted from the increased photo-excited electron transport from ZnO to Pt interface, making electrons strongly perturb at the Pt surface to enhance hydrogen dissociation. Furthermore, we investigated the durable cyclic catalytic performance of the Pt-ZnO hybrid. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Pd-Ir mesocrystals with rough surface and highly branched structure were synthesized through a facile co-reduction method. The morphology evolution shows the mesocrystals were formed by oriented attachment of nanoparticles, and abundant defects sites as well as synergetic effect between building units were formed during mesocrystals oriented attachment process. Therefore, the supported Pd-Ir mesocrystals show a significant enhancement in catalytic performance in hydrogenation of 2-ethylanthraquinone compared with conventional Pd-Ir nanoparticles. The high activity can be ascribed to high densities of defect sites in Pd-Ir MCs catalyst, which facilitated H activation. In addition, the geometric effect of Pd-Ir MCs catalyst was responsible for inhibiting further hydrogenation of eAQH to undesired consecutive byproducts. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Cu/Zn/Al/Zr catalysts were prepared by liquid reduction method and tested for the synthesis of methanol by CO hydrogenation. With the purpose of relieving the aggregation of reduced Cu species, the order of calcination and liquid reduction process was modified. Catalysts with different thermal treatments were characterized by XRD, N physisorption, TEM, NO chemisorption, TG-MS, XPS, TPR, CO-TPD techniques. When liquid reduction was performed after calcination procedure, metallic Cu specific area and dispersion increased and the interaction among components was strengthened. The modified catalyst displays a slight superiority in CO conversion and methanol selectivity. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Cold-start emissions significantly contribute to total vehicular pollutant emission profiles. There has therefore been a significant amount of research focused on catalytic aftertreatment systems that can mitigate CO, hydrocarbon and NO emissions at low temperatures. Recently, passive NO adsorbers (PNAs) have been developed, and these can store or trap NO at low temperature and are designed to release the trapped NO at higher temperature ranges, where downstream NO reduction catalysts are active. Pd/BEA is reported to be one such PNA. In this study its NO storage at low temperatures and release at higher temperatures was characterized using temperature programmed (TP) experiments and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The influence of CO was investigated and was shown to improve the amount stored at low temperature and also induce higher temperature desorption, in a range that is applicable for downstream NO reduction. Without the reductant, NO release primarily occurred at temperatures too low to be practically relevant. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Dehydrogenation of propane to propene is one of the important reactions for the production of higher-value chemical intermediates. In the commercial processes, platinum- or chromium oxide-based catalysts have been used for catalytic propane dehydrogenation. Herein, we first report that bulk tungsten oxide can serve as the catalyst for propane dehydrogenation. Tungsten oxide is activated by hydrogen pretreatment and/or co-feeding of hydrogen. Its catalytic activity strongly depends on hydrogen pretreatment time and partial pressure of hydrogen in the feed gas. The activation of tungsten oxide by hydrogen is attributed to reduction of the metal oxide and presence of multivalent oxidation states. Comparison of the catalytic performance of partially reduced WO to other highly active metal oxides shows that WO exhibits superior catalytic activity and selectivity than CrO and GaO. The findings of this work provide the possibility for activation of metal oxides for catalytic reactions and the opportunity for the development of new type of catalytic systems utilizing partially reduced metal oxides. Graphical Abstract: [ABSTRACT FROM AUTHOR]

In this work, cysteine-functionalized FeO@Carbon magnetic nanoparticles were used for the synthesis of gold nanorods. FeO@C nanoparticles were first prepared by synthesis of FeO magnetic nanoparticles (MNPs), and then carbon-coated MNPs (FeO@C) were synthesized by glucose carbonization using a hydrothermal method. Finally, the gold NRs were loaded on the modified surface of FeO@C MNPs. The designed magnetically recoverable gold nanorods, after full characterization by FTIR, SEM, TEM, TGA, VSM, XRD, and ICP-OES, were applied to the reduction of nitroarenes. The FeO@C@Cys-Au nanorods showed higher performance than FeO@C@Cys-Au nanospheres in a selective facile reduction of nitroarenes to the corresponding aminoarenes in aqueous medium at room temperature using NaBH. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Monodispersed palladium nanoparticles (PdNp) have been synthesized by a green rapid bio-reduction method under room temperature and pressure. The reducing agents mainly involved in these processes are the various water soluble plant metabolites, polyphenols as well as co-enzymes present in the leaf extract of Tulsi ( Ocimum sanctum). An active and stable montmorillonite K-10 supported heterogeneous catalyst was prepared using these PdNp for oxidation of alcohols to their corresponding carbonyl compounds with efficient yield and having good reusability. These are characterized by TEM, XRD, BET surface area and UV-Vis absorption spectroscopy. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Herein, a facile chemical reduction technique was used to fabricate iron nanochains under room temperature. They show high adsorption capacity of 480 mg g and 100 mg L of Orange ΙΙ can be almost removed within 1 min. More important thing is iron nanochains can be recycled as a photo-Fenton catalyst to continuously degrade Orange ΙΙ. Specifically, 98% of Orange ΙΙ could be decomposed within 100 min under simulated solar light irradiation and 80% of the degradation rate was maintained even after 6 successive cycles, indicating its good photocatalytic performance and reusability. Hence, iron nanochains reported in the paper realize the maximum reusability of materials. Graphical abstract: An environment-friendly approach to fabricate iron nanochains as a superb adsorbent and recycled as a fine photo-Fenton catalyst. [ABSTRACT FROM AUTHOR]

Controlled synthesis of bimetallic catalysts has attracted much attention in heterogeneous catalysis because their catalytic activity depends on the size of nanoparticles and hence the methods of synthesis. In this work, one convenient method was proposed, with an aim to control the size and dispersion of bimetallic nanoparticles. In this method, Cu (or Ni) configurational ion of hydrotalcites was used as directing reagent, which directed the position and dispersion of the final bimetallic nanoparticles by employing the metal interaction between Cu and Au as the driving force. The size, structure and composition of bimetallic nanoparticles were characterized using techniques of X-ray diffraction (XRD), nitrogen physisorption, X-ray photoelectron spectra (XPS) and scanning transmission electron microscopy (STEM). The mean size of bimetallic AuCu nanoparticles was 2.5 nm, which was 1/4 (Step-impregnation) or 1/10 (Co-impregnation) of that prepared by traditional methods. Even if the loading of Au was increased to 10 wt%, the obtained AuCu nanoparticles were still well dispersed. The catalytic activity of AuCu and AuNi nanoparticles in aerobic oxidation of benzyl alcohol was far higher than those prepared by traditional methods. The mechanism of forming bimetallic nanoparticles was investigated. It was found that the dispersion of Cu (or Ni) and the interaction between Cu (or Ni) and Au are two key factors affecting the dispersion of AuCu (or AuNi) nanoparticles. Graphical Abstract: [ABSTRACT FROM AUTHOR]

N-doped TiO effectively extends the light response range of TiO photocatalysts from the ultraviolet to the visible region; a p-n heterojunction would favor the separation of photogenerated electron-hole pairs, leading to high quantum efficiency, and consequently, enhanced photocatalysis. A CuO/N-TiO hybrid catalyst with p-n heterojunctions was newly prepared using a solvothermal and chemical reduction method. The hierarchical structure and valence state of copper of the CuO/N-TiO catalyst have been confirmed using X-ray diffraction, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The hybrid CuO/N-TiO catalyst demonstrated good photostability and excellent photocatalytic activity toward H production, with a rate of 11 μmol g h under visible light irradiation (>400 nm) of a methanol aqueous solution. This offers an inexpensive and facile approach for potential efficient solar photon-driven H production. Graphical Abstract: [ABSTRACT FROM AUTHOR]

[Poly (N-Vinyl Pyrrollidone)] (PVP) (K30, average Mol. Wt., 40 kDa) stabilized gold nanoparticles with four different size (mean diameter) of 1.4 ± 0.2, 3.8 ± 0.4, 5.5 ± 0.8 and 7.8 ± 1 nm were synthesized using solution based chemical reduction method and used as catalysts for transfer hydrogenation reaction. Transfer hydrogenation of several organic functional groups (>C=O, -CH=O, -NO, -CH=CH, -C≡C-H, -C≡N) were studied using potassium formate (HCOOK) as hydrogen source in water. The major focus of this work was on catalytic activity, product selectivity and recycling ability of Au:PVP nanoparticles as a transfer hydrogenation catalyst. The size specific catalytic activity showed that up to 3.8 nm sized gold nanoparticles are highly active catalyst and afterwards its activity diminishes sharply with increasing particle size. Mechanistic insight showed that formate ions are activated on gold surface and produced bound hydride species, which is the active intermediate for this catalytic transformation. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Enantiomerically enriched aromatic secondary alcohols and its derivatives are important chiral intermediates utilized widely in pharmacy, chemical, hormone, spices and chiral auxiliary materials. Thus, the key factors affecting the asymmetric reduction were successfully analyzed using R. mucilaginosa CCTCC M2014255 resting cells. The optimal temperature, buffer pH, co-substrate and its concentration, resting cells concentration were systematically investigated. Under the optimized conditions, acetophenone and its derivatives were effectively asymmetrically reduced by R.mucilaginosa CCTCC M2014255 while the conversion reached >99.0 % and e. e. of product were >99.0 %, respectively. These results provide a theoretical and technical support for realizing industrialized production of enantiomerically enriched aromatic secondary alcohols by microbial catalytic asymmetric synthesis. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Bimetallic Cu@Au core/shell nanoparticles were prepared by the wet chemical reduction method using Tween as the organic modifier. The Cu@Au nanoparticles exhibited higher catalytic activity for the oxidation of 1,2-propanediol under mild reaction conditions than the sole Au nanoparticles. The Cu@Au nanoparticles with the mole ratios of Au to Cu of 0.015:0.985 and 0.035:0.965 exhibited high catalytic activities for the catalytic oxidation of 1,2-propanediol to lactic acid. A power function type reaction kinetic model well fitted the experimental data over the CuAu nanoparticle catalyst, r = - dn /( dt·W ) = kC P , and the reaction activation energy was 34.1 kJ mol. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Reverse water gas shift reaction (RWGS) was investigated over cerium oxide catalysts of distinct morphologies: cubes, rods and particles. Catalysts were characterized by X-ray diffraction, Raman spectroscopy and temperature programmed reduction (TPR) in hydrogen. Nanoshapes with high concentration of oxygen vacancies contain less surface oxygen removable in TPR. Cerium oxide cubes exhibited two times higher activity per surface area as compared to rods and particles. Catalytic activity of these nanoshapes in RWGS reaction exhibited a relation with the lattice microstrain increase, however a causal relationship remained unclear. Results presented in this study suggest that superior catalytic activity of ceria cubes in RWGS originates from the greater inherent reactivity of (100) crystal planes enclosing cubes, contrary to less inherently reactive (111) facets exposed at rods and particles. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Various single-phase aluminum oxides were prepared through the thermal decomposition of bayerite, boehmite, and gibbsite. Ni/γ-AlO and Ni/δ-AlO catalysts exhibited higher monoisopropylamine (MIPA) selectivity than the η-, θ-, and κ-AlO supported Ni catalysts for the reductive amination of 2-propanol (IPA) in the presence of hydrogen and ammonia. FT-IR spectra after pyridine adsorption showed that a high number of Lewis acid sites could be correlated with enhancement in MIPA selectivity. Ni/η-AlO and Ni/γ-AlO catalysts exhibited the highest catalytic activity arising from differences in the metallic surface area. Both catalyst activity and selectivity with regards to reductive amination were strongly affected by the nature of the support. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The present study shed light on synthesis, characterization and solar light induced catalytic activity studies for reduction of 4-nitrophenol by CeO and nano gold catalysts supported over CeO and CeO-TiO (1:1 mol ratio). The support systems were prepared by simple precipitation technique and the gold supported samples were synthesized using modified deposition-precipitation with urea method. The physicochemical characterization was performed by XRD, UV-Vis DRS, BET surface area, ICP-AES, TEM and XPS techniques. The catalytic performance of the synthesized catalysts were measured spectrophotometrically by engaging them for the reduction of 4-nitrophenol to 4-aminophenol in presence of NaBH serving as a hydrogen source. Au/CeO-TiO has been found to be a very effective catalyst showing ~100 % conversion in short reaction time. The catalytic activity of the Au/CeO-TiO showed no significant difference even after recycling the catalyst for four times indicating a promising potential for industrial application. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Poly(methylhydrosiloxane) [PMHS, R(OSiMeH)OR] is applied in chemistry as cheap, low-toxic, air and moisture stable reducing reagent. However, along with the desired products significant amounts of silicone waste is produced, since only ~1.7 % of the PMHS is employed for the reduction process. The formation of PMHS-waste reduces the sustainability of such reduction protocols. For instance PMHS can be applied as reagent (a) in the methanolysis to produce molecular hydrogen; (b) in the reduction of sulfoxides to form the corresponding sulfides; (c) in the hydrodeoxygenation of fatty esters to produce hydrocarbons. An option for the treatment of the PMHS-waste can be the application of depolymerization methods to convert it to useful commodities. In more detail, the silicone waste is reacted in a depolymerization reaction with boron trifluoride diethyl etherate (BFOEt) to produce methyltrifluorosilane (MeSiF) and difluoromethylsilane (MeSiFH), which can be interesting building blocks for the silicone industry, overall demonstrating a resource conserving process. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Platinum (II) tetrachloride (PTC) has been studied as an anionic metal precursor in strong electrostatic adsorption method of catalyst preparation. Compared to the conventionally used platinum (IV) hexachloride precursors, PTC exhibited greater pH stability in aqueous solution. As a result, PTC uptake on high PZC supports remained nearly unchanged irrespective of precursor aging. Upon reduction of these PTC catalysts small (~2.0 nm) and well-dispersed Pt nanoparticles were obtained on alumina, whereas on carbon, Pt sizes were significantly larger (4-10 nm). Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this study, a novel platelet-like nanocatalyst, Pd/g-CN with easily approachable active sites, was developed. The mesoporous graphitic carbon nitride (g-CN) is a layered structure connected by planar amino groups, which can work as stabilizer and active support for noble metal nanoparticles. The palladium nanoparticles with an average particle size of 3.25 nm were evenly dispersed on the surface of g-CN without aggregation. Detailed charaterizations reveal that there is no covalent-bond interaction between g-CN and Pd NPs. The Pd/g-CN catalyst showed excellent catalytic activity in the reduction of nitroarenes by NaBH, and Suzuki coupling reaction of aryl halides with arylboronic acids under mild conditions. The reduction of 4-nitrophenol has a pseudo-first-order rate constant of 7.29 × 10 s, and an activity parameter of 1.37 s mM, which is higher than those reported in the literature. Furthermore, the Suzuki coupling reactions processed smoothly with 97.0 % isolate yield in less than 30 min in water with PEG600 as the additive. The catalyst could be recycled for five times without significant loss of catalytic activity, which confirmed the good stability of the catalyst. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Copper nanoparticles (CuNPs) in aqueous medium were prepared with alkaline hydrazine hydrate as the reductant and PVP as the stabilizing agent without any inert gas protection. Careful variation in the amount of reductant resulted in formation of two stable CuNPs dispersions with different average sizes and consequently different localized surface plasmon resonance absorbances. These two as-synthesized CuNPs dispersions were used to catalyze the model p-nitrophenol reduction reaction. The kinetics of reduction was monitored as a function of concentration and temperature of reactants. Using this we determined the activation energy, pre-exponential factor and the entropy of activation for the two types of CuNPs samples. Catalytic activities of the CuNPs were found to be affected mainly by their activation energies. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Mn-Fe/AlO and Mn-Fe/TiO catalysts have been prepared by impregnation (IMP) and deposition precipitation (DP) and characterized with several techniques including: XRDP, N-physisorption, NH-TPD, H-TPR, TGA and XPS. 40 wt% MnFe/AlO prepared with ammonia carbamate as precipitating agent showed the same superior low temperature selective catalytic reduction of NO with NH as did 25 wt% MnFe/TiO prepared in the same way. Both catalysts were much more active when prepared by DP instead of IMP. 25 wt% MnFe/TiO and 40 wt% MnFe/AlO prepared by DP were exposed to a gas containing 20 vol% HO at temperatures between 140 and 200 °C and compared to an industrial VO-WO/TiO catalyst tested at 220 °C. Both homemade catalysts were severely inhibited by 20 vol% HO. However, used at 180 °C they match the activity of the industrial reference at 220 °C. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The Cu/Zn/Al catalysts, prepared from the calcination and reduction of hydrotalcite-like compounds containing Cu, Zn and Al, were introduced to the aqueous-phase hydrogenation of furfural from pyrolysis of biomass. And the target production was cyclopentanol. The catalyst performance was investigated from the aspects of catalyst composition, calcination temperature, reaction temperature, initial hydrogen pressure and reaction time. Among all the variables, calcination temperature had a profound impact on the catalyst performance. The furfural conversion was up to nearly 100 % with a cyclopentanol yield of 84 %, when the hydrogenation reaction was carried out over 600 °C calcined hydrotalcite catalyst with a Cu/Zn/Al molar ratio of 6:9:5 at 150 °C with an initial hydrogen pressure of 4 MPa for 10 h. The features of Cu/Zn/Al catalysts were investigated via XRD, XPS, TPR, SEM and BET. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Imidazolium salt stabilized copper nanoparticles were developed and characterized using TEM, DLS and EDX studies. Copper nanoparticles were further utilized as heterogeneous catalyst for the highly selective and efficient reduction of nitroarenes ( 1a- 10a) to the corresponding aromatic amines ( 1b- 10b) in aqueous medium. Imidazolium salt stabilized copper nanoparticles are not only causing the stability of the copper nanoparticles but also greatly enhancing the reactivity and selectivity of reduction reaction in presence of several functional group (-OH, -CHO and -NH) in aqueous medium with higher yield. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Iron(II) and palladium(II) phthalocyanines have been established as recyclable heterogeneous catalysts for the reduction of aromatic nitro compounds to corresponding amines using diphenylsilane/sodium borohydride as hydrogen sources in ethanol. Various reducible functional groups, such as acetyl, ester, cyano, amide, sulphonamide and carboxylic acid etc. were well tolerated, and the methods were applicable up to gram scale. Mechanistic studies showed that reduction of nitro group proceed through direct (nitroso) pathway and possibly iron or palladium phthalocyanines activates nitro group for reduction. FePc and PdPc also catalyzed the generation of hydrogen from the combination of diphenylsilane/sodium borohydride and ethanol. Graphical Abstract: Iron and palladium (II) phthalocyanines has been established as an efficient recyclable catalytic systems for reduction of nitroarenes with green solvent system. Various nitro substituted aromatics and heteroaromatics has been successfully reduced to corresponding amines in good to excellent yields. The present methods have also been productively applicable for gram scale reactions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Addition of hydrogen significantly increases the amount of stored nitrogen oxides (NO) over Pt/Ba/AlO at 100 °C and Ag/AlO between 100 and 200 °C. This increase is unique for hydrogen as reductant. A higher apparent NO storage capacity is also observed by simultaneous reduction of NO in a selective catalytic reduction (SCR) reaction, where, however, the conversion in H-SCR is <10 % in this study. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A series of highly active Pt-TiO catalysts have been prepared by impregnation methods via different reduction processes and used for catalytic decomposition of benzene. The oxidized and reduced Pt-TiO catalysts exhibit apparent differences in physical/chemical features (e.g. particle size, chemical state, and electronic property of Pt nanoparticles, and surface oxygen) and catalytic activities for benzene oxidation. Nearly 100 % benzene conversion is achieved on Pt-TiO catalysts obtained by the sodium citrate (CHNaO·2HO, NaCt) reduction at approximate 160 °C. Metallic Pt nanoparticles have strong capacity for oxygen activation, and the negative charges and rich chemisorbed oxygen on the surface of metallic Pt nanoparticles are probably responsible for their high catalytic activities for benzene oxidation. Graphical Abstract: 1 wt% Pt-TiO2 catalysts have been prepared by impregnation methods via different reduction processes and used for catalytic decomposition of benzene. The oxidized and reduced catalysts exhibit apparent differences in physical/chemical features and catalytic activities for benzene oxidation. Metallic Pt nanoparticles have strong capacity for oxygen activation, and the negative charges and rich chemisorbed oxygen on the surface of metallic Pt nanoparticles are probably responsible for their high catalytic activities for benzene oxidation. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Investigation of the polymerization of ethylene on CO-reduced Phillips catalyst (1 wt% chromium) by infrared spectroscopy reveals the presence of new OH bands. In particular, an OH-band appears at 3,605 cm, consistent with the interaction of the SiOH group with an adjacent Lewis acidic chromium center, Si-(μ-OH)-Cr. Polymerization with d-ethylene leads to the formation of the isotopically shifted band at 2,580 cm, consistent with heterolytic C-H activation of ethylene over a Cr-O bond to generate the first Cr-C bond in ethylene polymerization with Phillips catalyst, as recently observed on well-defined Cr(III) silicates. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have reported a LaMnO-based, Pt free lean NO trap (LNT) catalyst shows promising NO reduction activities, but the mechanism of NO reduction or the role of the perovskite over this catalyst has not been addressed. This paper presented our investigation on the mechanistic aspects of NO adsorption and reduction over several LaMnO-based LNT catalysts. NO can be effectively oxidized to NO on LaMnO at 350 °C, while little NO (NO + NO) can be stored verified by the following temperature programmed desorption experiment; under the same conditions, a significant amount of NO (41 μmol NO/g washcoat) were stored over BaO/AlO/LaMnO indicating NO are adsorbed mainly on the BaO/AlO. The temperature programmed surface reaction with CO demonstrated that although it can store NO during the lean period, failed to reduce NO by CO over the BaO/AlO/LaMnO catalyst. After adding Pd into BaO/AlO/LaMnO, NO can not only be stored during the lean conditions but also reduced. It could be concluded that the Pd catalyst, not perovskite, is responsible for NO reduction during the rich conditions. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The manifestations of strong and reactive metal-support interaction after reduction at elevated temperatures in Pt/VO and Pd/VO systems were studied using a dedicated thin film model system. Pt and Pd particles were prepared by electron-beam evaporation on NaCl(001) growth templates and subsequently embedded in a crystalline VO matrix, prepared by thermal evaporation of V metal in 10 mbar oxygen pressure. Template temperatures of 600 K were used to induce the formation of epitaxially-ordered metal-oxide systems. Engineering of the metal-support interface by distinct annealing treatments allows steering the extent and quality of metal-support interaction. Whereas for Pt/VO catalysts, high-temperature reduction at 773 K in hydrogen causes the epitaxial formation of a well-ordered body-centered tetragonal PtV intermetallic phase, the Pd/VO system is mostly unaffected by similar treatments and remains in a metal-oxide state. Nevertheless, oxidation at 773 K of both catalysts prior to the hydrogen treatments lifts the epitaxial relation between metal and oxide and in turn, subsequent reduction at high-temperatures (T ≥ 773 K) yields only polycrystalline PtV and PdV intermetallic phases without particular ordering with respect to the former growth substrate. Along with this formation of intermetallic phases goes a transformation of the support stoichiometry from VO to VO. Catalyst regeneration by partial oxidative decomposition of the intermetallic state is only possible at high-temperatures (T ≥ 750 K), yielding mostly metal particles and vanadium oxides with oxygen contents higher than V:O = 1:2, in particular VO. Graphical Abstract: Adjusting the extent of metal-support contact area by annealing treatments allows for easy steering the structure and morphology of well-defined intermetallic compounds in Pt-VO and Pd-VO systems. Well-defined PtV intermetallic compounds are formed by direct reduction, whereby lifting the ordering by pre-oxidation yields less-defined compounds with altered metal-support contact area and consequently, strong metal-support interaction. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A set of Au/C catalysts for the gas phase hydrochlorination of acetylene to vinyl chloride monomer were prepared using a range of strong acids as impregnating solvents and varying the preparation drying temperature. The most active catalyst is the material prepared using aqua regia as solvent with an intermediate drying temperature of 140 °C. The effects of the catalyst preparation parameters on the catalytic activity are examined using XPS and TPR as analytical tools. In particular, the use of thermal reduction methods allows the determination of kinetic parameters for the reduction of Au to Au by means of H. These data support the existence of a redox cycle between Au/Au when carbon is used as support. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Ni/γ-Al 2O 3 catalysts with different nickel loadings (4–27 wt%) were used for the synthesis of monoisopropylamine by the reductive amination of 2-propanol in the presence of hydrogen and ammonia. H 2-chemisorption analysis indicated that the highly reduced nickel metal surface area could be correlated with the enhancement of the 2-propanol conversion. During the reaction, the catalyst was progressively deactivated in the absence of hydrogen but its initial activity was completely recovered by re-exposure to the feed containing hydrogen. The deactivation was due to the formation of surface nickel nitride and excess hydrogen hindered the phase transition of the nickel metal to the corresponding nitride, ultimately preventing deactivation. Graphical Abstract: [InlineMediaObject not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Toluene oxidation was measured over Pt nanoparticles synthesized using a modified polyol reduction method and deposited on ionically conductive yttria-stabilized zirconia (Pt/YSZ) for three different loadings (1.1, 0.8, 0.4 %), and non-ionically conductive γ-alumina (Pt/γ-AlO) as a comparison (metal loading 0.7 %). It was found that nanoparticles supported on YSZ, tested as a support for the first time for toluene oxidation, have greater catalytic activity compared to a conventional γ-AlO support in spite of a lower specific area and Pt dispersion. This could be explained by the stronger metal-support interactions between Pt and YSZ due to the ionic conductivity of YSZ and presence of oxygen vacancies. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Synthesis of monodisperse Pt nanocrystals with cubic and cuboctahedral shapes were successfully done by using a chemical reduction method. The catalytic performance of Pt nanoparticles toward methanol electrooxidation was measured. The results indicate that Pt cuboctahedra with external Pt{100} and Pt{111} crystallographic facets showed a higher catalytic activity for methanol electrooxidation than the commercial Pt/C catalyst. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The well-defined piano-stool iron(II) complex (Cp-NHC)Fe(CO)I bearing a bidentate cyclopentadienyl-functionalised N-heterocyclic carbene ligand is shown to catalyse the reduction of ketones under mild conditions (1-2 h at room temperature) when combined with catalytic amounts of potassium tert-butoxide, and using PhSiH and the inexpensive and less reactive polymethylhydrosiloxane as reducing agents. The stoichiometric reaction of (Cp-NHC)Fe(CO)I with potassium tert-butoxide generates an iron-hydroxo complex, which seems to be the active species in the reduction of ketones. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A new inorganic material was used to produce hydrogen in situ by contact with water for reduction of unsaturated hydrocarbons. Phenylacetylene reduction into styrene and ethylbenzene was chosen as a model reduction reaction. We show that a fine control over the reaction yield and selectivity can be obtained by controlling the hydrogen release and such parameters of the synthesis as the temperature, water content and the speed of stirring. We found that the largest amount of water at 80 °C and vigorous stirring result in the highest yield and selectivity of the reaction. An alternative way of reaction control is suggested as compared to a conventional way of a catalyst inhibition. The new possibility of the reaction control may be of a wide interest for the laboratory synthesis for a good number of hydrogenation reactions. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have used density functional theory calculations to study intermediates in the electroreduction of methanediol on copper. We find that methanediol, which is the hydrated form of formaldehyde, may be reduced to methanol with a limiting potential close to the experimental onset for reduction of aqueous formaldehyde. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Rhodium nanoparticles were prepared by chemical reduction of RhCl·3HO in presence of polyvinyl pyrrolidone and then immobilized on SBA-15 by impregnation. The catalyst was used for hydrogenation of unsaturated hydrocarbons at room temperature. The progress of the reaction was monitored by GC-MS and 100 % conversion was achieved in all cases. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A palladium containing metal-organic framework (MOF) compound has been synthesized from MOF, (ZnO)(BDC-NH)(BTB) through Schiff base condensation reaction and complexation of Pd(II). Pd-MOF was found to be an effective heterogeneous catalyst for the oxidation and hydrogenation of various substrates under mild reaction conditions. This catalytic method is highly active and shape selective. Graphical Abstract: [InlineMediaObject not available: see fulltext.] [ABSTRACT FROM AUTHOR]