In Situ Generation of Pd-Pt Core-Shell Nanoparticles on Reduced Graphene Oxide (Pd@Pt/rGO) Using Microwaves: Applications in Dehalogenation Reactions and Reduction of Olefins

Comparative study of NiO/CuO/Ag doped graphene based materials for reduction of nitroaromatic compounds and degradation of dye with statistical study

In the present work, the Nickel oxide (rGO-NiO), Silver (rGO-Ag), Copper oxide (rGO-CuO) doped Graphene Oxide are reported for catalytic reactions. A comparative study for catalytic activities of these materials are performed with nitroaromatic compound 4-nitroaniline and the results are statistically studied by using univariate analysis of variance and Post Hoc Test through Statistical Package for Social Sciences and it is observed that CuO doped Graphene material is showing better catalytic activity in minimum time. So, further research has been focused on the catalytic acitivity of rGO-CuO only and it is found that it is efficient in reducing other nitro compounds also such as Picric acid and Nitrobenzene. Dye degradation of Methylene blue is also performed using CuO decorated Graphene material and significant changes were observed using UV spectroscopy. The characterization of rGO-CuO is done with Fourier-transform Infrared Spectroscopy, Powder X-ray Diffraction, Thermogravimetric Analysis, Scanning Electron Microscope and Transmission Electron Microscopy.

Efficiency of zero-dimensional and two-dimensional graphene architectural nanocomposites for organic transformations in the contemporary environment: a review

Graphene derivatives-based nanocatalyst finds increasing utilisation in the catalysis field for organic transformations. Researchers have been working on the development of graphene oxide, reduced graphene oxide, and graphene quantum dots with metal or metal oxide nanocomposites over the last few years. These materials exhibit excellent electrical, catalytic, optical, thermal, and magnetic properties. In particular, GO/rGO/GQDs composites assisted by metal or metal oxides have attracted broad attention for their possible applications in organic compound synthesis, drug delivery, sensors, devices, and the related areas of the environment. In this review, we have summarised GO/rGO/GQDs-metal or metal oxide composites using catalyst for organic conversions and synthesis of organic compounds in accordance with the discussion on the key problems and prospects for future study. Furthermore, there is a significant function for the catalytic efficiency of composites assisted by metal or metal oxide nanocatalyst which is categorised by graphene derivatives bases.

Cu12@Au30Ag12: a magnetic pentakis icosidodecahedron molecule with core-shell configuration

A 54-atom trimetallic core-shell Cu₁₂@Au₃₀Ag₁₂ molecule has been identified by using first-principles calculations. This molecule with I_h symmetry consists of an icosahedral 12-atom Cu core (Cu₁₂) coated by a pentakis icosidodecahedral 42-atom Au-Ag shell (Au₃₀Ag₁₂) composed of an icosidodecahedral Au₃₀ and an icosahedral Ag₁₂. Both the molecular dynamics simulations and vibrational frequency analysis demonstrate the high stability of Cu₁₂@Au₃₀Ag₁₂. The analyses for electronic properties indicate that there exists spd hybridization which is crucial to maintain the geometrical configuration of Cu₁₂@Au₃₀Ag₁₂. Moreover, a total spin magnetic moment of Cu₁₂@Au₃₀Ag₁₂ is found to be 4 µ_B, which chiefly arises from the 6 s states of Au atoms. A new type of sugar gourd-like [Cu₁₂@Au₃₀Ag₁₁]_n nanowire is also proposed; the results demonstrate that the nanowire exhibits metallic and magnetic behaviors. The magnetic Cu₁₂@Au₃₀Ag₁₂ molecule and [Cu₁₂@Au₃₀Ag₁₁]_n nanowire can be promising candidates of novel magnetic nanomaterials and nanodevices.

Preparation of cost-effective Ni-Ag bimetallic catalyst for hydrodehalogenation of aryl halides under mild conditions

Cost-effective Ni-Ag bimetallic nanoparticles were prepared using an aqueous-phase surfactant-aided co-reduction process and used as catalyst for the hydrodehalogenation of aryl halides CAr-X (X=F, Cl, Br). The CAr-X could be...

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

Bio-DEE Synthesis and Dehydrogenation Coupling of Bio-Ethanol to Bio-Butanol over Multicomponent Mixed Metal Oxide Catalysts

Within the Waste2Fuel project, innovative, high-performance, and cost-effective fuel production methods from municipal solid wastes (MSWs) are sought for application as energy carriers or direct drop-in fuels/chemicals in the near-future low-carbon power generation systems and internal combustion engines. Among the studied energy vectors, C1-C2 alcohols and ethers are mainly addressed. This study presents a potential bio-derived ethanol oxidative coupling in the gas phase in multicomponent systems derived from hydrotalcite-containing precursors. The reaction of alcohol coupling to ethers has great importance due to their uses in different fields. The samples have been synthesized by the co-precipitation method via layered double hydroxide (LDH) material synthesis, with a controlled pH, where the M(II)/M(III) ≈ 0.35. The chemical composition and topology of the sample surface play essential roles in catalyst activity and product distribution. The multiple redox couples Ni2+/Ni3+, Cr2+/Cr3+, Mn2+/Mn3+, and the oxygen-vacant sites were considered as the main active sites. The introduction of Cr (Cr3+/Cr4+) and Mn (Mn3+/Mn4+) into the crystal lattice could enhance the number of oxygen vacancies and affect the acid/base properties of derived mixed oxides, which are considered as crucial parameters for process selectivity towards bio-DEE and bio-butanol, preventing long CH chain formation and coke deposition at the same time.

Bimetallic nanocatalysts supported on graphitic carbon nitride for sustainable energy development: the shape-structure-activity relation

The catalytic performance of metal nanoparticles (NPs), including activity, selectivity, and durability, depends on their shape and structure at the molecular level. Consequently, metal NPs of different size and shape, e.g., nanobelts, nanocubes, nanoflakes, and nanowires, demonstrate different reactivity and provide different reaction rates depending on the facet exposed. In this context, the present review aims to summarize the shape-structure-activity relation of metallic nanocatalysts. Moreover, keeping in mind that the application of noble metal catalysts is expensive, we would like to draw the reader's attention to bimetallic nanocatalysts supported on graphitic carbon nitride. One of the advantages of these systems is the possibility to minimize the use of noble metals by introducing another metal either to the parent NPs and/or modifying the support materials. The development and optimization of bimetallic nanocatalysts might provide the new class of materials with superior, tunable performance, thermal stability and reduced costs compared to presently available commercial catalysts. Therefore, further application of these bimetallic composites for sustainable development in energy, green chemicals/fuels and environmental protection will be discussed.

Pd@Pt-GOx/HA as a Novel Enzymatic Cascade Nanoreactor for High-Efficiency Starving-Enhanced Chemodynamic Cancer Therapy

Glucose oxidase (GOx)-mediated starvation therapy has demonstrated good application prospect in cancer treatment. However, the glucose- and oxygen-depletion starvation therapy still suffers from some limitations like low therapeutic efficiency and potential side effects to normal tissues. To overcome these disadvantages, herein a novel enzymatic cascade nanoreactor (Pd@Pt-GOx/hyaluronic acid (HA)) with controllable enzymatic activities was developed for high-efficiency starving-enhanced chemodynamic cancer therapy. The Pd@Pt-GOx/HA was fabricated by covalent conjugation of GOx onto Pd@Pt nanosheets (NSs), followed by linkage with hyaluronic acid (HA). The modification of HA on Pd@Pt-GOx could block the GOx activity, catalase (CAT)-like and peroxidase (POD)-like activities of Pd@Pt, reduce the cytotoxicity to normal cells and organs, and effectively target CD44-overexpressed tumors by active targeting and passive enhanced permeability and retention (EPR) effect. After endocytosis by tumor cells, the intracellular hyaluronidase (Hyase) could decompose the outer HA and expose Pd@Pt-GOx for the enzymatic cascade reaction. The GOx on the Pd@Pt-GOx could catalyze the oxidation of intratumoral glucose by O₂ for cancer starvation therapy, while the O₂ produced from the decomposition of endogenous H₂O₂ by the Pd@Pt with the CAT-like activity could accelerate the O₂-dependent depletion of glucose by GOx. Meanwhile, the upregulated acidity and H₂O₂ content in the tumor region generated by GOx catalytic oxidation of glucose dramatically facilitated the pH-responsive POD-like activity of the Pd@Pt nanozyme, which then catalyzed degradation of the H₂O₂ to generate abundant highly toxic ^•OH, thereby realizing nanozyme-mediated starving-enhanced chemodynamic cancer therapy. In vitro and in vivo results indicated that the controllable, self-activated enzymatic cascade nanoreactors exerted highly efficient anticancer effects with negligible biotoxicity.

A Review of Microwave-Assisted Synthesis-Based Approaches to Reduce Pd-Content in Catalysts

This review article focuses on the latest advances in the synthesis of inorganic nano-catalysts using microwave heating, which has progressed significantly since its initial implementation in the mid-1980s. Over the years, nanoparticles (NPs), which inherently offer better surface accessibility for heterogeneous catalysis, have been synthesized using a wide array of heating methods. Microwave heating is one such method and employs a unique heating mechanism that can have several benefits for catalysis. When compared to conventional form of heating which relies on inter-layer mixing via convection, microwave heating operates through the chemical polarity in the target chemicals leading to an “inside-out” mode of heating. This heating mechanism is more targeted and therefore results in rapid synthesis of catalytically active NPs. Platinum group metals (PGM) have classically been the focus of nano-catalysis; however, recent efforts have also applied non-PGM group metals with the goals of lower costs, and ideally, improved catalytic reactivity and durability. This is especially of interest with respect to Pd because of its current historically high cost. Investigations into these new materials have primarily focused on new/improved synthetic methods and catalytic compositions, but it is important to note that these approaches must also be economic and scalable to attain practical relevance. With this overarching goal in mind, this review summarizes notable recent findings with a focus on Pd-dilution and microwave heating in a chronological fashion.

Titania nanotubes coated with graphene as a promising catalyst for the oxygen reduction reaction

The enhanced electrocatalytic properties of rGO/TiO₂NTs for the ORR are a result of increased specific surface area, number of active sites and accelerated electron conductivity.

One-pot, chemoselective synthesis of secondary amines from aryl nitriles using a PdPt–Fe3O4 nanoparticle catalyst

We have developed a new catalytic method for the one-pot, cascade synthesis of unsymmetrical secondary amines via the reductive amination of aryl nitriles with nitroalkanes using a PdPt–Fe₃O₄ nanoparticle (NP) catalyst.

Recent Progress in Graphene-Based Noble-Metal Nanocomposites for Electrocatalytic Applications

The fast industrialization process has led to global challenges in the energy crisis and environmental pollution, which might be solved with clean and renewable energy. Highly efficient electrochemical systems for clean-energy collection require high-performance electrocatalysts, including Au, Pt, Pd, Ru, etc. Graphene, a single-layer 2D carbon nanosheet, possesses many intriguing properties, and has attracted tremendous research attention. Specifically, graphene and graphene derivatives have been utilized as templates for the synthesis of various noble-metal nanocomposites, showing excellent performance in electrocatalytic-energy-conversion applications, such as the hydrogen evolution reaction and CO₂ reduction. Herein, the recent progress in graphene-based noble-metal nanocomposites is summarized, focusing on their synthetic methods and electrocatalytic applications. Furthermore, some personal insights on the challenges and possible future work in this research field are proposed.

Copper oxide-graphene oxide nanocomposite: efficient catalyst for hydrogenation of nitroaromatics in water

A low-cost nanocomposite catalyst containing copper oxide (CuO) nanoparticles (NPs) on graphene oxide (GO) was fabricated by a facile hydrothermal self-assembly process. The segregated CuO NPs and GO exhibited negligible catalytic activities for the reduction of nitroaromatics. However, their hybrid composite accomplished facile reduction with high conversions for several substituted nitroaromatics in aqueous NaBH4 solution; synergetic coupling effect of CuO NPs with GO in the nanocomposite catalyst provided excellent catalytic activity. The nanocomposite catalyst could be separated from the reaction mixture and recycled consecutively.

Recent Advances in the Nanocatalysts-assisted NaBH4 Reduction of Nitroaromatics in water

In view of the increasing applications of nanocatalysis in chemical transformations, this article illustrates recent advances on the use of nanocatalysts for an important reduction reaction, the hydrogenation of nitroaromatics to significant aminoaromatics with aqueous NaBH₄ solution; the utility of mono- and multi-metal nanocatalysts with special emphasis on heterogeneous nanocatalysts are included. A progressive trend on the applicability of nanocatalysts is also incorporated with large scale application and their sustainable recyclization and reuse utilizing supported and magnetic nanocatalysts; representative methods for the synthesis of such reusable nanocatalysts are featured.

Pd nanoparticles on green support as dip-catalyst: a facile transfer hydrogenation of olefins and N-heteroarenes in water

Chemo- and regioselective hydrogenation methods using highly green sources, particularly from metal nanoparticles on plant stem as support and water, is an intensive research area, which is highly relevant to the development of green chemistry and technology in the 21^st century. Here, the synthesis and activity of a heterogeneous catalytic system (called “dip-catalyst”) for the transfer hydrogenation of a series of styrenyl, unfunctionalized olefins, quinoline and other N-heteroarenes, are presented. It consists of Pd nanoparticles (15–20 nm) anchored on bio-processed jute plant (Corchorus genus) stem as the support. Pd nanoparticles were decorated on the green support (GS) jute stem by the in situ reduction of K₂PdCl₄ in aqueous medium at 70 °C, using formic acid as the reductant. The Pd@GS was characterized using SEM, EDS, XRD, FTIR, XPS and TEM. Elemental mapping revealed uniform distribution of Pd on the cellulose matrix of the jute stem. The catalyst was successfully applied to the chemoselective transfer hydrogenation of numerous styrenyl, unfunctionalized olefins. Its high functional group tolerance was investigated during the olefins hydrogenation in water. Furthermore, Pd@GS was capable of quantitative hydrogenation to selectively produce 1,2,3,4-tetrahydroquinoline (THQ) in water using stoichiometric amounts of tetrahydroxydiboron (THDB) at 60 °C with turn over frequency (TOF) 4938 h⁻¹. This system is stable in water and displays excellent recyclability; it could be used for 32 consecutive cycles, without losing its original crystallinity or requiring replenishment.

A dip catalyst consisting of Pd nanoparticles immobilized on the surface of thin slices of jute-stem was fabricated. Its versatility as a hydrogen transfer agent for styrenyl, cyclic and unfunctionalized olefins and N-heterocycles was investigated.

A capping agent dissolution method for the synthesis of metal nanosponges and their catalytic activity towards nitroarene reduction under mild conditions

We report a general strategy for the synthesis of metal nanosponges (M = Ag, Au, Pt, Pd, and Cu) using a capping agent dissolution method where addition of water to the M@BNHx nanocomposite affords the metal nanosponges. The B-H bond of the BNHx polymer gets hydrolysed upon addition of water and produces hydrogen gas bubbles which act as dynamic templates leading to the formation of nanosponges. The rate of B-H bond hydrolysis has a direct impact on the final nanostructure of the materials. The metal nanosponges were characterized using powder XRD, electron microscopy, XPS, and BET surface area analyzer techniques. The porous structure of these nanosponges offers a large number of accessible surface sites for catalytic reactions. The catalytic activity of these metal nanosponges has been demonstrated for the reduction of 4-nitrophenol where palladium exhibits the highest catalytic activity (k = 0.314 min-1). The catalytic activity of palladium nanosponge was verified for the tandem dehydrogenation of ammonia borane and the hydrogenation of nitroarenes to arylamines in methanol at room temperature. The reduction of various substituted nitroarenes was proven to be functional group tolerant except for a few halogenated nitroarenes (X = Br and I) and >99% conversion was noted within 30-60 min with high turnover frequencies (TOF) at low catalyst loading (0.1 mol%). The catalyst could be easily separated out from the reaction mixture via centrifugation and was recyclable over several cycles, retaining its porous structure.

Sustainable superior function of the synthesized NixCo1-xFe2Oz nanosphere on the destruction of chlorinated biphenyls in the effluent

Ni_xCo_1-xFe₂O_z composite oxide nanosphere was successfully prepared, to degrade 2-monochlorobiphenly (CB-1) in continuous-flow fixed-bed microreactor at GHSV of 20000h^-1. The five cycles of temperature-dependent run experiments between 150 and 350°C showed its superior activity with a CB-1 conversion of more than 95% above 300°C over Ni_0.5Co_0.5Fe₂O_z. Importantly, the sustainable higher reactivity could be observed over prolonged 600min reaction times after the 5th run test. The degradation products detected as biphenyl and monochlorobenzene with yield ratio of 129, account for 0.24% and 0.0011% of initial CB-1 respectively. This indicated the weak occurrence of hydrodechlorination and breakage of CC bridge bond during the degradation of CB-1. The possibly dominant occurrence of oxidative degradation probably follows Mars-van Krevelen mechanism, resulting in the generation of the formic, acetic, propanoic and butyric acids and so on. Due to the high oxygen mobility over Ni_0.5Co_0.5Fe₂O_z nanosphere, the consumed oxygen species could be compensated rapidly by the gas phase oxygen via O₂→O₂^- → 2O^- → 2O^2-. The interaction among different elements in Ni_0.5Co_0.5Fe₂O_z nanosphere confirmed by the derivation of the electron cloud, enhanced the mobility of the reactive oxygen species, which would be beneficial for the oxidation of chlorinated biphenyls.

Synthesis of TiO2/rGO composites with different morphologies and their electrocatalysis for the oxygen reduction reaction

An octahedral TiO₂/rGO composite shows the best catalytic activity for the ORR.