There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Metal-organic framework (MOF) nanoparticles, also called porous coordination polymers, are a major part of nanomaterials science, and their role in catalysis is becoming central. The extraordinary variability and richness of their structures afford engineering synergies between the metal nodes, functional linkers, encapsulated substrates, or nanoparticles for multiple and selective heterogeneous interactions and activations in these MOF-based nanocatalysts. Pyrolysis of MOF-nanoparticle composites forms highly porous N- or P-doped graphitized MOF-derived nanomaterials that are increasingly used as efficient catalysts especially in electro- and photocatalysis. This review first briefly summarizes this background of MOF nanoparticle catalysis and then comprehensively reviews the fast-growing literature reported during the last years. The major parts are catalysis of organic and molecular reactions, electrocatalysis, photocatalysis, and views of prospects. Major challenges of our society are addressed using these well-defined heterogeneous catalysts in the fields of synthesis, energy, and environment. In spite of the many achievements, enormous progress is still necessary to improve our understanding of the processes involved beyond the proof-of-concept, particularly for selective methane oxidation, hydrogen production, water splitting, CO2 reduction to methanol, nitrogen fixation, and water depollution.

State of the Art and Prospects in Metal-Organic Framework (MOF)-Based and MOF-Derived Nanocatalysis.

Oil sorbents play a very important part in the remediation processes of oil spills. To enhance the oil-sorption properties and simplify the oil-recovery process, various advanced oil sorbents and oil-collecting devices based on them have been proposed recently. Here, we firstly discuss the design considerations for the fabrication of oil sorbents and describe recently developed oil sorbents based on modification strategy. Then, recent advances regarding oil sorbents mainly based on carbon materials and swellable oleophilic polymers are also presented. Subsequently, some additional properties are emphasized, which are required by oil sorbents to cope with oil spills under extreme conditions or to facilitate the oil-collection processes. Furthermore, some oil-collection devices based on oil sorbents that have been developed recently are shown. Finally, an outlook and challenges for the next generation of oil-spill-remediation technology based on oil-sorbents materials are given.

Advanced Sorbents for Oil-Spill Cleanup: Recent Advances and Future Perspectives

The reduction of nitro compounds to the corresponding amines is one of the most utilized catalytic processes in the fine and bulk chemical industry. The latest development of catalysts with cheap metals like Fe, Co, Ni, and Cu has led to their tremendous achievements over the last years prompting their greater application as “standard” catalysts. In this review, we will comprehensively discuss the use of homogeneous and heterogeneous catalysts based on non-noble 3d-metals for the reduction of nitro compounds using various reductants. The different systems will be revised considering both the catalytic performances and synthetic aspects highlighting also their advantages and disadvantages.

/pdf/reduction-of-nitro-compounds-using-3d-non-noble-metal-5b70ogvyef.pdf

Reduction of Nitro Compounds Using 3d-Non-Noble Metal Catalysts

Nitroarene reduction: a trusted model reaction to test nanoparticle catalysts

Superhydrophobic surfaces prevent percolation of water droplets and thus render roll-off, self-cleaning, corrosion protection, etc., which find day-to-day and industrial applications. In this work, we developed a facile, cost-effective, and free-standing method for direct fabrication of copper nanoparticles to engender superhydrophobicity for various flat and irregular surfaces such as glass, transparency sheet (plastic), cotton wool, textile, and silicon substrates. The fabrication of as-prepared superhydrophobic surfaces was accomplished using a simple chemical reduction of copper acetate by hydrazine hydrate at room temperature. The surface morphological studies demonstrate that the as-prepared surfaces are rough and display superhydrophobic character on wetting due to generation of air pockets (The Cassie-Baxter state). Because of the low adhesion of water droplets on the as-prepared surfaces, the surfaces exhibited not only high water contact angle (164 ± 2°, 5 μL droplets) but also superb roll-off and self-cleaning properties. Superhydrophobic copper nanoparticle coated glass surface uniquely withstands water (10 min), mild alkali (5 min in saturated aqueous NaHCO3 of pH ≈ 9), acids (10 s in dilute HNO3, H2SO4 of pH ≈ 5) and thiol (10 s in neat 1-octanethiol) at room temperature (25-35 °C). Again as-prepared surface (cotton wool) was also found to be very effective for water-kerosene separation due to its superhydrophobic and oleophilic character. Additionally, the superhydrophobic copper nanoparticle (deposited on glass surface) was found to exhibit antibacterial activity against both Gram-negative and Gram-positive bacteria.

Fabrication of superhydrophobic copper surface on various substrates for roll-off, self-cleaning, and water/oil separation.

In this work, we have disclosed the facile syntheses of morphologically diverse Cu2O nanoparticles using our laboratory designed modified hydrothermal reactor employing low-cost copper (II) acetate precursor compounds. The reaction conditions dovetail the effect of ethylene glycol (EG) and glucose to exclusively evolve the morphology tuned Cu2O nanomaterial at different pHs. The morphology tuning produces octahedron (Oh), dwarf hexapod (DHP), and elongated hexapod (EHP) Cu2O structures only with the optimized reagent concentrations. Interestingly, all of them were bestowed with a (111) facet, a superlative facet for facile nitroarene reduction. Thus, the morphology reliant catalytic reaction becomes evident. However, when used individually, EG and glucose evolve ill-defined CuO/Cu2O and Cu2O structures, respectively. We have observed that a change in pH of the medium at the onset of the reaction is obligatory for the evolution of tailor-made morphologically diverse Cu2O nanoparticles. However, preformed C...

Remarkable Facet Selective Reduction of 4-Nitrophenol by Morphologically Tailored (111) Faceted Cu2O Nanocatalyst

Liquor ammonia mediated V(V) insertion in thin Co3O4 sheets for improved pseudocapacitors with high energy density and high specific capacitance value

Modified hydrothermal route (MHT)-evolved Mn3O4 nanoparticles of ∼60 nm diameter were anchored onto a conductive multiwalled carbon nanotubes (MWCNTs) backbone (again under MHT) to produce an energy storage composite. To obtain the benefits of a low cost and stable MWCNT/Mn3O4 composite as a supercapacitor, cyclic voltammetry (CV) and galvanostatic charge–discharge measurements (GCD), as well as cycling stability and electrochemical impedance studies (EIS) have been performed. The electrochemical measurements reveal the suitability of the as-synthesized MWCNT/Mn3O4 composite as an electrode material with a highest specific capacitance of 441 F g−1 at 2 mV s−1 scan rate, which is 1.4 times higher than the specific capacitance (312 F g−1 at a scan rate of 2 mV s−1) of the bare Mn3O4 nanoparticle. MWCNT/Mn3O4 shows an excellent rate capability, outstanding long-term cyclic stability (98% capacity retention after 1000 consecutive cycles) and better power density and energy density. Due to the synergistic effect operating between the pseudocapacitor Mn3O4 nanoparticle and the conductive MWCNT, the capacitive performance of the composite electrode was considerably improved, and we perceive that the composite effect could have benefit in terms of supercapacitor application. These interesting improved material properties of the as-synthesized material indicate that the material is a suitable candidate for use in future energy storage applications.

Teresa Aditya

Papers

Nitroarene reduction: a trusted model reaction to test nanoparticle catalysts

Fabrication of superhydrophobic copper surface on various substrates for roll-off, self-cleaning, and water/oil separation.

Remarkable Facet Selective Reduction of 4-Nitrophenol by Morphologically Tailored (111) Faceted Cu2O Nanocatalyst

Liquor ammonia mediated V(V) insertion in thin Co3O4 sheets for improved pseudocapacitors with high energy density and high specific capacitance value

Mn3O4 nanoparticles anchored to multiwall carbon nanotubes: a distinctive synergism for high-performance supercapacitors