Eruption combustion synthesis of NiO/Ni nanocomposites with enhanced properties for dye-absorption and lithium storage

Simultaneous removal of organic and inorganic pollutants from water by Ni/NiO/SnO2 nanoparticles

Herein, we report a facile synthesis of Ni/NiO/SnO₂ hybrids where the core-shell-type Ni/NiO nanoparticle is decorated with the SnO₂ nanoparticle to make a heterojunction and their potential evaluation for simultaneous removal of organic and inorganic pollutants. The metallic nickel core of the nanoparticle helps to separate easily from water magnetically and restricts the possible secondary contamination. The formation of semiconductor-semiconductor heterojunction enhances the photocatalytic activity to degrade the organic pollutants. The nanomaterial was characterized using microscopic, spectroscopic, and BET analyses. Results indicated an efficient degradation of ~ 94% of crystal violet in 40 min. An adsorption capacity of ~ 530 mg g^-1 and ~ 650 mg g^-1 of cadmium and lead ions, respectively, was found for single-component adsorption experiments, and ~ 520 mg g^-1 and ~ 720 mg g^-1 of cadmium and lead ions, respectively, were found for multi-component experiments. This observation suggested that the lead and cadmium ion adsorption process is affected by the synergistic and antagonistic effects, respectively. However, no significant change in the photocatalytic activity was observed for multi-component experiments. Results indicated that the process followed the Langmuir isotherm and pseudo-second-order kinetics irrespective of the number of pollutants present. An excellent adsorption capacity of metal ions and photodegradation capability of organic dye in multi-component solution, and possible reusability of the nanoparticle, make the Ni/NiO/SnO₂ a potential material for simultaneous removal of organic and inorganic pollutants.

A novel N,S-rich COF and its derived hollow N,S-doped carbon@Pd nanorods for electrochemical detection of Hg2+ and paracetamol

Covalent-organic frameworks (COFs) are conjugate crystalline polymers with high porosity, controllable pores and structure as well as large specific surface area, showing great potential for electrochemical sensors. Here, a new N,S-rich COF_BTT-TZT is proposed by direct amine-aldehyde dehydration condensation between 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TZT) and benzo [1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde (BTT). The COF_BTT-TZT has a hexagonal hcb structure with theoretical pore of 2.2 nm and presents rod-like morphology with many small flakes on its surface. Particularly, there are lots of S and N atoms in COF_BTT-TZT, which provides abundant adsorption sites for Hg²⁺ so that it can be used to detect Hg²⁺. The proposed Hg²⁺ sensor has a linear range of 0.54 nM-5.0 μM and a detection limit of 0.18 nM. Besides, using COF_BTT-TZT as precursor and template, the hollow N,S-doped C@Pd nanorods which possesses many tiny Pd nanoparticles embedded in rods-like hollow structure are obtained. An electrochemical paracetamol sensor is also proposed based on the N,S-doped C@Pd nanorods, showing low detection limit of 11 nM and wide linear range of 33 nM-120 μM. The good results provide an important guidance for the application of COF in electrochemical sensors.

Catalytic activity of porous manganese oxides for benzene oxidation improved via citric acid solution combustion synthesis

Various manganese oxides (MnO_x) prepared via citric acid solution combustion synthesis were applied for catalytic oxidation of benzene. The results showed the ratios of citric acid/manganese nitrate in synthesizing process positively affected the physicochemical properties of MnO_x, e.g., BET (Brunauer-Emmett-Teller) surface area, porous structure, reducibility and so on, which were in close relationship with their catalytic performance. Of all the catalysts, the sample prepared at a citric acid/manganese nitrate ratio of 2:1 (C2M1) displayed the best catalytic activity with T₉₀ (the temperature when 90% of benzene was catalytically oxidized) of 212℃. Further investigation showed that C2M1 was Mn₂O₃ with abundant nano-pores, the largest surface area and the proper ratio of surface Mn⁴⁺/Mn³⁺, resulting in preferable low-temperature reducibility and abundant surface active adsorbed oxygen species. The analysis results of the in-situ Fourier transform infrared spectroscopy (in-situ FTIR) revealed that the benzene was successively oxidized to phenolate, o-benzoquinone, small molecules (such as maleates, acetates, and vinyl), and finally transformed to CO₂ and H₂O.

A highly active Ni-based anode material for urea electrocatalysis by a modified sol-gel method

A highly electroactive Ni-based catalyst for urea oxidation is prepared by a sol-gel method with bubbling of gel mixture. It is observed that the conditions for the gel formation strongly affect the morphology and electrochemical properties of the catalyst materials. As synthesized Ni-catalysts are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The Ni-based catalyst prepared at optimum conditions in the scope of this study exhibits the urea oxidation activity of 570 mA mg^-1 (at 0.54 V). In a single urea/hydrogen peroxide fuel cell test, the Ni-catalyst provides maximum power densities of 19.6 and 36.4 mW cm^-2 at 30 and 70 °C, respectively. Additionally, the cell catalyst shows a stable voltage for 3 days. Thus, this work suggests that a novel Ni-based catalyst derived from a facile method can be used for urea oxidation and as an efficient anode material for urea fuel cells.

Sucrose-Triggered, Self-Sustained Combustive Synthesis of Magnetic Nickel Oxide Nanoparticles and Efficient Removal of Malachite Green from Water

Dye-containing industrial effluents create major concern nowadays. To address the problem, magnetic nickel oxide nanoparticles (NONPs) were synthesized using the autopropagator combustion technique assisted by sucrose as fuel and used for the removal of toxic malachite green (MG) from water. The material was characterized by scanning electron microscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating sample magnetism (VSM), point of zero charge (pH_ZPC), and Brunauer-Emmet-Teller surface area analysis. SEM images show flowerlike texture with the presence of multiple pores. VSM reveals a well-defined hysteresis at room temperature, confirming a permanent magnetic nature of the material. pH_ZPC was found to be 6.63, which enables dye separation in the drinking water pH range. MG removal from water was carried out in the batch mode with optimized physicochemical parameters such as contact time, pH, temperature, and dose. Langmuir adsorption capacity was estimated to be 87.72 mg/g. Pseudo-second order kinetics (R ² = 0.999) and Langmuir isotherm model (R ² = 0.997) were found to best fit. The magnetic nature facilitates fast and quantitative separation of NONPs from solution using a hand-held magnet. Dye-loaded NONPs can be easily regenerated up to 89% and reused up to five cycles without significant loss of activity. The mechanism of adsorption is proposed to be a combination of electrostatic attraction and weak hydrogen bonding. Strategically designed straightforward synthetic protocol, low cost, high uptake capacity, and sustainable use render NONPs an ideal alternative for future dye treatment.

Oxalate-derived porous prismatic nickel/nickel oxide nanocomposites toward lithium-ion battery

NiO is a highly appealing anode material for lithium-ion batteries (LIBs) owing to its relatively high Li storage capacity. However, its low electrical conductivity and large volume change during the battery cycling process limit its application. Here, we fabricate a series of porous Ni/NiO (M) nanocomposites through the direct pyrolysis of a nickel oxalate precursor and adjust the Ni(0) content by varying the pyrolysis temperature. The porous architecture is beneficial for alleviating the volume expansion/constriction during cycling. The Ni in the composites accelerates the electrochemical reaction kinetics and enhances the conductivity of the electrode materials. The M-2 electrode with a 17.9% Ni(0) content realizes a high reversible capacity (633.7 mA h g^-1 after 100 cycles at 0.2 A g^-1) and exhibits outstanding rate capability (307.6 mA h g^-1 after 250 cycles at 1 A g^-1). This work can not only supply an approach to adjust the content of an element with specific valence state, but also provide an inspiration for the fabrication of porous metal/metal oxide anode materials in LIBs.

Polypropylene Nonwoven Fabric@Poly(ionic liquid)s for Switchable Oil/Water Separation, Dye Absorption, and Antibacterial Applications

Pollutants in wastewater include oils, dyes, and bacteria, making wastewater cleanup difficult. Multifunctional wastewater treatment media consisting of poly(ionic liquid)-grafted polypropylene (PP) nonwoven fabrics (PP@PIL) are prepared by a simple and scalable surface-grafting process. The fabricated PP@PIL fabrics exhibit impressive switchable oil/water separation (η>99 %) and dye absorption performance (q=410 mg g^-1 ), as well as high antibacterial properties. The oil/water separation can be easily switched by anion exchanging of the PIL segments. Moreover, the multiple functions (oil/water separation, dye absorption, and antibacterial properties) occurred at the same time, and did not interfere with each other. The multifunctional fibrous filter can be easily regenerated by washing with an acid solution, and the absorption capacity is maintained after many recycling tests. These promising features make PIL-grafted PP nonwoven fabric a potential one-step treatment for multicomponent wastewater.

Performance of Solid-state Hybrid Energy-storage Device using Reduced Graphene-oxide Anchored Sol-gel Derived Ni/NiO Nanocomposite

The influence of (nickel nitrate/citric acid) mole ratio on the formation of sol-gel end products was examined. The formed Ni/NiO nanoparticle was anchored on to reduced graphene-oxide (rGO) by means of probe sonication. It was found that the sample obtained from the (1:1) nickel ion: citric acid (Ni²⁺: CA) mole ratio resulted in a high specific capacity of 158 C/g among all (Ni²⁺: CA) ratios examined. By anchoring Ni/NiO on to the rGO resulted in enhanced specific capacity of as high as 335 C/g along with improved cycling stability, high rate capability and Coulombic efficiency. The high conductivity and increased surface area seemed responsible for enhanced electrochemical performances of the Ni/NiO@rGO nanocomposite. A solid-state hybrid energy-storage device consisting of the Ni/NiO@rGO (NR₂) as a positive electrode and the rGO as negative electrode exhibited enhanced energy and power densities. Lighting of LED was demonstrated by using three proto-type (NR₂⁽⁺⁾|| rGO⁽⁻⁾) hybrid devices connected in series.

High-rate-capability asymmetric supercapacitor device based on lily-like Co3O4 nanostructures assembled using nanowires

In this paper, high-rate-capability asymmetric supercapacitor device assembled by lily-like Co₃O₄ nanostructures and active carbon was presented.

Solution Combustion Synthesis of Nanoscale Materials

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol-gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual properties are outlined. To demonstrate the versatility of the approach, several application categories of SCS produced materials, such as for energy conversion and storage, optical devices, catalysts, and various important nanoceramics (e.g., bio-, electro-, magnetic), are discussed.

Structure Interlacing and Pore Engineering of Zn2GeO4 Nanofibers for Achieving High Capacity and Rate Capability as an Anode Material of Lithium Ion Batteries

An interlaced Zn2GeO4 nanofiber network with continuous and interpenetrated mesoporous structure was prepared using a facile electrospinning method followed by a thermal treatment. The mesoporous structure in Zn2GeO4 nanofibers is directly in situ constructed by the decomposition of polyvinylpyrolidone (PVP), while the interlaced nanofiber network is achieved by the mutual fusion of the junctions between nanofibers in higher calcination temperatures. When used as an anode material in lithium ion batteries (LIBs), it exhibits superior lithium storage performance in terms of specific capacity, cycling stability, and rate capability. The pore engineering and the interlaced network structure are believed to be responsible for the excellent lithium storage performance. The pore structure allows for easy diffusion of electrolyte, shortens the pathway of Li(+) transport, and alleviates large volume variation during repeated Li(+) extraction/insertion. Moreover, the interlaced network structure can provide continuous electron/ion pathways and effectively accommodate the strain induced by the volume change during the electrochemical reaction, thus maintaining structural stability and mechanical integrity of electrode materials during lithiation/delithiation process. This strategy in current work offers a new perspective in designing high-performance electrodes for LIBs.

Solution combustion synthesis of nanosized WOx: characterization, mechanism and excellent photocatalytic properties

We present a method called solution combustion synthesis by using metal acid radical ions to design nanostructured tungsten oxide with both stoichiometric and oxygen-vacancy-rich nonstoichiometric oxides with excellent photocatalytic activity.

Solution combustion synthesis of metal oxide nanomaterials for energy storage and conversion

The design and synthesis of metal oxide nanomaterials is one of the key steps for achieving highly efficient energy conversion and storage on an industrial scale. Solution combustion synthesis (SCS) is a time- and energy-saving method as compared with other routes, especially for the preparation of complex oxides which can be easily adapted for scale-up applications. This review summarizes the synthesis of various metal oxide nanomaterials and their applications for energy conversion and storage, including lithium-ion batteries, supercapacitors, hydrogen and methane production, fuel cells and solar cells. In particular, some novel concepts such as reverse support combustion, self-combustion of ionic liquids, and creation of oxygen vacancies are presented. SCS has some unique advantages such as its capability for in situ doping of oxides and construction of heterojunctions. The well-developed porosity and large specific surface area caused by gas evolution during the combustion process endow the resulting materials with exceptional properties. The relationship between the structural properties of the metal oxides studied and their performance is discussed. Finally, the conclusions and perspectives are briefly presented.

Carbon-Anchored MnO Nanosheets as an Anode for High-Rate and Long-Life Lithium-Ion Batteries

Developing electrode materials with high rate as well as prolonged cycle is particularly necessary for the ever-growing market penetration of electric vehicles and hybrid electric vehicle. Herein, we demonstrate a facile and efficient strategy to synthesize MnO/C hybrid via freeze-drying followed by thermal treatment in N2 atmosphere. The MnO nanosheets are firmly anchored onto carbon layers to form MnO/C hybrid. When used as an anode in lithium-ion batteries, the typical MnO/C hybrid displays a high initial Coulombic efficiency of 83.1% and delivers a high capacity of 1449.8 mAh g(-1) after 100 cycles at 0.3 A g(-1). Furthermore, the typical MnO/C hybrid can still maintain significantly high capacity of 1467.0 mAh g(-1) after 2000 cycles at 5 A g(-1), which may be the best performance reported so far for MnO-based materials. The superior electrochemical performance of the MnO/C hybrid may be attributed to its unique microstructure features such as effective conductive pathway of carbon sheets, firm connection between MnO and carbon sheets, and small-sized MnO.

Combustion synthesis and excellent photocatalytic degradation properties of W18O49

One-dimensional W₁₈O₄₉ nanoneedles were fabricated by solution combustion synthesis and exhibited an excellent visible light-driven photocatalytic performance.

An efficient three-component synthesis of coumarin-3-carbamides by use of Ni–NiO nanoparticles as magnetically separable catalyst

An efficient and ecofriendly synthesis of coumarin-3-carbamides has been developed by a three-component reaction of 2-hydroxybenzaldehydes, aliphatic amines (p-/s-) and diethyl malonate using Ni–NiO nanoparticles as catalyst.

Nanomaterials via solution combustion synthesis: a step nearer to controllability

Recent progress in phase- and morphology-controlled solution combustion synthesis envisages mass fabrications of nanomaterials with more specified phases and morphologies.

Encapsulation of metal oxide nanocrystals into porous carbon with ultrahigh performances in lithium-ion battery

A simple and industrial scalable approach was developed to encapsulate metal oxide nanocrystals into porous carbon (PC) with a high distribution. With this method, the composite of PC-metal oxide were prepared in a large amount with a low cost; particularly they exhibit ultrahigh performances in lithium-ion battery applications. For example, the PC-CoOx and PC-FeOx show a high capacity around 1021 mA h g(-1) and 1200 mA h g(-1) at the current density of 100 mA g(-1) respectively, together with an excellent cycling ability (>400 cycles) and rate capacity even at the high current densities of 3 A g(-1) and 5 A g(-1).