Assistance Of Urea Research Articles

Recycling of Li and Co from spent LiCoO2 cathode materials through a low-temperature urea-assisted sulfation roasting approach

With the assistance of urea, ammonium sulfate roasting can be carried out more efficiently to convert spent LiCoO2 battery cathode materials into water-leachable substances for recycling.

Novel Nitrogen‐Doped Porous Carbon with High Surface Areas Prepared from Industrial Alkali Lignin for Supercapacitors

AbstractAs a waste of the pulp and papermaking industry, industrial alkali lignin (IAL) was employed to prepare nitrogen‐doped porous carbon by pre‐carbonizing of lignin under a N2 atmosphere at 400 °C and carbonizing with the assistance of urea at 800 °C for 1 h. The porosity and surface chemical properties of the obtained porous carbons strongly depended on the alkaline environment of the lignin. The obtained porous carbons showed specific surface areas ranging from 1.759 m2 g−1 to 1482 m2 g−1 and nitrogen contents of 1.12 % to 7.78 %. The unique microstructure and nitrogen functionalities endowed the porous carbon with a high capacitance of 283.4 F g−1 in 6 mol L−1 KOH aqueous electrolytes. In addition, the optimal porous carbon exhibited excellent rate capability (212.0 F g−1 at 20 A g−1) and cycle durability (97.6 % after 10000 charge‐discharge cycles), making it a promising electrode material for supercapacitors.

Identifying the dominant effect of electron-feeding on molybdenum phosphonates to decipher the activity origin for oxidative desulfurization of fuel

Electronic structure of active sites is crucial for oxidative desulfurization (ODS) process, while there is still a lack of direct experimental evidence to identify its real role on ODS activity. Herein, hollow spherical molybdenum phosphonate is designed through a facile hydrothermal method with the assistance of urea. The well-defined hollow spherical structure and homogeneous integration of organic moieties improve mass transfer during the heterogeneous ODS reaction. The combination of systemic characterizations, selective bromination and quenching experiment suggests that the introduction of –OH functional groups with strong electron-donating ability can modulate the electronic structure at molecular level, which provides continuous electron-feeding to Mo active sites, thus accelerating the ODS process. Correspondingly, the obtained catalyst delivers superior ODS performance with 100 % DBT conversion in 40 min at 60 ℃ and stable recyclability up to 10 times. This work can supply new inspiration for manipulating the nanostructures and electronic states of metal phosphonates for green catalysis.

Scalable Preparation of Low-Defect Graphene by Urea-Assisted Liquid-Phase Shear Exfoliation of Graphite and Its Application in Doxorubicin Analysis.

The mass production of graphene is of great interest for commercialization and industrial applications. Here, we demonstrate that high-quality graphene nanosheets can be produced in large quantities by liquid-phase shear exfoliation under ambient conditions in organic solvents, such as 1-methyl-2-pyrrolidinone (NMP), with the assistance of urea as a stabilizer. We can achieve low-defect graphene (LDG) using this approach, which is relatively simple and easily available, thereby rendering it to be an efficient route for the mass production of graphene. We also demonstrate the electrochemical sensing of an LDG-modified electrode for the determination of doxorubicin (DOX). The sensor shows an enhanced electrocatalytic property towards DOX, leading to a high sensitivity (7.23 × 10−1 μM/μA) with a detection limit of 39.3 nM (S/N = 3).

Urea-modified candle soot for enhanced anodic performance for fast-charging lithium-ion battery application

We demonstrate a facile synthesis method to modify the candle soot morphology with the assistance of urea as a porogen during combustion to enable its use as a binder-free anode. As obtained urea modified candle soot varies significantly in its physical and electrochemical properties compared to candle soot deposited directly by burning the candle. While we characterize the physiochemical properties thoroughly in this work using X-ray diffraction, Raman spectroscopy, N2 adsorption/desorption isotherms, scanning as well as high resolution transmission electron microscopy, electrochemical properties of as-fabricated modified candle soot anode shows an outstanding specific capacity of 520 and 260 mAhg−1 at 5C and 10 C-rates after 900 and 2000 galvanostatic charge-discharge cycles respectively. Due to the presence of extra mesoporosity in the modified candle soot along with nitrogen doping from urea, electrochemical performance is significantly improved as compared to bare candle soot. Further, full cell studies show that as modified nitrogen-doped candle soot can deliver a high capacity of 143 mAhg−1 at 50 mAg−1 current density with 312 Wh-kg−1 specific energy density. Excellent electrochemical behavior of as-modified nitrogen doped candle soot reveals the potency of this material as an anode for Li-ion battery for high current applications such as hybrid electric vehicles.

Ultrasound treated cerium oxide/tin oxide (CeO2/SnO2) nanocatalyst: A feasible approach and enhanced electrode material for sensing of anti-inflammatory drug 5-aminosalicylic acid in biological samples

In this work, we developed cerium oxide/tin oxide (CeO2/SnO2) nanocatalyst with the assistance of urea by a simple sonochemical method and utilized as an efficient electrode material for electrochemical sensing of anti-inflammatory drug 5-aminosalicylic acid (Mesalamine, MES). The CeO2/SnO2 nanoparticles (NPs) were systematically characterized in terms of their crystal structure, morphologies, and physicochemical properties using XRD, Raman, FESEM, HR-TEM, EDX, mapping, and XPS analysis. The characterization results clearly confirmed that the prepared NPs was formed in the phase of CeO2/SnO2 without any other impurities. The electrochemical properties of CeO2/SnO2 NPs were investigated by EIS, CV, and DPV techniques. The CeO2/SnO2 NPs (9.6 μA) modified GCE demonstrated an excellent and improved electrocatalytic activity in terms of higher anodic peak current and lower peak potential when compared to bare GCE (6.7 μA) and CeO2 NPs/GCE (8.2 μA) for the sensing of MES. The CeO2/SnO2 NPs/GCE shows broader linear response range and lower detection limit of 0.02–1572 μM and 0.006 μM, respectively. Moreover, other potentially interfering compounds such as a similar functional group containing biological substances and inorganic species have no interference effect towards MES sensing. In addition, the practicability of the CeO2/SnO2 NPs/GCE was tested by real sample analysis in commercial MES tablet, human urine, and serum samples with the appreciable recovery results.

Understanding Interfacial Mechanics and Mechanisms of Exfoliation and Stabilization of Graphene Using Urea/Glycerol Solvents

AbstractKnowledge of interfacial mechanics and mechanisms of liquid exfoliation and stabilization of graphene in green solvents is vitally important in advancing preparation and characterization of graphene‐based materials. In this work, molecular dynamics simulations are performed to investigate exfoliation and stabilization of graphene from graphite with the assistance of urea and glycerol hybrid solvents. It is shown that the parallel exfoliation of graphene requires far less external forces as compared with the perpendicular exfoliation. Among different mediums, the 1:2 molar ratio of urea to glycerol solution presents the smallest or even negligible resistive force in both directions due to the less compressed steric hindrance to graphene exfoliation and the optimal hydrogen bonds formed between the binary solvents. During the dispersion process, the urea molecules first wedge into the graphene interlayer and then facilitate the glycerol to diffuse around or inside of the interstice due to hydrogen bonding. The confined solvents form stable layered structure to solvate and stabilize the exfoliated graphene. This work is believed to provide atomic scale understanding of interfacial mechanics and mechanisms of liquid‐phase exfoliation and dispersion of graphene and other 2D materials in low‐cost and environmental‐friendly hybrid solvents.

N-Doped carbon nanofibers derived from bacterial cellulose as an excellent metal-free catalyst for selective oxidation of arylalkanes.

N-Doped carbon nanofibers derived from one-step pyrolysis of low-cost bacterial cellulose with the assistance of urea were reported. Owing to their interconnected nanofibrous structure and high specific surface area as well as high N doping, they exhibited excellent catalytic performance for selective oxidation of arylalkanes even with O2 as an oxidant in aqueous solution.

Highly mineralized chitosan-based material with large size, gradient mineral distribution and hierarchical structure

Nature materials constituted with organic and inorganic components have hierarchical structure and superior performance. Although a variety of techniques have been developed to mimic microstructure and properties of natural mineralized materials, facile and rapid fabrication of large-size bulk materials with high calcium content under ambient conditions still remains a major challenge. Here, we present a feasible and versatile route to a highly mineralized material with an in situ preparation method where gelation and mineralization occur simultaneously. Meanwhile, hierarchically ordered hydrogel microstructures are formed during the gelation, and controllable inorganic gradient distribution forms along with mineralization spontaneously. With the achievement of high mineral content by the assistance of urea, this fabrication route is facile and efficient, only taking several hours to complete the gelation and mineralization, and large-scale materials are prepared readily. This chitosan matrix-directed mineralization represents a rational and promising strategy for fast fabrication of highly mineralized material with hierarchical structure on a large scale, and the chitosan-based mineralized material has great potential for applications in bone repairing and tissue engineering.

3D Flower-Like Gadolinium Molybdate Catalyst for Efficient Detection and Degradation of Organophosphate Pesticide (Fenitrothion).

Three-dimensional (3D) nanostructured materials have received enormous attention in energy and environment remediation applications. Herein, we developed a novel 3D flower-like gadolinium molybdate (Gd2MoO6; GdM) and used as a bifunctional catalyst for the electrochemical detection and photocatalytic degradation of organophosphate pesticide fenitrothion (FNT). The flower-like GdM catalyst was prepared via a simple sol-gel technique with the assistance of urea and ethylene glycol. The properties of GdM were confirmed by various spectroscopic and analytical techniques. The GdM catalyst played a significant role in electrochemical reduction of FNT and results in a very low detection limit (5 nM), wide linear ranges (0.02-123; 173-1823 μM), and good sensitivity (1.36 μA μM-1 cm-2). Interestingly, the GdM electrocatalyst had good recoveries to FNT in soil and water sample analysis. In addition to trace level detection, the flower-like GdM was used as the photocatalyst which portrayed an excellent photocatalytic degradation behavior to eliminate the FNT in the aqueous system. The GdM photocatalyst could degrade above 99% of FNT under UV light irradiation with good stability even after five cycles.

Enhanced sunlight-driven photocatalytic performance of ZnO prepared with the assistance of urea

Enhanced sunlight-driven photocatalytic performance of ZnO prepared with the assistance of urea

Morphology-Modulated Mesoporous CuO Electrodes for Efficient Interfacial Contact in Nonenzymatic Glucose Sensors and High-Performance Supercapacitors

Surface texture of a nanostructured electrode plays a key role in electrochemical application. Here we reported the CuO microspheres with different nanostructures covered nickel foam skeleton obtained via controllable synthesis strategy with the assistance of urea, and their performance in nonenzymatic glucose sensor and supercapacitor applications. The suitable nanostructures are conductive to pave the way to provide sufficient interfacial contact between electrode and electrolyte. The twin CuO microspheres composed of ultrathin nanoslices being ∼6 nm in thickness and presented well-defined mesoporous nanostructure. The glucose sensor based on the twin CuO nanoslice sphere/Ni foam composite electrode had two wide linear response ranges with ultrahigh sensitivity of 1.864×104 μA mM−1 cm−2 from 1 μM to 100 μM and 160.6 μA mM−1 cm−2 from 1 mM to 8 mM, and a remarkable lower detection limit less than 60 nM (S/N = 3), with a response time as fast as 3 s. Besides, we demonstrated that the electrode was capable of delivering superior areal specific capacitance of 425 mF cm−2 at current density of 0.5 mA cm−2 with excellent cycling stability. Moreover, the investigation of the effects of CuO surface morphology on the interfacial processes can be extended to a wide range of electrochemical systems.

Bimetallic PtAu superlattice arrays: Highly electroactive and durable catalyst for oxygen reduction and methanol oxidation reactions

Abstract Superlattice arrays, an important type of nanomaterials, have wide applications in catalysis, optic/electronics and energy storage for the synergetic effects determined by both individual metals and collective interactions. Herein, a simple one-pot solvothermal coreduction approach is developed for facile preparation of bimetallic PtAu alloyed superlattice arrays (PtAu SLAs) in oleylamine, with the assistance of urea via hydrogen bonding induced self-assembly. Urea is essential in morphology-controlled process and prevents PtAu nanoparticles from the disordered aggregation. The characterization and formation mechanism of PtAu SLAs are investigated in details. The as-synthesized hybrid nanocrystals exhibit enhanced electrocatalytic performances for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in alkaline electrolyte in comparison with commercial Pt-C (50%, wt.%) and Pt black catalysts.

One-step wet-chemical synthesis of gold nanoflower chains as highly active surface-enhanced Raman scattering substrates

Well-defined gold nanoflower chains (Au NFCs) were simply fabricated on a large scale by a rapid, surfactant-free, seed-free, and template-free wet-chemical method, only with the assistance of urea. It was found that the synthesis and assembly of Au NFCs were almost simultaneously completed. The as-obtained Au nanostructures were primarily characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and UV–vis spectroscopy. The possible formation mechanism was discussed. The as-fabricated Au NFCs exhibited significant surface-enhanced Raman scattering (SERS) enhancement using p-aminothiophenol as a bench-model probe.

Urea-assisted synthesis of ultra-thin hexagonal tungsten trioxide photocatalyst sheets

Ultra-thin hexagonal tungsten trioxide (h-WO3) sheet has been synthesized with the assistance of urea. Some measurements have been carried out for sample characterization, such as XRD, TEM, AFM, FT-IR, Raman, XPS, and Zeta potential. It is shown that urea not only acts as pH regulator and stabilizer for the generation of a metastable hexagonal phase, but also plays an important role on the formation of ultra-thin sheet. The detailed formation mechanism has been discussed. The TEM and AFM tests show the thickness of ultra-thin h-WO3 nanosheet which is about 5 nm and the size is about 20–120 nm. Such size is favorable for photocatalytic reaction. Photodegradation RhB is carried out for investigating the photocatalytic activity of as-prepared sample. The ultra-thin h-WO3 sheet displays superior photocatalytic activity, more excellent photocatalytic activity than other shape samples due to its unique structure.

Preparation and electrochemical characteristic of porous NiO supported by sulfonated graphene for supercapacitors

NiO/sulfonated graphene(NiO/SGN) composites were fabricated under the assistance of urea as supercapacitor materials. The composites as prepared possess the leaf vein-like morphology, forming the porous structure that benefits the enhancement of pseudocapacitive performance. Moreover, the introduction of sulfonated graphene contributes to the surface hydroxylation of NiO, which may increase electrochemically active sites on the surface of NiO. The electrochemical measurements demonstrate that specific capacitances of NiO, NiO/thermally reduced graphene(NiO/TRG) and NiO/SGN are 200, 261 and 307Fg−1 at a current density of 5.0Ag−1 respectively, suggesting that the significant improvement of pseudocapacitive performance for NiO/SGN could be expected. The results from electrochemical impedance spectroscopy(EIS) demonstrate that sulfonated graphene can not only provide electron transport channels for its composites similar to thermally reduced graphene, but also benefit the electrolyte penetration in the composites compared with thermally reduced graphene.

Facile post-synthesis and photocatalytic activity of N-doped ZnO–SBA-15

N-doped ZnO–SBA-15 materials (denoted as nN–xZnO–SBA-15, where n is number of urea treatments and x is the weight ratio of ZnO/(ZnO+SBA-15)) were successfully synthesized by a two-step procedure. First, xZnO–SBA-15 was prepared by impregnating SBA-15 with Zn(NO3)2, followed by calcinating at 550°C. In the second step, xZnO–SBA-15 was modified n times by doping nitrogen with the assistance of urea. The resulting nN–xZnO–SBA-15 materials prepared with various numbers of urea treatments were characterized by XRD, TEM, SEM, EDS, N2 adsorption/desorption at 77K, diffuse reflectance UV–vis, and XPS. The results show that the nN–xZnO–SBA-15 maintains its ordered hexagonal mesostructure and exhibits light absorbance in the visible region. The nN–xZnO–SBA-15 samples were investigated with the photodegradation of methylene blue under visible light, and exhibited significant photocatalytic activity. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.

Facile Postsynthesis of N-Doped TiO2-SBA-15 and Its Photocatalytic Activity

N-doped TiO2-SBA-15 (denoted as N-TiO2-SBA-15) material has been successfully synthesized by a two-step procedure. Firstly, TiO2-SBA-15 was prepared by impregnating tetraisopropyl orthotitanate on SBA-15 and followed by calcination at 550°C. In the second step, TiO2-SBA-15 was modified by doping nitrogen with the assistance of urea. The resulting material, N-TiO2-SBA-15, was characterized by XRD, TEM, SEM, N2adsorption/desorption at 77 K, DR UV-Vis, and XPS. The results showed that N-TiO2-SBA-15 material maintains its ordered hexagonal mesostructure and exhibits the absorption of visible region. The photocatalytic activity of N-TiO2-SBA-15 sample was evaluated by the photodegradation of methylene blue under visible light.

Facile synthesis of novel Ag3PO4tetrapods and the {110} facets-dominated photocatalytic activity

Highly uniform silver orthophosphate microcrystals with novel tetrapod morphology are, for the first time, synthesized via a simple hydrothermal route with the assistance of urea. The effect of active crystal facets on the photocatalytic activity is principally investigated. The silver orthophosphate tetrapods exhibit significantly higher visible light activity than the polyhedrons for the degradation of toxic organic compounds due to the highly exposed {110} facets.

Synthesis of γ-Bi<sub>2</sub>MoO<sub>6</sub> Spheres and their Photocatalytic Activities for Degradation of Rhodamine B

A highly efficient γ-Bi2MoO6 photocatalyst was synthesized by a solvethermal method with the assistance of urea. The structure, morphology and photophysical properties of the Bi2MoO6 were characterized by X-ray diffraction, scanning electron microscope, UV–vis diffuse reflectance spectroscopy and nitrogen adsorption-desorption techniques. The photocatalytic efficiencies were evaluated by the degradation of rhodamine B (RhB) under visible-light irradiation, and the γ-Bi2MoO6 structures displayed significantly higher visible-light-driven photocatalytic activity in comparison to TiO2 nanoparticles.