In this paper, Ag-Functionalized graphene electrocatalyst was prepared by simultaneous reduction of Ag[(NH3)2]+ and graphene oxide (GO) under the protection of Poly Diallyldimethylammonium Chloride. The as-prepared catalyst was utilized to enhance the catalytic activity toward oxygen reduction reaction (ORR) in energy-saving electrolysis of Na2CO3. The morphology characterization indicates that Ag nanoparticles uniformly disperse on the surface of reduced graphene oxide (RGO), and their average size is only about 5.7 nm. The electrochemical tests show that the as-prepared catalyst exhibits high electrocatlytic activity for ORR in alkaline media. Furthermore, when the catalyst is used for the oxygen reduction cathode (ORC) in the galvanostatic electrolysis of Na2CO3, the cell voltage can be reduced by 1.05 V, as compared with the conventional hydrogen evolution cathode (HEC) electrolysis. Correspondingly, up to 41.5% electrical energy consumption is saved at the same current density of 100 mA cm–2.

•Synthesis and characterization of Nobel metal nanoparticles•Biological applications•Physical and chemical method to nanoparticle synthesis•Anti-cancer properties of green synthesis nanoparticlesSynthesis of Nobel metal nanoparticles, play a key role in the field of medicine. Plants contain a substantial number of organic constituents, like phenolic compounds and various types of glycosides that help in synthesis of metal nanoparticles. Synthesis of metal nanoparticles by green method is one of the best and environment friendly methods. The major significance of the green synthesis is lack of toxic by-products produced during metal nanoparticle synthesis. The nanoparticles, synthesized by green method show various significant biological activities. Most of the research articles report the synthesized nanoparticles to be active against gram positive and gram negative bacteria. Some of these bacteria include Escherichia coli, Bacillus subtilis, Klebsiella pneumonia and Pseudomonas fluorescens. The synthesized nanoparticles also show significant antifungal activity against Trichophyton simii, Trichophyton mentagrophytes and Trichophyton rubrum as well as different types of cancer cells such as breast cancer cell line. They also exhibit significant antioxidant activity. The activities of these Nobel metal nano-particles mainly depend on the size and shape. The particles of small size with large surface area show good activity in the field of medicine. The synthesized nanoparticles are also active against leishmanial diseases. This research article explores in detail the green synthesis of the nanoparticles and their uses thereof.

•Biomass-derived carbon with nitrogen and cobalt doping (NPACCo) was prepared.•NPACCo contains high content of quaternary-N and pyridinic-N.•NPACCo shows co-existence of amorphous and short-range ordered carbon.•NPACCo exhibits an impressive high supercapacitive performance.•NPACCo shows high onset potential, diffusion current and selectivity for ORR.Biomass-derived carbon by activation with nitrogen and cobalt (denoted as NPACCo) was prepared by one-pot pyrolysis of pomelo peel with melamine, cobalt nitrate and potassium hydroxide, followed by acid leaching. NPACCo possesses high content of quaternary-N (2.5%) and pyridinic-N (1.7%), co-existences of amorphous and short-range ordered carbon, high specific surface area and pore structure with majority of micropores and small mesopores. As electrode material of supercapacitors, NPACCo exhibits high specific capacitance and good rate capability. At ultrahigh rate of 50 A g−1 (135 mA cm−2), the capacitance of NPACCo remains 246 F g−1, which is 6.3, 1.9 and 3.2 times as high as that of other three materials (PC, PAC and NPAC). The as-assembled symmetric supercapacitor of NPACCo delivers high energy density, high power density and excellent cycling stability. With respect to oxygen reduction reaction (ORR), NPACCo exhibits high onset potential (0.87 V), high half-wave potential (0.78 V), excellent methanol tolerance and low yield of H2O2. The ORR properties of NPACCo are comparable or superior to those of commercial Pt/C. This investigation of pomelo peel-based NPACCo would be valuable for development of both supercapacitor and ORR.Download high-res image (138KB)Download full-size image

Hydroxyl radicals (˙OH) generated by oxygen reduction reaction (ORR) were believed to be responsible for the electrochemical depolymerization of lignin in our previous study. However, the mechanism research was hard to carry out due to the recalcitrant nature of lignin. In this paper, 4-benzyloxyl phenol (PBP) and benzyl phenyl ether (BPE) were employed as lignin model compounds (LMCs). Based on the qualitative and quantitative analysis of the degradation products, a mechanism was put forward, which is that the in situ generated ˙OH selectively attacked the active site opposite to the phenolic hydroxyl group and induced the cleavage of the alkyl-O-aryl ether bond. The proposed mechanism was further verified by the electrochemical degradation of PBP under controlled conditions, which showed a positive correlation between the degradation efficiency of PBP and the concentration of in situ generated ˙OH radicals.

Due to the technology advancement and the large-scale application of lithium-ion batteries in recent years, the market demand for lithium is growing rapidly and the availability of land lithium resources is decreasing significantly. As such, the focus of lithium extraction technologies has shifted to water lithium resources involving salt-lake brines and sea water. Among various aqueous recovery technologies, the lithium ion-sieve (LIS) technology is considered the most promising one. This is because LISs are excellent adsorbents with high lithium uptake capacity, superior lithium selectivity and good cycle performance. These attributes have enabled LISs to separate lithium effectively from aqueous solutions containing different ions. The present work reviews the latest development in LIS technology, including the chemical structures of ion-sieves, the corresponding lithium adsorption/desorption mechanisms, the ion-sieves preparation methods, and the challenges associated with the lithium recovery from aqueous solutions by the LIS batteries. Besides, some common LIS composite materials forming technologies, including granulation, foaming, membrane and fiber formation, and magnetization, which are used to overcome the shortcomings in industrial column operations, are also explored.

Although N-doped graphene-based electrocatalysts have shown good performance for oxygen reduction reaction (ORR), they still suffer from the single-type active site in the as-prepared catalyst, limited accessible active surface area because of easy aggregation of graphene, and harsh condition for preparation process of graphene. Therefore, further developing a novel type of graphene-based electrocatalyst by a facile and environmentally benign method is highly anticipated. Herein, we first fabricate a sandwich-like graphene/carbon hybrid using graphene oxide (GO) and nontoxic starch. Then the graphene/carbon hybrid undergoes postprocessing with iron(III) chloride (FeCl3) and potassium sulfocyanide (KSCN) to acquire N-doped graphene/carbon nanosheets decorated by Fe and S. The resultant displays the features of interpenetrated three-dimensional hierarchical architecture composed of abundant sandwich-like graphene/carbon nanosheets and low graphene content in as-prepared sample. Remarkably, the obtained catalyst possesses favorable kinetic activity due to the unique structure and synergistic effect of N, S, and Fe on ORR, showing high onset potential, low Tafel slope, and nearly four-electron pathway. Meanwhile, the catalyst exhibits strong methanol tolerance and excellent long-term durability. In view of the multiple active sites, unique hierarchical structure, low graphene content, and outstanding electrochemical activity of the as-prepared sample, this work could broaden the thinking to develop more highly efficient graphene/carbon electrocatalysts for ORR in fuel cells.

Hierarchical nitrogen-doped porous graphene/carbon (NPGC) composites were fabricated by a simple and nontemplate method. The morphology characterizations demonstrate that reduced graphene oxide was successfully coated by the carbon derived from glucose, and a well-organized and interpenetrated hierarchical porous structure of NPGC was formed after pyrolysis at 950 °C. Notably, the prepared material, denoted as NPGC-950, has superlarge specific surface area (1510.83 m2 g–1) and relatively high content percentage of pyridinic and graphitic nitrogen. As an efficient metal-free electrocatalyst, NPGC-950 exhibits a high onset potential (0.91 V vs RHE) and a nearly four-electron pathway for oxygen reduction reaction in alkaline solution as well as stronger methanol tolerance and better long-term durability than commercial Pt/C. In view of these excellent features, the obtained hierarchical N-doped metal-free porous carbon material is a promising catalyst for oxygen reduction reaction and could be widely applied in industry.Keywords: graphene/carbon composites; hierarchical porous structure; metal-free; nitrogen doped; oxygen reduction reaction

•Carbon submicrospheres prepared from glucose own high density of hydroxyl groups.•HCSs exhibit high sensitivity to NB with a favorably low background current.•The H-bonding and electron donor-acceptor complex between HCSs and NB are crucial.•HCSs exhibit well-defined peaks for sensing of NB, DNB and TNB, respectively.To explore the active sites for detection of nitroaromatic compounds and improve the sensing performance of carbon based materials, the commercial carbon nanoparticles (CNPs), nitric acid pre-oxidized carbon nanoparticles (OCNPs) and hydroxyl-rich carbon submicrospheres (HCSs) were systematically investigated by transmission electron microscopy, infrared spectroscopy, X-ray photoelectron spectra and electrochemical tests. OCNPs, prepared from CNPs by HNO3 oxidation, contain amounts of oxygen functional groups (OFG) including –COOH, –OH, CO and so on. HCSs, prepared by the green and facile hydrothermal carbonization of glucose, possess the highest loading of hydroxyl groups (approximately 80% of total surface oxygen-containing groups) among these carbon materials. The HCSs modified electrode exhibits the highest current response to nitrobenzene (NB), accompanied by a favorably low background current which is only 30% of that for OCNPs. The excellent sensing performance is attributed to the abundant hydroxyl groups, which facilitate the formation of H-bonding and charge-transfer interaction between electron-donating hydroxyl groups on HCSs and electron-deficiency nitroaromatic molecules. The further investigation by square wave voltammetry indicates that the HCSs modified electrode exhibits a series of well-defined current peaks for NB, dinitrobenzene (DNB) and trinitrobenzene (TNB) with high sensitivity (>6 nA μg−1 L) and low detection limit (0.88 ∼ 1.8 μg L−1). Moreover, the proposed sensor exhibits high reproducibility, satisfactory storage stability and good anti-interference ability.

A three-dimensional (3D) structured electrode in which a compact CeO2-β-PbO2 particle layer on each carbon fiber in the felt (denoted as CF/CeO2-β-PbO2) was fabricated using cyclic voltammetry (CV) method in the presence of CeO2 nanoparticles in the electrolyte and supposed to be used as a sensor for in situ chemical oxygen demand (COD) detection. It was found that CeO2 was codeposited with PbO2 onto the anode, and the deposited crystals were tiny and compacted with each other. The electrochemical behaviors demonstrate that the fabricated CF/CeO2-β-PbO2 electrode possesses larger effective surface area, higher electrochemically catalytic activity, and better mechanical stability as compared with the anode without CeO2 deposited by CV method or constant potential (CP) method. The results of COD determination by the fabricated CF/CeO2-β-PbO2 electrode show a sensitivity of (3.0 ± 0.02) × 10−3 mA cm−2/mg L−1, a detection limit of 3.6 mg L−1 (S/N = 3) and a linear range of 30–8500 mg L−1 with correlation coefficient (R) of 0.9985 and RSD within 5 %.

•Synthesis of silver nano particles using Caruluma edulis plant extract.•Characterizations of silver nanoparticles by UV, FTIR, HRTEM and EDX.•Photo catalytic, antimicrobial and anti-oxidant activity of silver nanoparticles.•Reduction of phenolic compounds at modified GC/AgNP electrode.•Cyclic voltammetric study of bromothymol blue at GC/AgNP modified past electrode.In the present research work a novel, nontoxic and ecofriendly procedure was developed for the green synthesis of silver nano particle (AgNPs) using Caruluma edulis (C. edulis) extract act as reductant as well as stabilizer agents. The formation of AgNPs was confirmed by UV/Vis spectroscopy. The small and spherical sizes of AgNPs were conformed from high resolution transmission electron microscopy (HRTEM) analysis and were found in the range of 2–10 nm, which were highly dispersion without any aggregation. The crystalline structure of AgNPs was conformed from X-ray diffraction (XRD) analysis. For the elemental composition EDX was used and FTIR helped to determine the type of organic compounds in the extract. The potential electrochemical property of modified silver electrode was also studied. The AgNPs showed prominent antibacterial motion with MIC values of 125 μg/mL against Bacillus subtilis and Staphylococcus aureus while 250 μg/mL against Escherichia coli. High cell constituents' release was exhibited by B. subtilis with 2 × MIC value of silver nanoparticles. Silver nanoparticles also showed significant DPPH free radical scavenging activity. This research would have an important implication for the synthesis of more efficient antimicrobial and antioxidant agent. The AgNP modified electrode (GC/AgNPs) exhibited an excellent electro-catalytic activity toward the redox reaction of phenolic compounds. The AgNPs were evaluated for electrochemical degradation of bromothymol blue (BTB) dyes which showed a significant activity. From the strong reductive properties it is obvious that AgNPs can be used in water sanitization and converting some organic perilous in to non-hazardous materials. The AgNPs showed potential applications in the field of electro chemistry, sensor, catalyst, nano-devices and medical.

Lignin, a natural macromolecule containing substantial aromatic rings and abundant hydroxyl groups, was firstly chemically grafted with phosphorus–nitrogen-containing groups via a liquefaction–esterification–salification process to prepare lignin-based phosphate melamine compound (LPMC). And then the LPMC which has remaining hydroxyl groups was used to substitute parts of polyols and copolymerize with isocyanate to produce lignin-modified-PU foam (PU-LPMC) with excellent flame retardancy. Owing to the rigid aromatic structure of lignin and the covalent linkages between LPMC and the polymer–matrix, PU-LPMC showed a nearly 2-fold increase in compression strength and excellent performance of thermal stability, char residue formation, self-extinguishment and inhibition from melt-dripping and smoke generation. Moreover, a large amount of non-flammable gases were released during thermal degradation and a compact and dense intumescent (C–P–N–O)x char layer formed on the surface of the foams after combustion, resulting in the improvement of anti-flaming properties of the polymer by the flame retardancy of both gas phase and condensed phase.

Electrochemical depolymerization of lignin for production of renewable aromatic compounds is presented. In the designed non-diaphragm electrolytic cell, lignin in alkaline electrolyte was directly electro-oxidized on the anode and chemically oxidized by the electro-generated H2O2 formed on the cathode simultaneously. The linkages among C9 units in lignin were broken down and more than 20 kinds of low-molecular-weight (LMW) aromatic compounds containing hydroxyl, aldehyde, carbonyl and carboxyl groups were generated and identified by GC-MS and ESI-MS/MS measurements. The effects of electrolysis conditions on the concentration of H2O2, the decomposition rate of H2O2 into reactive oxygen species (ROS) and the yields of LMW products were investigated in detail. Results show that H2O2 and ROS play very important roles in lignin depolymerization. The electrolysis conditions for producing higher concentrations of H2O2 and ROS are in favor of giving higher yields of LMW products. 59.2% of lignin was depolymerized into LMW products after 1 hour-electrolysis at 80 °C under a current density of 8 mA cm−2 with extra O2 supplement.

Lignin is a natural aromatic macromolecule in huge quantity and might serve as sustainable resources for the chemical industry after being depolymerized. An electrochemical approach combining anode oxidation and electro-generated H2O2 oxidation has been developed for converting lignin into value-added aromatic chemicals in this study. Lignin in alkali solution was electrolyzed in an undivided electrolytic cell with a cylindrical graphite felt cathode and a RuO2–IrO2/Ti mesh anode, in which the by-product O2 on the anode could be efficiently reduced to H2O2 on the cathode in situ. Results display that the depolymerization productivity via the integrated approach obviously surpassed the sum of that by separate H2O2 oxidation and anode oxidation. Moreover, the analysis results of GC-MS, GPC, and C9 expanded formula confirmed that C–C bonds and C–O–C bonds in lignin were cleaved synergistically by direct anodic oxidation and indirect H2O2 oxidation, and the macromolecules are gradually depolymerized into final products of monomers and dimers.

This paper reports an energy-saving electrolysis of Na2CO3 to generate NaHCO3 and NaOH for efficient production of alumina. Silver nanoparticles catalyzed oxygen reduction cathode (Ag NPs ORC) is employed to substitute conventional cathode (hydrogen evolution cathode: HEC). Scanning electron microscopy (SEM) image shows that silver nanoparticles ranging from 15 to 50 nm are evenly distributed on the surface of the carbon support. The constant current electrolysis indicates that the cell voltage of Ag NPs ORC electrolysis of Na2CO3 is as low as 1.52 V and correspondingly the electrical energy consumption is saved up to 39.8% as compared to HEC electrolysis at the same current density of 100 mA cm− 2.It reports an energy-saving electrolysis of Na2CO3 by using sliver nanoparticles catalyzed oxygen reduction cathode (ORC) to substitute hydrogen evolution cathode (HEC). The electrical energy consumption of ORC electrolysis is saved up to 39.8% as compared to that of conventional HEC electrolysis.Highlights► This paper reports an energy-saving electrolysis of Na2CO3 by using Ag NPs ORC. ► Silver nanoparticles ranging from 15 to 50 nm are evenly distributed on ORC. ► The cell voltage of ORC-electrolysis is as low as 1.52 V at 100 mA cm− 2. ► The electrical energy consumption is saved up to 39.8% as compared to that of HEC electrolysis.

An electrochemical process for producing potassium iodate based on oxidation of KI coupled with oxygen reduction reaction in a newly designed cell is reported. By using an Ag-modified oxygen reduction cathode, the proposed cell needed no ion exchange membrane, and the current efficiency for KIO3 was confirmed to be over 96%, the corresponding cell voltage was only 0.7–0.8 V.

Because the supply of bauxite ores in many countries is becoming deficient, a process of preparing alumina from an alternative resource, namely, kaolin, is proposed in this work. First, kaolin was heated at 600 °C for 2 h before being leached with 1 M citric acid solution, about 75% of the Al in kaolin entered the leachate as aluminum citrate (AlCit) solution. Then, about 50% of the Al(III) in the leachate could be precipitated as ammonium aluminum carbonate hydroxide (AACH) by addition of NH4HCO3 at pH 9.00 ± 0.50. The morphology of AACH characterized by SEM and TEM was spherical particles composed of many nanorods with sizes of about 500 × 25 nm. Finally, mesoporous γ-Al2O3 was obtained by roasting AACH at 700 °C. The Fe and Na contents in the obtained γ-Al2O3 product determined by XRD and ICP-AES were 2 and 0.1 ppm, respectively. The obtained γ-Al2O3 had a morphology similar to that of AACH, and its BET surface area was as high as 235.2 m2/g.

The candidature of Fe−Si and Mg−Al alloys at millimeter-scale particle sizes for chemical degradation of disinfection byproducts (DBPs) in drinking water systems was substantiated by their enhanced corrosion resistance and catalytic effect on the degradation. The Mg−Al particles supplied electrons for reductive degradation, and the Fe−Si particles acted as a catalyst and provided the sites for the reaction. The alloy particles are obtained by mechanical milling and stable under ambient conditions. The proposed method for chemical degradation of DBPs possesses the advantages of relatively constant degradation performance, long-term durability, no secondary contamination, and ease of handling, storage and maintenance in comparison with nanoparticle systems.

It is a promising technology in the alumina industry using citric acid to extract aluminum from clay or kaolin and obtain the solution of aluminum citrate (AlCit). But the prerequisite of the preparation procedure of alumina started from AlCit is that citric acid should be recycled. A process named AlCit−Dawsonite−alumina is proposed in this paper. By using Dawsonite as an intermediate, citrate groups could be separated and reused. The process was verified in laboratory scale: First, Dawsonite was precipitated from AlCit solution with a satisfied purity and conversion rate. Second, Dawsonite was transformed to alumina with low Na content through the two proposed methods. The structure and purity of the intermediate of Dawsonite and products of alumina were characterized by infrared, thermogravimetric−differential thermal analysis, X-ray diffraction, scanning electron microscopy, and inductively coupled plasma. The results show that the synthesized Dawsonite has a great purity and perfect crystallinity; and the Na content of the final alumina product is lower than 0.2%.

The present paper reports the synthesis, characterization and electrochemical properties of a nano-structured AgO material. The studies results show that the nano-structured AgO electrode still has good electrochemical characteristics at a charge and discharge current as high as 10000 mA g−1. The electrode offers a discharge voltage of 1.4 V, a discharge capacity of 360 mAh g−1 and an exciting specific power density up to 14 kW kg−1, much higher than the current level of ca. 1–2.5 kW kg−1 for existing secondary batteries and super capacitors. The super high speed ability of charge/discharge makes the charge or discharge time of the electrode shorter than 2 min 53 s.

NiOOH was prepared by one-step electrolysis of spherical Ni(OH)2 and the effects of electrolysis parameters were examined. The highly pure NiOOH was obtained after electrolysis at a current density of 60mA.g-1 and 30°C with anodic potential controlled in the range of 1.73–1.85V (vs. Zn/ZnO) for 360min. The NiOOH samples were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM) analysis. Results indicate that the electrolysis product is spherical NiOOH doped with graphite. Charge and discharge tests show that the prepared NiOOH offers a discharge capacity of over 270mAh.g-1 at current density of 30mA.g-1 and can be directly used as cathode material of alkaline Zn/NiOOH batteries. Galvanostatic charge/discharge and cyclic voltammetry (CV) tests reveal good cycling reversibility of the NiOOH electrode.

Ionic liquids due to their advantageous properties gain importance in many fields. This study aims to overview the use of ionic liquids in the selective partial fluorination of organic compounds through electrochemical method. In addition to ionic liquid based fluorination, the earlier approaches of fluorination through an electrochemical process have also been highlighted. The factors such as electrode materials (Pt, Ni, and C), types of solvents (CH3CN, DMC, THF, DME, Sulfone, etc.) and type of electrolytes (Et3N·3HF, Et3NF·3HF, py·HF, etc.) which affect the electrochemical fluorination of organic compounds have been reviewed. For electrode preparation, the carbon, platinum and nickel were considered suitable materials to be used as an electrode. In CH3CN media, Et3N·3HF and Et4NF·3HF showed better efficiency during fluorination of organic compounds. Solvent play an important role in electrochemical fluorination of organic compounds, with the change of solvent the percentage yield is highly affected. Py-HF is a convenient solvent-supporting electrolyte medium with a reasonably good conductivity. The electrolyte containing solvents have some side effects on electrochemical fluorination of organic compounds as observed in cyclic voltammetric analysis. Therefore electrochemical fluorination to organic compounds without the use of solvent gained more importance. The ionic liquids have been reported for its dual properties, as solvent as well as a fluorinating agent for organic compounds in electrochemical processes. It has been concluded that solvents free electrochemical fluorination of organic compounds gives good results as compare to solvent based. Ionic liquids due to more oxidative stability were noted to have considerable effect on the yield and selectivity of organic compound fluorination.Download full-size image

The present paper reports the synthesis, characterization and electrochemical properties of a nano-structured AgO material. The studies results show that the nano-structured AgO electrode still has good electrochemical characteristics at a charge and discharge current as high as 10000 mA g−1. The electrode offers a discharge voltage of 1.4 V, a discharge capacity of 360 mAh g−1 and an exciting specific power density up to 14 kW kg−1, much higher than the current level of ca. 1–2.5 kW kg−1 for existing secondary batteries and super capacitors. The super high speed ability of charge/discharge makes the charge or discharge time of the electrode shorter than 2 min 53 s.