Room-temperature synthesis of 2D-Ti3C2Tx nano-sheets by organic base treatment.

The growing demand for improved electrochemical performance in energy storage systems has stimulated research into advanced two-dimensional (2D) materials for electrodes. In this work, we obtain a layered MXene compound by exfoliating a titanium aluminum carbide precursor using tetramethylammonium hydroxide (TMAOH) ions in a full room temperature process followed by manual shaking. The hexagonal crystal structure and composition of the layered materials are characterized using different techniques. X-Ray diffraction shows the formation of 2D nano-sheets before and after the TMAOH treatment via its characteristic (002) diffraction peak, bringing to light an increase in the interlayer spacing after treatment. Scanning electron microscopy images confirm the layered morphology, whose composition is determined by energy dispersive x-ray analysis for the bulk material and by x-ray photoelectron spectroscopy for the surface of the obtained compounds. This study demonstrates a promising route to enhance delamination of this MXene 2D material in a low-cost room-temperature approach.

Enhancement of Li/S Battery Performance by a Modified Reduced Graphene Oxide Carbon Host Decorated with MoO3.

Electrochemical energy storage systems based on sulfur and lithium can theoretically deliver high energy with the further benefit of low cost. However, the working mechanism of this device involves the dissolution of sulfur to high-molecular weight lithium polysulfides (LiPs with general formula Li2Sn, n≥4) in the electrolyte during the discharge process. Therefore, the resulting migration of partially dissociated LiPs by diffusion or under the effect of the electric field to the lithium anode, activates an internal shuttle mechanism, reduces the active material and in general leads to loss of performance and cycling stability. These drawbacks poses challenges to the commercialization of Li/S cells in the short term. In this study, we report on the decoration of reduced graphene oxide with MoO3 particles to enhance interactions with LiPs and retain sulfur at the cathode side. The combination of experiments and density functional theory calculations demonstrated improvements in binding interactions between the cathode and sulfur species, enhancing the cycling stability of the Li/S cells.

Effects of Difluoro(oxalato)borate-Based Ionic Liquid as Electrolyte Additive for Li-Ion Batteries.

In this work, the use of N-methyl-N-propylpiperidinium difluoro(oxalato)borate Pip13DFOB ionic liquid (IL), originally synthesized in our laboratory, as an additive for liquid electrolytes in lithium-ion batteries (LIBs), is proposed. The synthesized IL exhibits glass and melting transitions at -70.9 °C and 17.1 °C, respectively, and a thermal decomposition temperature over 230 °C. A mixture based on 1.0 M LiPF6 in 1:1 v/v ethylene carbonate (EC): dimethyl carbonate (DMC) electrolyte solution (so called LP30) and the IL was prepared and tested in lithium metal cells versus two different commercially available carbonaceous electrodes, i.e., graphite (KS6) and graphene (GnP), and versus a high voltage LiNi0.5Mn1.5O4 (LNMO) cathode. A noticeable improvement was observed for Li|LNMO cells with an IL-added electrolyte, which exhibited a high specific capacity above 120 mAh g-1 with a Coulombic efficiency above 93% throughout 200 cycles, while the efficiency fell below 80% after 80 cycles with the absence of IL. The results confirm that the IL is promising additive for the electrolyte, especially for a longer cycle life of high-voltage cells.

Silicon-Based Composite Anodes for All-Solid-State Lithium-Ion Batteries Conceived by a Mixture Design Approach.

Silicon-based anodes composed of micrometric Si, graphite (MAG), LiI-Li3 PS4 solid electrolyte (LPSI), and carbon nanofiber (CNF), which can be prepared by straightforward manual grinding, are proposed in this study. The relation between composition and performance of the anodes is investigated through the mixture design approach, which allows discrimination of the effect of each component and also the combined effect of the components on the end performance. By increasing the fraction of LPSI in the anode, the capacity of the electrode is improved, and the best performance is obtained when the Si/MAG/LPSI ratio is 15 : 15 : 70. This composite integrated with 5 wt % CNF exhibits a capacity above 1200 mAh g-1 throughout 50 cycles in a bulk-type all-solid-state battery with LPSI as the electrolyte. Scanning electron microscopy (SEM) confirms that the presence of LPSI suppresses the aggregation of Si and improves the ratio of Si available for lithiation/delithiation.

Removal of Copper Corrosion Products by Using Green Deep Eutectic Solvent and Bio-Derivative Cellulose Membrane.

A safe and environmentally friendly material for corrosion removal from metals is proposed in this article. Electrochemically corroded copper was selected as a target material, and a deep eutectic solvent (DES) composed of choline chloride and ascorbic acid, in a molar ratio of 2:1, was developed to this end. Aqueous solutions of the DES with a concentration above 70 wt% were found to be effective in the dissolution of patina and less aggressive towards other materials such as CaCO3, which is the main component of limestone. These concentrated DES solutions were integrated with either cotton swabs or cellulose-based membranes and used for the cleaning of electrochemically corroded copper. The membrane containing 80 wt% DES aqueous solution exhibited the most desirable cleaning ability in terms of speed and area selectivity. X-ray diffraction analysis of the corroded copper before and after the application of the membrane was performed to demonstrate the successful corrosion removal.

Extraction of Emerging Contaminants from Environmental Waters and Urine by Dispersive Liquid-Liquid Microextraction with Solidification of the Floating Organic Droplet Using Fenchol:Acetic Acid Deep Eutectic Mixtures.

In this work, several eutectic mixtures formed by fenchol and acetic acid at seven molar ratios (between 4:1 and 1:4) were characterized and studied for the first time for their possible application as extraction solvents in dispersive liquid-liquid microextraction based on the solidification of the floating organic droplet (DLLME-SFO). A group of 13 emerging contaminants (gemfibrozil, bisphenol F, bisphenol A, 17ß-estradiol, testosterone, estrone, levonorgestrel, 4-tert-octylphenol, butyl benzyl phthalate, dibutyl phthalate, 4-octylphenol, 4-nonylphenol, and dihexyl phthalate) was selected and determined by liquid chromatography with ultraviolet and tandem mass spectrometry detection. Among the studied mixtures, only those of 2:1 and 1:1 provided the suitable features from an operational and repeatability point of view, suggesting that several eutectic mixtures of the same components may also provide similar results. Once the extraction conditions of both mixtures were optimized, the method was applied to the extraction of sea water, urine, and wastewater at different concentration levels, allowing the achievement of absolute recovery values between 49 and 100% for most analytes with relative standard deviation values below 19%. In addition, several samples of each type were analyzed, finding bisphenol A and gemfibrozil in some of them. The greenness of the method was also evaluated using the AGREEprep metric. The DLLME-SFO procedure was found to be very simple, quick, and effective and with a good sample throughput.

Upcycling Real Waste Mixed Lithium-Ion Batteries by Simultaneous Production of rGO and Lithium-Manganese-Rich Cathode Material.

The direct synthesis of high-value products from end-of-life Li-ion batteries (LIBs), avoiding the complex and costly separation of the different elements, can be reached through a competitive recycling strategy. Here, we propose the simultaneous synthesis of reduced graphene oxide (rGO) and lithium-manganese-rich (Li1.2Mn0.55Ni0.15Co0.1O2 - LMR) cathode material from end-of-life LIBs. The electrode powder recovered after LIBs mechanical pretreatment was directly subjected to the Hummers' method. This way, quantitative extraction of the target metals (Co, Ni, Mn) and oxidation of graphite to graphene oxide (GO) were simultaneously achieved, and a Mn-rich metal solution resulted after GO filtration, owing to the use of KMnO4 as an oxidizing agent. This solution, which would routinely constitute a heavy-metal liquid waste, was directly employed for the synthesis of Li1.2Mn0.55Ni0.15Co0.1O2 cathode material. XPS measurements demonstrate the presence in the synthesized LMR of Cu2+, SO4 2-, and SiO4 4- impurities, which were previously proposed as effective doping species and can thus explain the improved electrochemical performance of recovered LMR. The GO recovered by filtration was reduced to rGO by using ascorbic acid. To evaluate the role of graphite lithiation/delithiation during battery cycling on rGO production, the implemented synthesis procedure was replicated starting from commercial graphite and from the graphite recovered by a consolidated acidic-reductive leaching procedure for metals extraction. Raman and XPS analysis disclosed that cyclic lithiation/delithiation of graphite during battery life cycle facilitates the graphite exfoliation and thus significantly increases conversion to rGO.

Composite Nafion-CaTiO3-δ Membranes as Electrolyte Component for PEM Fuel Cells.

Manufacturing new electrolytes with high ionic conductivity has been a crucial challenge in the development and large-scale distribution of fuel cell devices. In this work, we present two Nafion composite membranes containing a non-stoichiometric calcium titanate perovskite (CaTiO3-δ) as a filler. These membranes are proposed as a proton exchange electrolyte for Polymer Electrolyte Membrane (PEM) fuel cell devices. More precisely, two different perovskite concentrations of 5 wt% and 10 wt%, with respect to Nafion, are considered. The structural, morphological, and chemical properties of the composite membranes are studied, revealing an inhomogeneous distribution of the filler within the polymer matrix. Direct methanol fuel cell (DMFC) tests, at 110 °C and 2 M methanol concentration, were also performed. It was observed that the membrane containing 5 wt% of the additive allows the highest cell performance in comparison to the other samples, with a maximum power density of about 70 mW cm-2 at 200 mA cm-2. Consequently, the ability of the perovskite structure to support proton carriers is here confirmed, suggesting an interesting strategy to obtain successful materials for electrochemical devices.

Polymer Electrolyte Membranes Based on Nafion and a Superacidic Inorganic Additive for Fuel Cell Applications.

Nafion composite membranes, containing different amounts of mesoporous sulfated titanium oxide (TiO2-SO4) were prepared by solvent-casting and tested in proton exchange membrane fuel cells (PEMFCs), operating at very low humidification levels. The TiO2-SO4 additive was originally synthesized by a sol-gel method and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and ion exchange capacity (IEC). Peculiar properties of the composite membranes, such as the thermal transitions and ion exchange capacity, were investigated and here discussed. When used as an electrolyte in the fuel cell, the composite membrane guaranteed an improvement with respect to bare Nafion systems at 30% relative humidity and 110 °C, exhibiting higher power and current densities.

Composite Nafion Membranes with CaTiO3-δ Additive for Possible Applications in Electrochemical Devices.

A composite membrane based on a Nafion polymer matrix incorporating a non-stoichiometric calcium titanium oxide (CaTiO3-δ) additive was synthesized and characterized by means of thermal analysis, dynamic mechanical analysis, and broadband dielectric spectroscopy at different filler contents; namely two concentrations of 5 and 10 wt.% of the CaTiO3-δ additive, with respect to the dry Nafion content, were considered. The membrane with the lower amount of additive displayed the highest water affinity and the highest conductivity, indicating that a too-high dose of additive can be detrimental for these particular properties. The mechanical properties of the composite membranes are similar to those of the plain Nafion membrane and are even slightly improved by the filler addition. These findings indicate that perovskite oxides can be useful as a water-retention and reinforcing additive in low-humidity proton-exchange membranes.

Gel Polymer Electrolytes Based on Silica-Added Poly(ethylene oxide) Electrospun Membranes for Lithium Batteries.

Solid polymer electrolytes, in the form of membranes, offering high chemical and mechanical stability, while maintaining good ionic conductivity, are envisaged as a possible solution to improve performances and safety in different lithium cell configurations. In this work, we designed and prepared systems formed using innovative nanocomposite polymer membranes, based on high molecular weight poly(ethylene oxide) (PEO) and silica nanopowders, produced by the electrospinning technique. These membranes were subsequently gelled with solutions based on aprotic ionic liquid, carbonate solvents, and lithium salt. The addition of polysulfide species to the electrolyte solution was also considered, in view of potential applications in lithium-sulfur cells. The morphology of the electrospun pristine membranes was evaluated using scanning electron microscopy. Stability and thermal properties of pristine and gelled systems were investigated uisng differential scanning calorimetry and thermal gravimetric analysis. Electrochemical impedance spectroscopy was used to determine the conductivity of both swelling solutions and gelled membranes, allowing insight into the ion transport mechanism within the proposed composite electrolytes.

Screening and Assessment of Low-Molecular-Weight Biomarkers of Milk from Cow and Water Buffalo: An Alternative Approach for the Rapid Identification of Adulterated Water Buffalo Mozzarellas.

Adulteration of Mozzarella di Bufala Campana with cow milk is a common fraud because of the high price and limited seasonal availability of water buffalo milk. To identify such adulteration, this work proposes a novel approach based on the use of species-specific, low-molecular-weight biomarkers (LMWBs). Liquid chromatography-tandem mass spectrometry screening analyses identified ß-carotene, lutein, and ß-cryptoxanthin as LMWBs of cow milk, while ergocalciferol was found only in water buffalo milk. Adulterated mozzarellas were prepared in the laboratory and analyzed for the four biomarkers. Combined quantification of ß-carotene and ergocalciferol enabled the detection of cow milk with a sensitivity threshold of 5% (w/w). The method was further tested by analyzing a certificated water buffalo mozzarella and several commercial products. This approach is alternative to conventional proteomic and genomic methods and is advantageous for routine operations as a result of its simplicity, speed, and low cost.

New Ether-functionalized Morpholinium- and Piperidinium-based Ionic Liquids as Electrolyte Components in Lithium and Lithium-Ion Batteries.

Here, two ionic liquids, N-ethoxyethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide (M1,2O2 TFSI) and N-ethoxyethyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide (P1,2O2 TFSI) were synthesized and compared. Fundamental relevant properties, such as thermal and electrochemical stability, density, and ionic conductivity were analyzed to evaluate the effects caused by the presence of the ether bond in the side chain and/or in the organic cation ring. Upon lithium salt addition, two electrolytes suitable for lithium batteries applications were found. Higher conducting properties of the piperidinium-based electrolyte resulted in enhanced cycling performances when tested with LiFePO4 (LFP) cathode in lithium cells. When mixing the P1,2O2 TFSI/LiTFSI electrolyte with a tailored alkyl carbonate mixture, the cycling performance of both Li and Li-ion cells greatly improved, with prolonged cyclability delivering very stable capacity values, as high as the theoretical one in the case of Li/LFP cell configurations.

Stabilizing the Performance of High-Capacity Sulfur Composite Electrodes by a New Gel Polymer Electrolyte Configuration.

Increased pollution and the resulting increase in global warming are drawing attention to boosting the use of renewable energy sources such as solar or wind. However, the production of energy from most renewable sources is intermittent and thus relies on the availability of electrical energy-storage systems with high capacity and at competitive cost. Lithium-sulfur batteries are among the most promising technologies in this respect due to a very high theoretical energy density (1675 mAh g-1 ) and that the active material, sulfur, is abundant and inexpensive. However, a so far limited practical energy density, life time, and the scaleup of materials and production processes prevent their introduction into commercial applications. In this work, we report on a simple strategy to address these issues by using a new gel polymer electrolyte (GPE) that enables stable performance close to the theoretical capacity of a low cost sulfur-carbon composite with high loading of active material, that is, 70 % sulfur. We show that the GPE prevents sulfur dissolution and reduces migration of polysulfide species to the anode. This functional mechanism of the GPE membranes is revealed by investigating both its morphology and the Li-anode/GPE interface at various states of discharge/charge using Raman spectroscopy.

Enhancing methane production from food waste fermentate using biochar: the added value of electrochemical testing in pre-selecting the most effective type of biochar.

BACKGROUND: Recent studies have suggested that addition of electrically conductive biochar particles is an effective strategy to improve the methanogenic conversion of waste organic substrates, by promoting syntrophic associations between acetogenic and methanogenic organisms based on interspecies electron transfer processes. However, the underlying fundamentals of the process are still largely speculative and, therefore, a priori identification, screening, and even design of suitable biochar materials for a given biotechnological process are not yet possible. RESULTS: Here, three charcoal-like products (i.e., biochars) obtained from the pyrolysis of different lignocellulosic materials, (i.e., wheat bran pellets, coppiced woodlands, and orchard pruning) were tested for their capacity to enhance methane production from a food waste fermentate. In all biochar-supplemented (25 g/L) batch experiments, the complete methanogenic conversion of fermentate volatile fatty acids proceeded at a rate that was up to 5 times higher than that observed in the unamended (or sand-supplemented) controls. Fluorescent in situ hybridization analysis coupled with confocal laser scanning microscopy revealed an intimate association between archaea and bacteria around the biochar particles and provided a clear indication that biochar also shaped the composition of the microbial consortium. Based on the application of a suite of physico-chemical and electrochemical characterization techniques, we demonstrated that the positive effect of biochar is directly related to the electron-donating capacity (EDC) of the material, but is independent of its bulk electrical conductivity and specific surface area. The latter properties were all previously hypothesized to play a major role in the biochar-mediated interspecies electron transfer process in methanogenic consortia. CONCLUSIONS: Collectively, these results of this study suggest that for biochar addition in anaerobic digester operation, the screening and identification of the most suitable biochar material should be based on EDC determination, via simple electrochemical tests.

Structural and Spectroscopic Characterization of A Nanosized Sulfated TiO2 Filler and of Nanocomposite Nafion Membranes.

A large number of nano-sized oxides have been studied in the literature as fillers for polymeric membranes, such as Nafion®. Superacidic sulfated oxides have been proposed and characterized. Once incorporated into polymer matrices, their beneficial effect on peculiar membrane properties has been demonstrated. The alteration of physical-chemical properties of composite membranes has roots in the intermolecular interaction between the inorganic filler surface groups and the polymer chains. In the attempt to tackle this fundamental issue, here we discuss, by a multi-technique approach, the properties of a nanosized sulfated titania material as a candidate filler for Nafion membranes. The results of a systematic study carried out by synchrotron X-ray diffraction, transmission electron microscopy, thermogravimetry, Raman and infrared spectroscopies are presented and discussed to get novel insights about the structural features, molecular properties, and morphological characteristics of sulphated TiO2 nanopowders and composite Nafion membranes containing different amount of sulfated TiO2 nanoparticles (2%, 5%, 7% w/w).

Synthesis and Characterization of Cellulose-Based Hydrogels to Be Used as Gel Electrolytes.

Cellulose-based hydrogels, obtained by tuned, low-cost synthetic routes, are proposed as convenient gel electrolyte membranes. Hydrogels have been prepared from different types of cellulose by optimized solubilization and crosslinking steps. The obtained gel membranes have been characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic-extensional properties, respectively. Hydrogels liquid uptake capability and ionic conductivity, derived from absorption of aqueous electrolytic solutions, have been evaluated, to assess the successful applicability of the proposed membranes as gel electrolytes for electrochemical devices. To this purpose, the redox behavior of electroactive species entrapped into the hydrogels has been investigated by cyclic voltammetry tests, revealing very high reversibility and ion diffusivity.

Preparation and Characterization of Nanocomposite Polymer Membranes Containing Functionalized SnO2 Additives.

In the research of new nanocomposite proton-conducting membranes, SnO2 ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological characteristics, as well as surface and bulk properties of the obtained oxide powders, have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopies, N2 adsorption, and thermal gravimetric analysis (TGA). In addition, dynamic mechanical analysis (DMA), atomic force microscopy (AFM), thermal investigations, water uptake (WU) measurements, and ionic exchange capacity (IEC) tests have been used as characterization tools for the nanocomposite membranes. The nature of the tin oxide precursor, as well as the synthesis procedure, were found to play an important role in determining the morphology and the particle size distribution of the ceramic powder, this affecting the effective functionalization of the oxides. The incorporation of such particles, having sulphate groups on their surface, altered some peculiar properties of the resulting composite membrane, such as water content, thermo-mechanical, and morphological characteristics.

Composite poly(ethylene oxide) electrolytes plasticized by N-alkyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide for lithium batteries.

We report a new class of quaternary polymer electrolyte membranes that comprise poly(ethylene oxide) (PEO), lithium trifluoromethanesulfonylimide (LiTFSI), N-alkyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PyrA,4 TFSI) as an ionic liquid, and a SiO2 filler. The results of differential scanning calorimetry indicate that the addition of SiO2 and different ionic liquids induces a decrease in the PEO melting enthalpy, which thereby increases the ionic conductivity and the Li transference number. The electrochemical stability is proved by using impedance spectroscopy and cyclic voltammetry. Galvanostatic cycling of Li/LiFePO4 cells, which comprise the quaternary polymer electrolytes, revealed their superior performance compared to conventional PEO-Li salt electrolytes. In the course of this investigation, a synergistic effect of the combined ionic liquid-ceramic filler modification could be proved at temperatures close to 50 °C.

Composite Nafion/sulfonated zirconia membranes: effect of the filler surface properties on proton transport characteristics.

Due to their strong acidity and water affinity, sulfated zirconia nanoparticles were evaluated as inorganic additives in the formation of composite Nafion-based membranes. Two types of sulfated zirconia were obtained according to the preparation experimental conditions. Sulfated zirconia-doped Nafion membranes were prepared by a casting procedure. The properties of the composite membranes were compared with those of an unfilled Nafion membrane obtained by the same preparation method. The water uptake, measured at room temperature in a wide relative humidity range, was higher for the composite membranes, this confirming the hydrophilic nature of the selected additives. The membrane doped by zirconia particles having the highest sulphate group concentration showed the highest water diffusion coefficient in the whole range of temperature and relative humidity investigated due to the presence of SO(4) (2-) providing extra acid sites for water diffusion. The proton diffusivity calculated from impedance spectroscopy measurements was compared with water self diffusion coefficients measured by NMR Spectroscopy. The difference between proton and water diffusivity became significant only at high humidification levels, highlighting the role of water in the intermolecular proton transfer mechanism. Finally, great improvements were found when using the composite membrane as electrolyte in a fuel cell working at very low relative humidity.