NH2 Functional Groups Research Articles

Effect of pre-pyrolysis mode on simultaneous introduction of nitrogen/oxygen-containing functional groups into the structure of bagasse-based mesoporous carbon and its influence on Cu(II) adsorption

A convenient effective microwave pre-pyrolysis treatment to synthesize biomass-based mesoporous carbon with higher nitrogen/oxygen-chelating adsorption for Cu(II) is reported here, in which phosphoric acid impregnated bagasse was used as a microwave absorber and porogen. For comparison, conventional electric-heating pyrolyzed carbon was prepared and doped with nitrogen/oxygen groups. Nitrogen adsorption, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and batch adsorption were employed to investigate the effects of the two pre-pyrolysis modes on the sample physicochemical and Cu(II) adsorptive properties. The 22-min-microwave-pyrolyzed bagasse mesoporous activated carbon (MBAC, 85.32% mesoporosity) contained 10.52% O, which is 3.94% more than electric-heating pyrolyzed mesoporous activated carbon (89.52% mesoporosity). After electrophilic aromatic substitutions of N/O doping, the former possessed more N (5.83%) and more O (21.40%), confirming that time-saving energy-efficient microwave pyrolysis favors the formation of defective C/O atoms in or at the edges of the graphite layer of MBAC, which are highly active and tend to act as preferred reactive positions for the doping of N/O-containing groups simultaneously compared with conventional electric-heating pyrolysis. These N and O species existed mainly as COOH, OH, NH and NH2 functional groups, and were confirmed by XPS to be active sites for metal binding via electrostatic attraction, hydrogen bonding, a chelate effect and complexation, resulting in the great enhancement of Cu(II) adsorption. Langmuir isotherm and pseudo-second-order kinetic fitting further proved that Cu(II) adsorption by N/O-doped MBAC is ascribed mainly to chemisorption. Therefore, rapid microwave pre-pyrolysis provides a promising route to prepare excellent-performance N/O-doped carbon adsorbents.

Co-pyrolysis and co-hydrothermal liquefaction of seaweeds and rice husk: Comparative study towards enhanced biofuel production

The production of bio-oil and bio-char by fast pyrolysis and hydrothermal liquefaction of Enteromorpha clathrata, rice husk and their mixtures have been compared. The results indicated that hydrothermal liquefaction produced higher yield of bio-oil and lower yield of bio-char for the same raw samples. There were more macromolecules (hexadecanoic acid, cyclopenten and esters), small-molecule hydrocarbons and N-containing compounds in hydrothermal liquefaction bio-oil, while more aromatic substances were observed in fast pyrolysis bio-oils. There was significant difference between E. clathrata bio-oils from these two thermochemical methods CO, CH/CH2/CH3 and NH functional groups in E. clathrata bio-oil from hydrothermal liquefaction showed stronger absorption strength than bio-oil from fast pyrolysis. However, the only difference between rice husk bio-oil from hydrothermal liquefaction and fast pyrolysis was aromatic ring signal in Fourier transform infrared spectroscopy curves. In addition, synergistic effect was investigated during the co-pyrolysis and co-hydrothermal processes. Such synergistic effect led to the improvement recorded in the bio-oil quality by deoxidation reaction to increase the H/C ratio in bio-oil from co-pyrolysis of E. clathrata/rice husk blends, and reduces the O/C ratio in bio-oil from co-hydrothermal process, and also enhances the calorie value of bio-oil. The synergistic effect, however, lowered the co-pyrolysis and co-hydrothermal bio-oils yields. Moreover, the addition of rice husk into E. clathrata promoted the bio-oil conversion efficiency of protein and increased the content of aromatic substances.

Influence of 6-phenyl-3(2H)-pyridazinone and 3-chloro-6-phenylpyrazine on mild steel corrosion in 0.5 M HCl medium: Experimental and theoretical studies

Two pyridazine derivatives, namely, 6-phenyl-3(2H)-pyridazinone (P1) and 3-chloro-6-phenylpyrazine (P2) were investigated for their influence on mild steel corrosion in 0.5 M HCl, using Tafel polarization, electrochemical impedance spectroscopy (EIS), surface morphology, FTIR and UV–vis techniques. Quantum chemical calculations were also conducted to corroborate experimental findings. P1 was found to accelerate corrosion at low concentrations but exhibits inhibitive action at higher concentrations, attaining 61% inhibition efficiency at 1.25 mM. The inhibitive action of P2 increases with increasing concentration from 88% at 0.1 mM to 96% at 1.25 mM as deduced from EIS measurements. Both compounds are mixed type inhibitors. P2 seems to display chiefly anodic inhibitive effects. The adsorption of P2 on mild steel surface obeys the Langmuir adsorption isotherm and involved competitive physisorption and chemisorption mechanisms. Scanning electron microscopy analyses of steel surfaces in acid-inhibitor solutions showed that both compounds protect mild steel surface effectively at 1.25 mM. FTIR and UV–vis spectroscopic analyses revealed that NH, CO, and CN functional groups of the pyridazine derivatives are actively involved in adsorption of the molecules onto steel surface. Quantum chemical parameters showed that the higher inhibition efficiency of P2 compared to P1 might be related to better electron acceptance ability of P2.

DISCRIMINANT ANALYSIS OF SHODHANA (PROCESSING) ON BALIOSPERMUM MONTANUM MUELL (DANTI) ROOT SAMPLES BASED ON NEAR INFRARED SPECTROSCOPY AND MULTIVARIATE CHEMOMETRIC TECHNIQUE

Objective: To establish a noticeable and a justifiable identification system to assess the impact of shodhana (processing) on various levels of Baliospermum montanum (Danti) root samples obtained through shodhana (processing technique) in quality agreement based on near-infrared-spectroscopy.Methods: Authenticated raw Danti (R. D) root and various Danti root samples obtained after shodhana (processing) such as water processed Danti root (WPDR), Kusha processed Danti root (KPDR) and classical processed Danti root (CPDR), were dried, pulverized and shifted through eighty meshes. The samples were subjected to NIR spectral detection from 750 to 2500 nm at the interval of 1 nm. The multivariate analysis, principal component analysis (PCA) and hierarchical cluster analysis (HCA) analyzed with the help of Unscrambler and Matlab software.Results: Direct spectral analysis indicated the existence of significant numerical and graphical differences between Danti root samples containing different treatments during processing in respect to CH, OH and NH functional groups. The multivariate PCA algorithom plot allowed a clear segregation of the Danti root samples after various data preprocessing technique onto the hotelling T2 95% confidence limit for principal component 1 and 2. The cluster analysis had shown the extra information on the metabolite profiling of the complex purificatory environment. Conclusion: The present study demonstrates a generic, non-destructive solution to discriminate qualitatively in the sample matrix all the differently pretreated samples in favor of the NIR-sensitive functional group.

Feasibility Study of Biosensors Based on Polymelamine‐modified Screen‐printed Carbon Electrodes

AbstractWe herein report the use of melamine and a low‐cost screen‐printed carbon electrode (SPCE) as the base matrices for the preparation of an electrochemical biosensor. Following the electrochemical polymerization of melamine, the resulting polymelamine was deposited on the SPCE surface to give layers bearing –NH2 functional groups, which allowed the attachment of anti‐IgE (immunoglobulin E) antibodies. The resulting anti‐IgE‐labeled SPCEs were then incubated with IgE solutions of various concentrations prior to analysis by chronoamperometry using Ru(NH3)63+ as an electrochemical mediator. A logarithmic relationship was observed between the chronoamperometric current and the IgE concentration between 5.3 and 530 fM (i. e. over 2 orders of magnitude). In addition, a detection limit of 0.64 fM was achieved in addition to a recovery of 114 ± 14 % for a fetal bovine serum sample spiked with 16 fM IgE. Furthermore, only a small quantity of sample was required for analysis, and the IgE assay was suitable for use in a complex serum matrix without interference. We therefore expect that this novel system will be useful for monitoring the changes in blood IgE levels during the clinical treatment of allergic asthma and rhinitis.

A nanohybrid of organoplatinum(II) complex and graphene oxide as catalyst for reduction of p-nitrophenol

In this study, a organoplatinum(II) complex, [Pt(ppy)Cl(dmso)], dmso = dimethylsulfoxide and ppy = deprotonated 2-phenylpyridine, has been covalently immobilized on the graphene oxide (GO) surface through coordination interaction with 3-(aminomethyl)pyridine (3-ampy) ligand spacers (3-ampy-GO), which was synthesized through covalent bonds between NH2 functional groups of 3-ampy and the epoxy groups of GO. The synthesis of Pt(0)/3-ampy- reduced-graphene oxide (RGO) nanohybrid by the reduction of [Pt(ppy)Cl(3-ampy)]/GO nanohybrid with hydrazine in an aqueous solution was studied. Nanohybrids were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). Catalytic activities of these nanohybrids were investigated in the p-nitrophenol reduction. On the basis of comparative kinetic studies, the following trend was obtained for the effect of the related nanohybrid catalyst on the rate of reaction: [Pt(ppy)Cl(3-ampy)]/GO > Pt(0)/3-ampy-RGO.

Base Layer Influence on Protonated Aminosilane Gradient Wettability.

Protonated amine gradients have been prepared on silicon wafers via programmed controlled rate infusion (CRI) with varying degrees of hydrophobicity and characterized by X-ray photoelectron spectroscopy (XPS) and static and Wilhelmy plate dynamic contact angle measurements. Initially, base layers were spin coated from sols containing tetramethoxysilane (TMOS) and either phenyltrimethoxysilane (PTMOS), dimethyldimethoxysilane (DMDMOS), or octyltrimethoxysilane (OTMOS, C8). Amine gradients were then prepared from 3-aminopropyltriethoxysilane (APTEOS) via CRI. Gradients were exposed to concentrated HCl vapor for amine protonation. XPS showed that NH2 functional groups were distributed in a gradient fashion as a result of CRI controlling the time of exposure to APTEOS. Interestingly, the overall extent of N modification depended on the type of base layer used for gradient formation. The C8-derived base layer had about half the amount of nitrogen on the surface as compared to those prepared from TMOS, which was attributed to a reduction in the number and accessibility of surface silanol groups. The wettability and contact angle (CA) hysteresis were also dependent on the base layer and varied along the length of the gradient. The greatest CA change across the length of the gradient was observed on the gradient formed on the C8-derived base layer. Likewise, the CA hysteresis was approximately 2 times larger on the C8-modified surfaces, indicative of greater chemical inhomogeneity. In contrast to uniformly modified substrates, Wilhelmy plate CA analysis that involves the immersion of samples gave a unique S-shaped CA distance curve for the gradients. The three curve segments correspond to hydrophilic, hydrophobic, and a middle connecting region. Importantly, these curves give precise CAs along the gradient that reflect the surface chemistry and coverage defined by programmed CRI processing.

Removal of U(VI) from Aqueous Solution by Amino Functionalized Flake Graphite Prepared by Plasma Treatment

Flake graphite (FG) with high uranium(VI) entrapment efficiency was successfully fabricated via a simple and efficient nonthermal plasma treatment method. FG was modified with −NH2 functional groups through nonthermal plasma with different treatment times under vacuum conditions. The modified FG samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR spectra), thermogravimetric analysis (TGA), BET surface area measurements, and zeta potential. FG samples with different treatment times are used as contrast adsorbents for U(VI) entrapment. The adsorption experiments show that the modified FG has higher high U(VI) entrapment efficiency than others, and longer treatment time results in higher efficiency, demonstrating that the plasma treatment can greatly increase the active sites of FG samples and lead to the successful grafting of −NH2 on FG surface. The −NH2 modified FG with 2 h treatment time shows the highe...

Synergistic interaction of Re complex and amine functionalized multiple ligands in metal-organic frameworks for conversion of carbon dioxide

A metal-organic framework (MOF) is composed of secondary building units (SBUs) of metal ions and organic ligands to link each SBU. Moreover, the photosynthetic synthesis of a valuable CO chemical from carbon dioxide (CO2) represents an important class of appealing methods. Herein, we find that a molecular photocatalyst with high selectivity and activity can be designed via a fine balance in the proximity of Re complex (ReI(CO)3(BPYDC)(Cl), BPYDC = 2,2′-bipyridine-5,5′-dicarboxylate) and -NH2 functionalized multiple ligands composing a MOF photocatalyst, denoted as Re-MOF-NH2. These ligands in Re-MOF-NH2 has been confirmed by infrared, UV-visible, and 1H nuclear magnetic resonance spectra. Moreover, we show from extended X-ray absorption fine structure and in-situ infrared spectra that the bond corresponding to Re-CO upon introduction of -NH2 functional groups is divided into asymmetric bonds of 1.4 Å and 2.3 Å along with different CO2 vibrations, thus making the configuration of carbonyl groups in a Re metal complex become asymmetric in addition to aiding formation of CO2 intermediates within Re-MOF-NH2. Indeed, both of the uneven electron distribution in asymmetric carbonyl groups for Re-CO and the intermolecular stabilization of carbamate intermediates are proven to give the approximately 3-fold increase in photocatalytic activity for conversion of CO2 into CO.

Synthesis of poly(o -phenylenediamine) nanofiber with novel structure and properties

The poly(o-phenylenediamine) (PoPD) was synthesized from the monomer o-phenylenediamine in various organic solvent medium viz. dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF) and methanol using ammonium per sulfate as a radical initiator. The structure just like polyaniline derivative with free NH functional groups of the synthesized polymers confirmed by various standard characterizations was explained from the proposed polymerization mechanism. All the synthesized polymers were completely soluble in common organic solvent like DMSO and DMF because of the presence of polar free NH functional groups in its structure. The formation of polymer nanofiber by reverse salting-out process was confirmed, and the synthesized polymer in DMSO medium was the best polymer in terms of nano-morphology as well as conducting properties. Interestingly, the average DC conductivity of undoped polymer film was recorded as 2.21 × 10−6 Scm−1 because of induced doping through self charge separation. Moreover, the conductivity of the polymer film was further increased to 1.16 × 10−3 Scm−1 after doping by sulfuric acid. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of structure of poly(o-phenylenediamine) on the doping ability and conducting property

Poly(o-phenylenediamine) with ladder-type structure was formed in aqueous hydrochloric acid medium below pH 1, while open ring-type amine derivative, i.e., −NH2 functional group substitution of polyaniline structure, was obtained in 1:1 aqueous sulfuric acid medium from the chemical synthesis of the monomer o-phenylenediamine. However, poly(o-phenylenediamine) having structure like polyaniline derivative with free =NH functional groups was obtained by chemical synthesis in dimethyl sulfoxide medium. The ladder-type polymer was almost insoluble but the other two types of synthesized polymers having polar functional group substitutions were well soluble in polar organic solvent like dimethyl sulfoxide, N,N-dimethyl formamide, and tetrahydrofuran. The freestanding films were cast from dimethyl sulfoxide solution of both the soluble functional polymers. The polymers having different structures were doped with inorganic acid by solution doping technique and the doped polymers were characterized by various standard characterizations. In order to explore the electronic uses of the polymers like sensor and actuators, the influences of their structure on the doping ability as well as ionic properties of the sulfuric acid-doped polymers were compared.

Room temperature synthesis of TiO2 supported chitosan photocatalyst: Study on physicochemical and adsorption photo-decolorization properties

The room temperature in-situ sol gel technique was used to synthesize TiO2 supported chitosan (CS) nanocomposites. The effect of calcination was assessed in the context of its physicochemical and adsorption-photodecolorization properties. During sol gel, hydrolysis and condensation of titanium alkoxide was conducted under acidic conditions, which resulted in the formation of crystalline anatase phase in TiO2-CS (TC) composite at room temperature. Furthermore, calcination treatments (100°C, 300°C, 500°C) gradually increased the charge carrier recombination rates, due to the thermal degradation of Chitosan. Photocatalytic activity was assessed using Methyl orange, which resulted in 100% decolorization within 90min of UV exposure with un-calcined nanocomposite. Hence, the reactive OH and NH2 functional groups on the surface of CS are responsible for the adsorption-photodecolorization process. Overall, this study provides comprehensive data on the effective modification of TiO2 with Chitosan and the effect of calcination on the physicochemical and adsorption-photodecolorization properties of the TC nanocomposite.

Mechanical properties of nanocomposites with functionalized graphene

The research investigated the thermal and mechanical properties of graphene/epoxy nanocomposites. Pristine graphene and functionalized graphene were used as nano-reinforcement in the nanocomposites. The graphene loadings employed in the nanocomposites were 0.1, 0.3, 0.5, and 1.0 wt%. The functional groups grafted on the functionalized graphene were characterized through Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Results indicated that two kinds of functional groups are grafted on the functionalized graphene surfaces: one contains only COOH group and the other contains both COOH and NH2 groups. Moreover, from mechanical and thermal testing, it was found that the nanocomposites with functionalized graphene demonstrate better mechanical and thermal properties than those with pristine graphene. The graphene containing NH2 and COOH functional groups exhibits superior mechanical and thermal properties than the graphene with only COOH functional group. In addition, Young’s modulus and thermal conductivity of the nanocomposites increase as the graphene loading increases. However, the fracture toughness and tensile strength of the nanocomposites attain peak values when the functionalized graphene loading is 0.1 wt%. The effects of the functional groups on the mechanical and thermal properties of nanocomposites were elaborated using molecular dynamics (MD) simulation. It was revealed that the interfacial thermal conductance and normalized interaction energy increase between the functionalized graphene and epoxy matrix, which may be responsible for the enhanced mechanical properties in the functionalized graphene/epoxy nanocomposites.

Dual-end-functionalized tin (Sn)-phyllosilicates for the esterification of oleic acid

We designed dual-end-functionalized tin (Sn)-phyllosilicate, where the SH functional groups were subsequently oxidized for SO3H/SO4H functionalities in a Brønsted acid with/without NH2 functional groups in a Brønsted base. Dual-end-functionalized tin (Sn)-phyllosilicates [MTES:APTS=1.0:0.11, MTES:TEOS=1.0:0.11 and 1.0:0.43, v/v] were fabricated where the inorganic framework of Sn species can function as a Lewis acid. The Sn-phyllosilicates with dual acids were applied to esterify oleic acid and produce oleic acid-methyl-ester to test their feasibility as fatty-acid-conversion solid catalysts. In the absence of amine groups, the increase in ratio of tetraethyl orthosilicate (TEOS) to (3-mercaptopropyl)trimethoxysilane (MTES) for the synthesis of Sn-phyllosilicates (MTES:TEOS=1.0:0.11 and 1.0:0.43, v/v) increased the recovery of Sn-phyllosilicate in the solvent media and gradually decreased the oleic acid-methyl-ester production efficiency (%) of the oleic acid conversion. At the fixed 2.0wt% Sn-phyllosilicate (MTES:APTS=1.0:0.11, v/v) loading and oleic acid:MeOH weight ratio=1:1, an 80°C reaction temperature and 4h reaction time were determined to be the optimal conditions for the oleic acid-methyl-ester production, which had ∼90% oleic acid conversion efficiency. When the Sn-phyllosilicate (MTES:APTS=1.0:0.11, v/v) loading was increased from 0.1 to 5.0wt% at 80°C and 4h, the fatty-acid conversion efficiency (%) of oleic acid gradually increased from 39.16 to 92.23%. In contrast, Sn-phyllosilicate (MTES:TEOS=1.0:0.43) had the lowest oleic acid conversion efficiency (%) but the highest catalyst recovery. In summary, this study presents a facile method to produce oleic acid conversion catalysts on an industrial scale.

Nonlinear Optical (NLO) Response of Pristine and Functionalized Dodecadehydrotribenzo[18]annulene ([18]DBA): A Theoretical Study

Abstract The structural, electronic, and nonlinear optical (NLO) properties of pristine dodecadehydrotribenzo[18]annulene ([18]DBA) functionalizing with the alkali metal atom (Li and Na), NH2 and NO2 functional groups and its location are inspected through density functional theory (DFT) calculations. The NBO analysis indicates that functionalizing [18]DBA caused increasing charge transfer (CT) and introduced a new acceptor–donor model for NLO materials due to the structure with of π-electron of [18]DBA. The results demonstrate that the functional groups notably narrow the energy gap of [18]DBA, and the electronic character of [18]DBA is sensitive to the functional groups. Furthermore the considered functional groups enhance the static first and second hyperpolarizability of [18]DBA. Interestingly, replacement of H atom by Na and NO2 in [18]DBA leads to large static first hyperpolarizability (β0) values of 3977.40 and 3722.56 au and very great static second hyperpolarizability (γtot) 980380.40 and 752886.20 au, respectively, which is the largest among the considered functionalizing structures. Also transition energies (ΔE) decrease due to functionalizing, and the best location for functionalizing is position 2.

TiO2/titanate composite nanorod obtained from various alkali solutions as CO2 sorbents from exhaust gases

A series of TiO2/titanate composite nanorods-based CO2 adsorbents with a high capture efficiency was prepared through hydrothermal method, followed by annealing at 350 °C in air, and subsequent functionalization with tetraethylenepentamine (TEPA). The CO2 adsorption performance of the prepared samples was measured using TGA. Firstly, it was found that the increase of adsorption capacity was related to textural properties of tested nanomaterials (higher for nanorod composites than for starting TiO2 and P25 powders). Secondly, the TiO2/titanate composite nanorods, obtained in the presence of KOH, exhibited higher adsorption capacity for CO2 in comparison with the NaOH-modified samples due to the increase of the SBET, total mesopore volume. Moreover, the nanorod composites obtained in presence of KOH exhibited a high content of titanate. TEPA-modified TiO2/titanate composite nanorods (P25-NRsK-TEPA) showed the highest adsorption capacity of 3.02 mmol CO2/g. This result could be indirectly related to high surface area responsible for maximizing exposure of its NH2 functional groups for interaction with CO2 and the higher pore volume, which may reduce the conglomerates of the impregnated TEPA within the pores, leading to better distribution of amine and consequently increasing the CO2 adsorption capacity. The results also indicates that TEPA-titanate interaction enhances CO2 capacity compared to TEPA-anatase materials. That material not only displayed high CO2 adsorption capacity but also exhibited a relatively stable performance during 6 consecutive adsorption-desorption cycles.

Quartz Crystal Microbalance Technique for in Situ Analysis of Supersaturation in Cooling Crystallization.

A quartz crystal microbalance (QCM) is used as a novel in situ strategy for analyzing the supersaturation profile during cooling crystallization. The main concept is based on preventing any solid mass loading on the QCM sensor by modifying the sensor surface. As a result, the QCM responses only depend on the solution concentration changes during the crystallization. The proposed strategy is confirmed on the basis of an analysis of sulfamerazine (SMZ) crystallization. When the QCM sensor is modified using 11-amino-1-undecanethiol (AUT), crystal formation on the sensor is completely prevented due to a repulsive interaction between the -NH2 functional groups of the AUT and SMZ crystals. Thus, the QCM responses reflect only the property changes in the solution phase during the crystallization. The supersaturation in the solution is then estimated on the basis of the difference in the frequency shifts between the SMZ solution and a blank solution. The accuracy of the in situ QCM analysis of supersaturation is confirmed using an off-line gravimetric method.

Ammonia-based plasma treatment of single-walled carbon nanotube thin films for bio-immobilization

The bio-immobilization efficiency of single-walled carbon nanotube (SWCNT) thin films treated in NH3/Ar/N2 inductively coupled plasmas with different Ar/N2 gas mixing ratios was studied. The plasma parameters as well as the densities and fluxes of the plasma active species were controlled using both plasma diagnostics (Langmuir probes, optical emission spectroscopy) and modeling. The surface morphology of the SWCNT thin films was observed by field-emission scanning electron microscopy (FE-SEM). The structural changes on the treated surfaces were detected by Raman spectroscopy. The changes in atomic composition for plasma-treated and pristine SWCNT film surfaces were analyzed by X-ray photoelectron spectroscopy (XPS). Fluorescence analysis of the plasma-functionalized SWCNT surfaces was performed with green fluorescent proteins (GFPs). It was found that the transition from NH3/Ar to NH3/N2 gas system at other constant processing conditions resulted in increasing the CNT surface roughness, the degree of structural defects, the number of NH2-functional groups connected to the CNT surface and the bio-immobilization capability. It was proposed that all these effects are connected to the chemical etching and modification of SWCNTs due to the increased flux of NHx (x < 3) species.

Effect of different additives with –NH2 or –NH4+ functional groups on V(V) electrolytes for a vanadium redox flow battery

Several organic amines with –NH2 functional groups and inorganic ammoniums with –NH4+ functional groups have been comparatively investigated as stabilizers of the V(V) electrolyte for vanadium redox flow battery (VRB) to improve its stability and electrochemical performance. Thermal stability tests showed that chitosan (CTS) and nonionic-type polyacrylamide (NPAM) additives with –NH2; ammonium thiocyanate (ATC), ferrous ammonium sulfate (FAS) and ammonium ferric sulfate (AFS) additives with –NH4+ could significantly improve the thermal stability of the V(V) electrolyte over a wide temperature range of −5°C to 45°C. The electrochemical behavior of the V(V) electrolyte with these preferred additives was further studied by cyclic voltammetry (CV), steady state polarization, electrochemical impedance spectroscopy (EIS) and charge–discharge test. The results indicated that the electrochemical activity and reversibility for the V(V) electrolyte with the best additive CTS with –NH4+ was significantly improved compared with the additives with –NH2 and pristine one. In addition, the VRB employing the positive electrolyte with CTS exhibited excellent cycling stability and charge–discharge behavior with a high energy efficiency of 82.5%. The N-containing and O-containing functional groups of CTS in the V(V) electrolyte could modify the electrode and further improve the electrochemical performance and cycling stability of VRB.

Composite membranes of chitosan and titania‐coated carbon nanotubes as promising materials for new proton‐exchange membranes

ABSTRACTTitania‐coated carbon nanotubes (TCNTs) were obtained by a simple sol–gel method. Then chitosan/TCNT (CS/TCNT) composite membranes were prepared by stirring chitosan/acetic acid and a TCNT/ethanol suspension. The morphology, thermal and oxidative stabilities, water uptake and proton conductivity, and mechanical properties of CS/TCNT composite membranes were investigated. The CNTs coated with an insulated and hydrophilic titania layer eliminated the risk of electronic short‐circuiting. Moreover, the titania layer enhanced the interaction between TCNTs and chitosan to ensure the homogenous dispersion of TCNTs in the chitosan matrix. The water uptake of CS/TCNT composite membranes was reduced owing to the decrease of the effective number of the NH2 functional groups of chitosan. However, the CS/TCNT composite membranes exhibited better performance than a pure CS membrane in thermal and oxidative stability, proton conductivity, and mechanical properties. These results suggest that CS/TCNT composite membranes are promising materials for new proton‐exchange membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43365.