•Uniform NiHCF nanocubes are successfully fabricated on flexible carbon fibers by UPED method.•NiHCF nanocubes based electrode exhibits remarkable specific capacitance in neutral electrolytes.•NiHCF nanocubes based electrode shows excellent charge-discharge cycle stability.•NiHCF nanocubes based flexible electrode has a capacitance as high as 476 Fg−1.To develop a kind of flexible electrode for supercapacitors working in neutral electrolyte, nickel hexacyanoferrate nanocubes (NiHCF-NCs) are uniformly deposited on flexible carbon fibers (CFs) by using a facile unipolar pulse electrodeposition (UPED) technique. It is found that NiHCF film prepared by UPED is composed of NCs with more uniform size than those prepared by the common cyclic voltammetry (CV) and potentiostatic (PM) methods. Pulse potential of UPED has significantly influence on the morphology and crystal structure. Uniform NiHCF-NCs with approximately 200 nm side length are successfully formed on flexible CFs at 0.3 V. Moreover, the ratio of two structures of NiHCF, i.e., “insoluble” and “soluble” structures, can be well controlled by the applied pulse potential. Electrochemical performances are characterized by CV, galvanostatic charge/discharge and electrochemical impedance spectroscopy tests. NiHCF-NCs film on flexible carbon fibers prepared at 0.3 V applied pulse potential exhibits remarkable electrochemical performance with a capacitance as high as 476 F g−1 at 0.2 A g−1 in the neutral electrolyte, and the capacitance retains 92.5% of its initial value after 8000 charge/discharge cycles. It indicates that such a simple, cost-effective and readily scalable NiHCF-NCs film fabrication method has commercial potential for preparation of flexible electrode for high performance supercapacitors working in neutral electrolyte.

ABSTRACTPoly(siloxane-ether-urethane)-acrylic (PU-AC) hybrid emulsions were prepared by introducing different hydroxyethoxypropyl-terminated polydimethylsiloxane (PDMS) content into the acrylic-terminated poly(ether-urethane) backbone and then in situ copolymerizing with methyl methacrylate and butyl acrylate via emulsion process. The effects of PDMS on the particle size and viscoelastic behavior of the hybrid emulsions were investigated. Meanwhile, the hydrogen bonding, mechanical and thermal mechanical properties, water resistance, the surface gloss, and wettability of the resultant hybrid films were also studied. The results showed that all the hybrid emulsions showed shear-thinning behaviors, and the introduction of PDMS resulted in the formation of the hybrid emulsions with increased average particle size and decreased viscosity. The chemical bonds built between PU and AC yielded higher than 73% crosslinking fraction in all the hybrid materials, but this value decreased with increasing PDMS content because PDMS reduced the hydrogen bonding interactions and enhanced the phase separation. As a result, an increase in the PDMS content led to an increase in the elongation, water resistance, surface roughness, and water hydrophobic of the films, but the tensile strength, hardness, storage modulus, and glass transitions temperature decreased. It is suggested that introduction of PDMS can provide the hybrid materials with the improved flexibility, water resistance, and surface hydrophobicity, which has potential application value in the fouling-release coatings, biomaterials, and surface fishing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44927.

•A novel BPEI-CQD/PPy/PSS membrane was successfully synthesised and used for the removal of Cu2+.•Sorption-diffusion model was proposed for the ESIP system.•3D BPEI-CQD/PPy/PSS membrane exhibited excellent permselectivity for Cu2+.•The current efficiency of the ESIP system reached 39.9%.The continuous separation of dilute Cu2+ from wastewater was performed by using a branched poly(ethylenimine) (BPEI)-functionalized carbon quantum dots (BPEI-CQD)/polypyrrole (PPy)/ polystyrenesulfonate (PSS) membrane in an electrochemically switched ion permselective (ESIP) process. The membrane with a high selectivity for Cu2+ separation was prepared by pressure filtering BPEI-CQD/PPy/PSS solution through a polytetrafluoroethylene (PTFE) membrane. In this ESIP system, the directional uptake/release of Cu2+ was realized by modulating the redox state of the membrane coupling with an external electric field. The effects of the operating parameters on the flux of Cu2+ and membrane permselectivity were investigated. The BPEI-CQD/PPy/PSS composite electrode showed excellent permselectivity for Cu2+ with a flux of 0.108 mg·cm−2·h−1, a current efficiency of 39.9% and an excellent cycling stability. The Cu2+ concentration in the solution was reduced from 30 to 0.82 ppm with a removal efficiency of 97.2%. Furthermore, the effects of BPEI-CQD content and the membrane thickness on the separation properties of the membrane from a mixed nitrate solution containing Cu2+, Ni2+ and Cd2+ were investigated. It is expected to understand the sorption-diffusion mechanism of such a membrane and provide more information on the design of it for a practical metal ion separation process.Download high-res image (83KB)Download full-size image

•Electrical double layer ion transport mechanism was proposed for ESIP system.•A novel cell voltage–pulse potential coupling circuit was used in ESIP system.•MWCNT/PTFE membrane had excellent permselectivity for Pb2+.•The high flux of Pb2+ was obtained due to the synergy effect of cell voltage and pulse potential.•The current efficiency of ESIP system reached 46.1%.Continuous separation of dilute Pb2+ from wastewater was demonstrated by using a membrane containing highly conductive multiwalled carbon nanotubes (MWCNTs) in an electrochemically switched ion permselective (ESIP) process, with a cell voltage–pulse potential coupling circuit. The membrane with high selectivity for Pb2+ separation was fabricated by pressure filtering MWCNT solution through a polytetrafluoroethylene (PTFE) film. In the separation system, the directional uptake and release of Pb2+ were realized by modulating the positive and negative charge densities on the electrical double layer (EDL) of the membrane, together with the application of an external electric field. The effects of the operating parameters on the flux of Pb2+ and membrane permselectivity were investigated. The highest Pb2+ flux across the membrane occurred with considerable permselectivity at a cell voltage of 0.8 V, a pulse width of 40 s, and a membrane MWCNT content of 30 mg. The system reduced the Pb2+ concentration in the solution from 30 to 0.36 ppm with a current efficiency of 46.1%. Such a novel EDL membrane-based ESIP system could be used for wastewater treatment.Download high-res image (283KB)Download full-size image

A series of new hydroxypyridine-based ionic liquids (ILs) are synthesized and applied in CO2 capture through chemical absorption, in which one IL, i.e., tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]), shows a viscosity as low as 193 cP with an absorption capacity as high as 1.20 mol CO2 per mol IL. Because the traditional anion–CO2 absorption mechanism cannot provide an explanation for the influences of cations and temperature on CO2 absorption capacity, herein, a novel cation-participating absorption mechanism based on the proton transfer is proposed to explain the high absorption capacity and the existence of a turning point of absorption capacity with the increase of temperature for the capture of CO2 using [P4444][n-Op] (n = 2, 3, 4) ILs. Also, the relationship between the viscosity of ILs and the linear interaction energy is proposed for the first time, which can guide how to design and synthesize ILs with low viscosity. Quantum chemistry calculations, which are based on the comprehensive analysis of dipole moment, cation–anion interaction energy and surface electrostatic potential, indicate that the different viscosities of hydroxypyridine-based ILs and the changes after CO2 absorption mainly resulted from the different distribution of negative charges in the anion.

To achieve low cost, high rate and attractive capacity of CO2 adsorption by using ionic liquids (IL), a new mesostructured ionogel, pyridine-containing anion functionalized IL tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]) encapsulated silica MCM-41 (noted as PM-w), is fabricated by loading the IL [P4444][2-Op] with multiple active sites into porous silica MCM-41 through a simple moisture-controlled impregnation–evaporation method. Allosteric effect driven gas sorption on the electronegative oxygen and nitrogen atoms of the nanoconfined IL [P4444][2-Op] makes it take no more than 2 min for the ionogel PM-5 to achieve the 90% of saturated adsorption capacity. The corresponding adsorption rate is 30 times faster than that of the bulk IL. The ionogel PM-5 with the low IL loading of 5.0% shows the highest CO2 adsorption capacity up to 1.21 mmol (g-ionogel)−1 (14.89 mmol (g-IL)−1) at 50 °C in a gas mixture with N2, which is 9.25 times higher than that of the pure IL. Its excellent cyclic stability of more than 96% of the initial CO2 uptake repeatedly displayed after performing 10 cycles of adsorption–desorption tests. The enhanced thermal stability up to 450 °C in N2 is observed for the low loading ionogels since the strong interfacial layering of the IL prefers to dot the silica nanopores as monomolecular islands. Reversely, the high loading IL may aggregate into nanosized clusters that recover the poor thermal stability of the bulk IL. Reasonable decreases in their surface area, pore volume and pore size are observed with the IL loading up to 45%. They still exhibit highly ordered hexagonal mesostructures. The features of low loading and cost, rapid adsorption, high capacity and excellent cyclic stability make the ionogel PM-5 a competitive candidate in CO2 capture from flue gas.

•The flow pattern in the novel BFB with a continuous feed/discharge was investigated.•The particles motion was simulated with DPM coupled with Eulerian–Eulerian two-fluid model.•Principles of optimizing feeding tube of the BFB were determined.•High solids flux of 1200 kg/m2 s could be achieved in TBCFB gasifier based on the simulation.A bubbling fluidized bed (BFB) with a continuous feed/discharge of solids was used as a gasifier in a high-density triple-bed circulating fluidized bed (TBCFB). To carry the heat from the combustor to the pyrolyzer/gasifier effectively, a high-density and high solids-mass flux circulating system is necessary. In this study, the gas-solid flow behavior of a BFB with high solids continuous feeding/discharging mass flux was simulated by an Eulerian–Eulerian model incorporating the Lagrangian (discrete phase model) properties of particles as a tracer to analyze particle motion and determine the optimal feeding tube location and diameter. It was observed that a U-shaped track of particles from the inlet to the outlet and double vortices resulted in particle back-mixing and extended particle residence time. According to the results, some feeding-tube design principles were proposed to achieve smooth solids flow and improve the particle residence time in the BFB in solids mass circulating fluxes ranging from 800 to 1200 kg/m2 s.Download high-res image (198KB)Download full-size image

•Kinetic parameters of coal pyrolysis were obtained by DAEM via TG/DTG experiments.•E0 = 186.5 kJ/mol, k0 = 3.96 × 1010 s−1 and σ = 39.5 kJ/mol were obtained.•A coal particle pyrolysis model coupling with reaction and heat transfer was proposed.•Mass fraction and temperature profiles inside the coal particle was well predicted.•ΔT > 300 K from surface to core of a 3 mm particle was predicted at 900 °C pyrolysis.A comprehensive and systematic study on the fundamental pyrolysis behaviors of a single coal particle was performed in this study. The pyrolysis characteristics of coal was investigated by non-isothermal thermo gravimetric analysis whereas the reaction kinetic parameters were obtained by using the distribute activation energy model (DAEM). As three heating rate profiles were applied (10, 20 and 30 °C/min) in TG/DTG experiments with a final pyrolysis temperature of 900 °C, the obtained kinetic parameters, i.e., activation energy (E0), pre-exponential factor (k0) and standard deviation (σ) were 186.5 kJ/mol, 3.96 × 1010 s−1 and 39.5 kJ/mol, respectively. When these calculated kinetic parameters were used to predict devolatilization curves, the simulation results were in well agreement with the experimental data. As such, a one-dimensional, time-dependent particle pyrolysis model was proposed to characterize the detailed chemical and physical phenomena occurred within a pyrolyzing coal particle. It is found that this model successfully predicted the mass fraction residue and temperature profiles inside the coal particle. In addition, the effect of particle size on pyrolysis performance was also investigated through simulation. It is expected that such a model can be integrated with CFD simulation to provide useful insight for the design of a practical coal pyrolysis reactor.Download high-res image (299KB)Download full-size image

•ZIF-8/PEBA-2533 MMM was successfully fabricated for phenol permselective pervaporation.•The permeability and permselectivity of PEBA-2533 membrane to phenol were greatly improved.•10 wt% ZIF-8/PEBA-2533 MMM showed the most excellent pervaporation performance.•The PSI value as high as 67.6 kg m−2 h−1 was obtained by 10 wt% ZIF-8/PEBA-2533 MMM.•The separation mechanism of the MMMs was found to be different from that of pure PEBA-2533 one.In recent years, zeolitic imidazolate framework-8 (ZIF-8) has received tremendous attention due to its hydrophobic inner channels and good compatibility with the polymer as an inorganic filler for preparation of the mixed matrix membrane (MMM). In this study, ZIF-8 particles were synthesized and incorporated into Ploy (ether block amide) matrix (PEBA-2533) to fabricate a MMM for the enhancement of phenol permselective pervaporation. The structure and morphology of ZIF-8 particle and the obtained MMMs were characterized by XRD, SEM, FTIR, contact angle and BET. It is found that the hydrophobicity of the membrane was enhanced by the incorporation of hydrophobic ZIF-8, and the obtained MMM withstand the extreme operation conditions of pervaporation. The effects of particle loading amount, feed concentration and temperature on the separation performance of ZIF-8 incorporated MMMs were investigated in details. Compared with the pure PEBA-2533 membrane, the permeate flux of ZIF-8 incorporated PEBA-2533 MMM with a 10 wt% loading amount was significantly increased from 846 g m−2 h−1 to 1310 g m−2 h−1, while the separation factor increased from 39 to 53 at 70 °C with 8000 ppm feed phenol concentration. The enhancement of the pervaporation performance could be mainly attributed to the preferential highly permeable regions of the bimodal membrane structure for phenol molecules, which was consisted of ZIF-8 particles. Finally, both of the excellent overall membrane pervaporation performance and the long-term revealed that such a ZIF-8 incorporated MMM has a great potential in separation and recovery of phenol from its aqueous solution for a practical process.

A three-Gaussian distributed activation energy model (DAEM) reaction model (3-DAEM) was successfully applied for the kinetics study on the thermal pyrolysis of four types of low-rank coals, based on their nonisothermal thermogravimetric data. It is found that 3-DAEM was feasible for the analysis of coal pyrolysis process, which can be divided into three stages, using the second derivative method for thermogravimetry (TG) curves and the Peakfit software for differential thermogravimetry (DTG) curves. Calculated kinetic parameters, including three mean activation energies (E0), three standard deviations (σE), and two weights (w), were used to predict the pyrolysis process, and the results agreed well with the experimental data. Furthermore, the kinetics parameters were found to have a strong relationship with the DTG curve shape and especially with the coal property. These results indicated that 3-DAEM provided a good way to process thermogravimetric analysis (TGA) data and understand the pyrolysis mechanism for low-rank coals.

An in situ potential-enhanced ion transport system based on the electrochemically switched ion permselectivity (ESIP) membrane was developed for the effective removal of Ca2+ and Mg2+ from dilute aqueous solution. In this system, uptake/release of the target ions can be realized by modulating the redox states of the ESIP membrane, and continuously permselective separation of the target ions through the ESIP membrane can be achieved by tactfully applying a pulse potential on the membrane and combining with an external electric field. In this study, iron hexacyanoferrate (FeHCF)–polypyrrole/polystyrenesulfonate (PPy/PSS) ESIP membrane with high conductivity and high flux was prepared by using stainless steel wire mesh (SSWM) as conductive substrate. The driving force for the ion transport was analyzed in detail by the equivalent circuit of the system. It is found that the FeHCF interlayer between the SSWM substrate and the PPy/PSS membrane played an important role in removing Ca2+ and Mg2+ from aqueous solutions, and markedly enhanced the separation performance of the membrane due to the improvement of the electroactivity as well as the change of the surface morphology. Influences of the applied cell voltage of the external electric field and the pulse (constant) potential across the membrane on the separation of Ca2+ and Mg2+ were investigated. It is demonstrated that the pulse potential was more beneficial for improving the removal efficiency than the constant potential applied on the membrane. The hardness of the treated water was reduced to 50 ppm (CaCO3) by applying a pulse potential of ±2.0 V and an cell voltage of 5.0 V when the initial concentration of Ca2+ was 10 mM (1000 ppm (CaCO3)). It is expected that the in situ potential-enhanced ion transport system based on the FeHCF–PPy/PSS membrane could be used as a novel water softening technology.

•NH2-Gs are synthesized from the hydrothermal reaction of GO and ammonia.•NH2-Gs are synthesized with an appropriate amount of amine groups and graphitic C.•A simple method has been developed for the growth of Co3O4/NH2-Gs composites.•Co3O4/NH2-G(2) exhibits the highest capacitive performance.•The strong interaction between Co3O4 and NH2-G(2) ascribed to the high performance.A simple and scalable method has been developed for the growth of Co3O4 on amine modified graphene (NH2-Gs), synthesized from the hydrothermal reaction of graphene oxide in the presence of ammonia. It shows that the relative NH3 content could alter the elemental composition and the relative percentages of functional groups in NH2-Gs, and the Co3O4 particles on the NH2-Gs with a relatively higher amount of amine groups exhibit a relatively small sizes. The obtained Co3O4/NH2-Gs can then be used as an active electrode material for supercapacitors. Among the synthesized samples, Co3O4/NH2-G(2) (the weight ratio of ammonia to GO is 5) exhibits the highest capacitive performance, 2108.4 F g−1 at 1 A g−1 and 1356.7 F g−1 at 15 A g−1, which is much higher than that of Co3O4 based materials reported previously. The electrode also has a satisfactory cycling performance with capacity retention of 64% after 800 cycles at 5 A g−1. The enhanced electrochemical performances of Co3O4/NH2-G(2) are ascribed to the higher specific surface area, the smaller Co3O4 particle sizes, the strong interaction between Co3O4 and NH2-G(2), and the higher conductivity. The excellent electrochemical performance makes the resultant composite materials to be a promising candidate for supercapacitor electrode application.A simple and scalable method has been developed for the growth of Co3O4 on amine modified graphene (NH2-Gs), synthesized from the hydrothermal reaction of graphene oxide in the presence of ammonia. Among the synthesized samples, Co3O4/NH2-G(2) exhibits the highest capacitive performance and a satisfactory cycling performance.

A facile unipolar pulse electropolymerization (UPEP) technique is successfully applied for the preparation of ion-imprinted composite film composed of ferricyanide-embedded conductive polypyrrole (FCN/PPy) for the selective electrochemical removal of heavy metal ions from wastewater. The imprinted heavy metal ions are found to be easily removed in situ from the growing film only by tactfully applying potential oscillation due to the unstable coordination of FCN to the imprinted ions. The obtained Ni2+ ion-imprinted FCN/PPy composite film shows fast uptake/release ability for the removal of Ni2+ ions from aqueous solution, and the adsorption equilibrium time is less than 50 s. The ion exchange capacity reaches 1.298 mmol g–1 and retains 93.5% of its initial value even after 1000 uptake/release cycles. Separation factors of 6.3, 5.6, and 6.2 for Ni2+/Ca2+, Ni2+/K+, and Ni2+/Na+, respectively, are obtained. These characteristics are attributed to the high identification capability of the ion-imprinted composite film for the target ions and the dual driving forces resulting from both PPy and FCN during the redox process. It is expected that the present method can be used for simple preparation of other ion-imprinted composite films for the separation and recovery of target heavy metal ions as well.Keywords: ferricyanide; heavy metal ions; ion-imprinted; polypyrrole; selective removal;

•NiHCF film was uniformly deposited on the surface of single carbon fiber by UPED method.•High pulse potential resulted in excellent ESIX performances of NiHCF film.•The optimum fabrication condition was found.•Insoluble NiHCF film showed good regeneration ability and long-term cycle stability.•Fabric ESIX film could be prepared for separation of Cs ions from radioactive liquid wastes.Nickel hexacyanoferrate (NiHCF) film was successfully deposited on carbon fibers by unipolar pulse electrodeposition (UPED) method. The effects of pulse potential and cycle number during the film deposition on the composition, regeneration ability and cycle stability of the film were investigated.The morphology, composition and electrochemical behavior of the as-fabricated NiHCF film were varied with the deposition conditions, and two structural analogues, i.e., soluble and insoluble NiHCFs, could be appeared together or alone in the finally obtained films. Especially, it is found that higher pulse potential was necessary to obtain high-quality NiHCF film on the carbon fiber than on metal electrode. In this study, when the pulse potential during the unipolar deposition of NiHCF film was set at a condition of 0.8 V with 0.5 s on-time, 0.5 s off-time and 3000 cycles, a film with insoluble structural analogue was obtained and it showed large ion exchange capacity, good regeneration ability and long-term cycle stability.

•All cis-PANI nanotube films were obtained using a facile UPEP method.•The formation mechanism of all cis-PANI films was proposed.•All cis-PANI nanotube films exhibited an excellent cycling stability.•All cis-PANI films showed an improved electrochemical capacitance performance.•All cis-PANI films had high electrocatalytic activity to ascorbic acid.An all cis-polyaniline nanotube film was successfully prepared using a novel unipolar pulse electro-polymerization method and its formation mechanism was analyzed and discussed. Due to its unique chemical molecular conformation, many excellent performances such as low charge transfer resistance, good water wettability, high apparent diffusion coefficient, large redox site capacity and super-stability were identified. When it was applied for the supercapacitor electrode, a high specific capacitance of 1007.7 F g−1 with a dramatic retention life of 99% after 2000 charge/discharge cycles was obtained. The ascorbic acid sensor fabricated by this film showed a large linear range for the detection of ascorbic acid between 1.0 × 10−6 and 1 × 10−2 M with a high sensitivity of 182 mA M−1 cm−1.

•Superstable PPy thin film was fabricated using a facile UPEP method.•The growing PPy film was found to keep at an oxidized state during polymerization process.•Ordered structure with reduced chain defects of PPy film was obtained.•The PPy film exhibited an excellent cycling stability even in a neutral solution.Polypyrrole (PPy) film was fabricated on platinum substrate by a facile unipolar pulse electro-polymerization (UPEP) method. Mechanism for the formation of highly stable PPy film was proposed based on the chronoamperogram obtained during the polymerization process. Structure, surface morphology and hydrophilic property of the PPy film prepared using either UPEP method or potentiostatic method (PM) were characterized by Fourier transfer infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and contact angle goniometer, respectively. Electrochemical performances of PPy films prepared by UPEP and PM were compared using cyclic voltammetry (CV), galvanostatic charge/discharge tests and electrochemical impedance spectroscopy (EIS) in 1.0 M of KCl solution. It is found that the PPy film prepared by UPEP method under the conditions of ultra short on-time pulse (10 ms) and low temperature (10.0 °C) showed an ordered structure with reduced chain defects and exhibited high specific capacitance and excellent cycling stability in neutral solution. The capacitance of such a PPy film electrode retained 93.6% of its initial value even after 50,000 charge/discharge cycles. The specific capacitance of the UPEP PPy film reached 406.0 F g−1 at a scan rate of 5 mV s−1 when temperature, pulse potential, pulse time ratio (ton/toff) and pulse cycles were 10.0 °C, 0.7 V, 10 ms/100 ms and 12,000, respectively.Graphical abstract

A novel unipolar pulse electro-polymerization (UPEP) method was used to prepare nanorod polyaniline (PANI) films on platinum substrates from aqueous solution containing 0.2 mol L−1 of aniline and 0.5 mol L−1 of sulphuric acid. The unipolar pulse waveform consisted of an applied anodic potential during the on-period and an open-circuit potential (zero current) during the off-period. The effects of pulse deposition parameters on the electrochemical properties of PANI films were investigated by potential cycling in 0.5 mol L−1 of H2SO4 solution. The supercapacitive performances of as-prepared PANI films were also investigated in the 0.5 mol L−1 of H2SO4 solution via charge/discharge tests as well as electrochemical impedance spectroscopy (EIS). The surface morphology and conformation of PANI films were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. Experimental results indicated that nanorod PANI films with uniform distribution on Pt were formed by using this novel method, and the anodic pulse potential should be the primary factor to influence the morphology and the conformation of PANI film. The PANI films prepared by UPEP method displayed much higher ion exchange capacity, better stability and more excellent supercapacitive performances than those by other methods such as the common cyclic voltammetric method (CVM) and potentiostatic method (PM). It should be attributed to the highly porous nano-sized PANI with short-fiber or rod-like structure and the depressed hydrolysis of aniline. The highest specific capacitance value of 907.9 F g−1 was obtained when the pulse potential, aniline concentration, pulse frequency and duty cycle were 0.85 V, 0.2 mol L−1, 1.25 s−1 and 50%, respectively.Highlights► A novel UPEP method was reported to prepare the nanorod PANI thin films. ► The morphology and conformation of nanorod PANI can be controlled by UPEP. ► The synthesized PANI films have the ordered and short-nanofiber or nanorod structure.

Unipolar pulse electrodeposition was used to prepare nickel hexacyanoferrate (NiHCF) films on platinum substrates with controllable structure. The unipolar pulse waveforms consisted of an applied cathodic potential during the on-period and the open-circuit potential during the off-period. The effects of the pulse deposition parameters on the electrochemical properties of NiHCF films were investigated by potential cycling in K+-containing electrolytes. The morphology and composition of NiHCF films were characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy. The charge transfer and the stability of the film electrodes were also examined by cyclic voltammetry (CV). Experimental results show that the cathodic pulse potential is the primary factor influencing the composition of the NiHCF films. The structure of NiHCF films prepared with a pulse potential of 0.7 V SCE appears close to that of the “insoluble” form with a single reversible CV peak at lower voltage and a unit cell with a stoichiometry close to KNi4II[FeIII(CN)6]3. These films exhibit good stability and high dynamics for charge transport. The application of more negative cathodic potential pulses produces less dense and robust NiHCF films, with a structure closer to the “soluble” form and an approximate stoichiometry K8Ni4II[FeII(CN)6]4.

Unipolar pulse waveforms consist of an applied anode potential during the on-period and an open-circuit potential during the off-period. Unipolar pulse electrodeposition (UPED) was used to fabricate nickel hexacyanoferrate/chitosan/carbon nanotubes (NiHCF/CS/CNTs) nanocomposite films with controllable structure on the electrode surface of a hydrogen peroxide (H2O2) sensor. One-step electrodeposition of NiHCF/CS/CNTs film with insoluble-structure NiHCF nanoparticles was performed, and the whole procedure took only several minutes. The morphology and the composition of the NiHCF/CS/CNTs film were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS). With the introduction of CNTs, the NiHCF/CS/CNTs system formed showed synergy between CNTs and NiHCF with a significant improvement of redox activity of NiHCF due to the excellent electron-transfer ability of CNTs. Electrochemical experiments revealed that the modified electrode allowed low potential (−0.2 V) detection of H2O2 and showed high electrocatalytic activity towards the reduction of H2O2. The linear range for the detection of H2O2 was 0.04–5.6 mM with a high sensitivity of 654 mA M−1 cm−2 and a rapid response (less than 2 s). The detection limit for H2O2 was as low as 2.8 × 10−7 M (S/N = 3).

•Amorphous α-ZrP/PANI film was first synthesized in aqueous solution by CV method.•The obtained hybrid film had excellent cation exchange property.•Rapid ion exchange process was controlled by the potential-triggered mechanism.•α-ZrP could provide acid micro-environment for PANI’s electroactivity.•Exfoliated α-ZrP enhanced the adsorption capability towards Pb2+ ions.An electroactive hybrid film composed of amorphous α-zirconium phosphate and polyaniline (α-ZrP/PANI) is controllably synthesized on carbon nanotubes (CNTs) modified Au electrodes in aqueous solution by cyclic voltammetry method. Electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM) and X-ray power diffraction (XRD) analysis are applied for the evaluation of the synthesis process. It is found that the exfoliated amorphous α-ZrP nanosheets are well dispersed in PANI and the hydrolysis of α-ZrP is successfully suppressed by controlling the exfoliation temperature and adding appropriate supporting electrolyte. The insertion/release of heavy metals into/from the film is reversibly controlled by a potential-triggered mechanism. Herein, α-ZrP, a weak solid acid, can provide an acidic micro-environment for PANI to promote the electroactivity in neutral aqueous solutions. Especially, the hybrid film shows excellent potential-triggered adsorption of Pb2+ ion due to the selective complexation of Pb2+ ion with oxygen derived from POH of α-ZrP. Also, it shows long-term cycle stability and rapid potential-responsive adsorption/desorption rate. This kind of novel hybrid film is expected to be a promising potential-triggered ESIX material for separation and recovery of heavy metal ions from wastewater.Download full-size image

•Functionalization of MWCNTs by silanisation and Micheal-addition reactions in one-pot.•The high molecular weight of perfluoroalky acrylate yields high grafting content.•MWCNTs/PU composites with high surface hydrophobicity, low percolation threshold and high strain.A facile approach has been developed to prepare perfluoroalkylsilane functionalized multi-walled carbon nanotubes (MWCNTs) with high grafting content through one-pot two-step reactions. In this process, hydroxyl derivatized MWCNTs (hydroxylized MWCNTs) were covalently functionalized with 3-aminopropyl triethoxysilane by silanisation reaction, and subsequently reacted with hexafluorobutyl acrylate or dodecafluoroheptyl acrylate by Micheal-addition reaction. SEM, FT-IR and TGA characterizations demonstrated that the perfluoroalkylsilane were covalently attached onto the surface of MWCNTs and the higher molecular weight of perfluoroalky acrylate yielded higher grafting content. The perfluoroalkylsilane functionalized MWCNTs showed improved dispersibility and strong interfacial adhesion in/with polyurethane matrix. An increase in the grafting content led to a decrease the crystallinity and hydrogen bonding in the PU composites. As a result, the composites showed increased elongation and unimproved tensile strength, but reduced storage modulus and loss factor. Meanwhile, the higher grafting content offered their composite with higher hydrophobicity, lower percolation threshold and more enhanced electronic conductivity.

A series of new hydroxypyridine-based ionic liquids (ILs) are synthesized and applied in CO2 capture through chemical absorption, in which one IL, i.e., tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]), shows a viscosity as low as 193 cP with an absorption capacity as high as 1.20 mol CO2 per mol IL. Because the traditional anion–CO2 absorption mechanism cannot provide an explanation for the influences of cations and temperature on CO2 absorption capacity, herein, a novel cation-participating absorption mechanism based on the proton transfer is proposed to explain the high absorption capacity and the existence of a turning point of absorption capacity with the increase of temperature for the capture of CO2 using [P4444][n-Op] (n = 2, 3, 4) ILs. Also, the relationship between the viscosity of ILs and the linear interaction energy is proposed for the first time, which can guide how to design and synthesize ILs with low viscosity. Quantum chemistry calculations, which are based on the comprehensive analysis of dipole moment, cation–anion interaction energy and surface electrostatic potential, indicate that the different viscosities of hydroxypyridine-based ILs and the changes after CO2 absorption mainly resulted from the different distribution of negative charges in the anion.

A novel electroactive Li+ ion-imprinted hybrid film consisting of λ-MnO2/PPy/PSS core–shell nanorods is successfully fabricated on an electrode by using the unipolar pulse electrodeposition (UPED) technique. When the electrode is applied for selective electrochemical extraction of low concentrations of Li+ ions from aqueous solutions via an electrochemically switched ion exchange (ESIX) process, the Li+ ion adsorption capacity reaches 35.2 mg g−1 with an adsorption equilibrium time of less than 2 h. The excellent ion separation performance of this hybrid film should be attributed to its low ion transfer resistance due to its porous structure and the high electric driving force during the ESIX process. In particular, owing to the unique Li+ ion imprinted vacant sites in the crystal structure of spinel λ-MnO2 nanorods, the selectivity factor for Li+/Na+ reaches 46.0 with a molar ratio of 1:1. It is expected that this λ-MnO2/PPy/PSS hybrid film can be applied as a promising electroactive material for effective separation of Li+ ions from seawater.

To achieve low cost, high rate and attractive capacity of CO2 adsorption by using ionic liquids (IL), a new mesostructured ionogel, pyridine-containing anion functionalized IL tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]) encapsulated silica MCM-41 (noted as PM-w), is fabricated by loading the IL [P4444][2-Op] with multiple active sites into porous silica MCM-41 through a simple moisture-controlled impregnation–evaporation method. Allosteric effect driven gas sorption on the electronegative oxygen and nitrogen atoms of the nanoconfined IL [P4444][2-Op] makes it take no more than 2 min for the ionogel PM-5 to achieve the 90% of saturated adsorption capacity. The corresponding adsorption rate is 30 times faster than that of the bulk IL. The ionogel PM-5 with the low IL loading of 5.0% shows the highest CO2 adsorption capacity up to 1.21 mmol (g-ionogel)−1 (14.89 mmol (g-IL)−1) at 50 °C in a gas mixture with N2, which is 9.25 times higher than that of the pure IL. Its excellent cyclic stability of more than 96% of the initial CO2 uptake repeatedly displayed after performing 10 cycles of adsorption–desorption tests. The enhanced thermal stability up to 450 °C in N2 is observed for the low loading ionogels since the strong interfacial layering of the IL prefers to dot the silica nanopores as monomolecular islands. Reversely, the high loading IL may aggregate into nanosized clusters that recover the poor thermal stability of the bulk IL. Reasonable decreases in their surface area, pore volume and pore size are observed with the IL loading up to 45%. They still exhibit highly ordered hexagonal mesostructures. The features of low loading and cost, rapid adsorption, high capacity and excellent cyclic stability make the ionogel PM-5 a competitive candidate in CO2 capture from flue gas.