Ion Transfer Behavior Research Articles

Straightforward electroanalytical sensing of nitrate in cyanobacteria growth media at electrified liquid-liquid interface

Nitrate is one among the necessary substance in the biosphere as its presence is pivotal to ensuring healthy vegetation and human health while its excess causes serious adversities. In this work, we utilized the electrified liquid-liquid interface (eLLI) and voltammetry to develop an alternative approach that enables onsite periodic monitoring of nitrate ions in cyanobacteria growth medium. The signal attributed to nitrate detection was directly related to its interfacial ion transfer behavior and not the redox properties. The ion transfer voltammograms of nitrate at eLLI delivered useful analytical parameters of linear detection range from 20 to 500 μM paired with detection and quantification limits of 1.5 and 14.6 μM, respectively. Further, the influence of chloride ions, and other anionic species present in the algae grow media were studied towards the determination of nitrates. We also optimized an in-situ chemical precipitation strategy to eliminate the influence of chloride ions that significantly improved the accuracy of the eLLI-based nitrate sensor. eLLI-based nitrate sensor delivered a remarkable analytical performance to determine nitrate levels in Z8 medium composed of nitrate and other nutrients (medium serving as the optimal environment for algae growth). eLLI based nitrate sensor was successful towards periodic monitoring of nitrate levels in Microcystis aeruginosa cyanobacteria samples cultured in Z8 medium.

Tunnel-Oriented VO2 (B) Cathode for High-Rate Aqueous Zinc-Ion Batteries.

Tunnel-type vanadium oxides are promising cathodes for aqueous zinc ion batteries. However, unlike layer-type cathodes with adjustable layer distances, enhancing ion-transport kinetics in tunnels characterized by fixed sizes poses a considerable challenge. This study highlights that the macroscopic arrangement of the electrode crucially determines tunnel orientation, thereby influencing ion transport. By changing the material morphology, the tunnel orientation can be optimized to facilitate rapid ion diffusion. In a proof-of-concept demonstration, it is revealed that (00l) facets-dominated VO2 (B) nanobelts with dispersive morphology (VO2-D) tend to adopt a stacking pattern with directional ion transport along the c-axis on the electrode and guarantee fast ion diffusion. Compared with the aggregated sample (VO2-A) that tends to random arrangement on the electrode with isotropic and slow ion transfer behavior, the electrode featuring dispersive (00l) facets-dominated VO2 (B) nanobelts displays directional and fast ion diffusion behavior, thus exhibits an ultrahigh-rate performance (420.8 and 344.8 mAh g-1 at 0.1 and 10 A g-1, respectively) and long cycling stability (84.3% capacity retention under 5000 cycles at 10 A g-1). The results suggest that simultaneous manipulation of exposed crystal facet and morphology-related electrode arrangement should be promising for boosting the ion-transport kinetics in tunnel-type vanadium oxide cathodes.

Electrokinetic energy conversion in nanochannels with surface charge-dependent slip

Electrokinetic energy conversion in nanochannels has attracted increasing attention in recent years. However, few scholars have studied the impact of the intrinsic distinction between surface charge-dependent and independent slip on power generation performance. In this work, we consider three kinds of boundary conditions, including no slip, independent slip and surface charge-dependent slip, to investigate the ion concentration distribution, velocity and energy conversion performance in nanochannels combined with the electric double layer theory. The results show that the boundary slip can improve the output performance significantly. Besides, due to the restriction of surface charge on boundary slip, the power generation performance under independent slip and dependent slip exhibits a significant deviation. Thus, the independent slip model is not suitable for predicting ion transport and fluidic flow in practical applications. Moreover, the ion concentration and channel height also play an optimizing role in the performance of electrokinetic energy conversion. We find the boundary slip is a benefit to promote the ion flux due to the velocity mechanism but has little effect on ion concentration distribution. The findings of this study can help for better understanding the ion transfer behavior in nanochannels, which provides useful information for the design and optimization of nanochannel power generation.

Importance of nanochannels shape on blue energy generation in soft nanochannels

Energy production is one of today's most pressing issues. Finding alternative energy sources has become one of the hottest research areas for scholars due to the limited use of fossil resources. Using water sources of different concentrations is one of the newest methods of energy production. Due to the energy of mixing fluids, two fluids of different concentrations on both sides of a nanochannel membrane can produce energy. Given the costs and restrictions of studying complex systems experimentally, simulation is required to investigate their behavior and determine the best states. As a result, using an energy production strategy, this work explores the effect of nanochannel shape on the ion transfer behavior. Asymmetric (bullet, trumpet, cigarette, hourglass, and hill) and symmetric (cylindrical) geometries were utilized. The effects of different geometries, soft layer density, and concentration ratio on energy production considering the effect of ion partitioning in soft surfaces was investigated. A finite element numerical computation approach was employed to solve the Poisson-Nernst-Planck and Navier-Stokes equations at steady-state. The best geometry at various concentration ratios to create the most performance were: cylindrical and cigarette for osmotic current, hourglass and trumpet for transmission number, hourglass and trumpet for diffusion potential, cylindrical for electrical conductivity, cylindrical and trumpet for power capacity, and hourglass and trumpet for energy conversion efficiency, respectively. In the case of considering the ion partitioning at a concentration ratio of CH/CL=1000for trumpet geometry, raising the soft layer's charge density from NPEL/NA=25to100mol/m3 boosted the maximum produced power by about 25 times, from 0.215pW to 5.35pW.

Influence of location junction on ion transfer behavior in conical nanopores with bipolar polyelectrolyte brushes

A bipolar ion diode consists of two positively and negatively charged surfaces that show the distribution of specific ions under different applied voltages. One of the most important electrokinetic phenomena occurring in bipolar nanopores is ionic current rectification (ICR). ICR in nanopores occur when, by applying a voltage to both ends of a nanochannel, the system exhibits non-linear current-voltage behavior or diode-like behavior, in other words, ionic current occurs in a specific direction. In modeling bipolar soft nanochannels, it is usually assumed that the properties of the soft layer and the electrolyte are the same, which is not true for soft layers with high charge densities. In the present work, the effect of sharp and wide aperture radius of nanochannels on ionic current rectification in bipolar nanochannels by coating polyelectrolytic layer with conical geometry in different values of soft layer lengths was studied. For this purpose, by adopting a numerical calculation approach Finite element, Poisson-Nernst-Planck and Navier-Stokes equations were solved for steady-state by considering different permeability values, diffusion coefficient, and dynamic viscosity for polyelectrolyte and electrolyte In general, it can be concluded that the bipolar conical nanopore has a higher ICR than the cylinder geometry with the same average radius If the junction is at the tip of the nanopore. For example, when the mole concentration was equal to c0=50mM, the ICR for the bipolar conical nanopore with a soft layer with an optimal junction at the tip of the nanopore reached 45, while in the bipolar cylindrical nanopore at best (the optimal junction in the middle of the nanopore) reached 25.

Palladium-coated polyaniline nanofiber electrode as an efficient electrocatalyst for hydrogen evolution reaction

In this study, polyaniline (PANI) with abundant protonated regions was used for the first time as a palladium (Pd) support for enhanced performance in hydrogen evolution reaction (HER). For this purpose, the hierarchical Pd@PANI nanofiber electrode was easily synthesized by electrochemical polymerization of aniline on Au followed by potential-controlled electrochemical deposition of Pd nanoclusters on the PANI. The reported catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy. Linear sweep voltammetry analysis was performed to evaluate the HER performance. Ion transfer behavior was investigated using electrochemical impedance spectroscopy analysis. The electrochemical tests show that the Pd@PANI/Au electrode has a low overpotential of ∼60 mV at 10 mA cm−2 and a small Tafel slope of 35 mV dec−1 for HER in acidic media, with high catalytic activity and stability. These features will make the Pd@PANI/Au a promising candidate as a high-performance electrocatalyst for HER applications.

Electrical conductivity and ion transfer behavior of NiCo2O4 with different micro structures

The commercial graphite anode material in lithium-ion batteries has been limited by the low capacity and safety issue own to its low Li-intercalation potential. Spinel transition metal oxides have attracted tremendous attention because their high specific capacity and relatively high Li-intercalation potential. Herein, we investigated the influence of micro-structure on the ion transport properties of NiCo2O4 and their electronic conductivity. The optimized material with nano-cluster constructed macro-sphere demonstrates weak crystal structure and improved electrical conductivity when surrounded with amorphous carbon. Electrochemical impedance spectroscopy (EIS) combined with CV results give more clear explanation of the improved charge transfer resistance and ion transfer properties, which suggests the readjustment of microstructure is an important route for improving electrical conductivity and ion transfer behavior of NiCo2O4 anode.

Ion Transfer Behavior of Protonated Phenazopyridine at the Liquid/Liquid Interface Modified by Functionalized Hybrid Mesoporous Silica Membrane†

Ion Transfer Behavior of Protonated Phenazopyridine at the Liquid/Liquid Interface Modified by Functionalized Hybrid Mesoporous Silica Membrane†

The porous membrane with tunable performance for vanadium flow battery: The effect of charge

Abstract Porous membranes with different charge on the surface and internal pore walls are prepared via the solvent-responsive layer-by-layer (SR-LBL) method. The effect of charge on the transport properties of different ions through the membranes is investigated in detail. The charge property of prepared membranes is tuned by assembling different charged polyelectrolytes (PEs) on the pore walls and the surface of the porous membranes. The results show that in a vanadium flow battery (VFB), the PE layers assembled on the surfaces (including pore walls) are capable to construct excellent ion transport channels to increase proton conductivity and to tune the ion selectivity via Donnan exclusion effect. Compared with the porous membrane with negative charges (7 bilayers), a VFB single cell assembled with a positively charged membrane (7.5 bilayers) yields a higher coulombic efficiency (98%). The water and ion transfer behavior exhibits a similar tendency. In the negative half-cell, the amount of V 3+ gradually increases as cycles proceed and the amount of V 2+ stays at a low and stable level. In the positive half-cell, the amount of VO 2+ decreases; while VO 2 + is accumulated. The imbalance of vanadium ions at both sides induces the discharge capacity fade.

Investigation of proton-driven amine functionalized tube array as ion responsive biomimetic nanochannels

A simple amine embellished tube array was assembled at the liquid–liquid interface to study ion transfer behavior.

Structurally modified aromatic sulfone polymer nanocomposites as polyelectrolyte membranes

A candid approach to analyze the prospects of organic–inorganic nanocomposites as polyelectrolytes has been presented in this communication. Structurally modified aromatic sulfone polymer, polysulfone, was successfully prepared through modification with trimethyl silyl chlorosulfonate, which was confirmed from Fourier transform infrared spectrographs. Different classes of nanofillers like layered silicates and inorganic oxides were reinforced in the modified macromolecular system using solvent casting technique. A comparative study was performed to evaluate the effectiveness of filled polyelectrolyte membranes in a direct methanol fuel cell operated at 60°C with 1.0 M methanol feed. Atomic force micrographs revealed the phase morphology, responsible for this behaviour. The variation in ion transfer behavior as a function of structural modification and filler composition was also conducted. Furthermore, supportive information for these characterizations were derived from morphological (x-ray diffractometry), thermal (thermogravimetric analysis), and liquid uptake studies.

A Facile Synthesis of a Palladium-Doped Polyaniline-Modified Carbon Nanotube Composites for Supercapacitors

Supercapacitors have evolved as the premier choice of the era for storing huge amounts of charge in the field of energy storage devices, but it is still necessary to enhance their performance to meet the increasing requirements of future systems. This could be achieved either through advancing the interfaces of the material at the nanoscale or by using novel material compositions. We report a high-performance material composition prepared by combining a transition metal (palladium)-doped conductive polymer with multiwalled carbon nanotubes (MWCNTs). MWCNTs/palladium-doped polyaniline (MWCNTs/Pd/PANI) composites and multiwalled carbon nanotube/polyaniline (MWCNTs/PANI) composites (for comparison) were prepared via in situ oxidative polymerization of aniline monomer. The reported composites were characterized by Fourier-transform infrared (FTIR), x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) studies. FESEM and TEM studies indicated the narrow size distribution of the π-conjugated polymer-protected palladium nanoparticles on the surface of the carbon nanotubes. All the electrochemical characterizations were executed using a three-electrode system in 1 M H2SO4 electrolyte. Cyclic voltammetry (CV) analysis was performed to observe the capacitive performance and redox behavior of the composites. The ion transfer behavior and cyclic stability of the composites were investigated by electrochemical impedance spectroscopy (EIS) analysis and cyclic charge–discharge (CCD) testing, respectively. The MWCNTs/Pd/PANI composite was found to exhibit an especially high specific capacitance value of 920 F/g at scan rate of 2 mV/s.

Influence of pore structures on the electrochemical performance of asphaltene-based ordered mesoporous carbons

Three ordered mesoporous carbons (OMCs) with different pore structures and pore arrangements were synthesized by template method using silicas as template and asphaltene as carbon source. The microstructures of the OMCs were characterized by X-ray diffraction and nitrogen adsorption techniques. The as-made OMCs had two-dimensional (2D) hexagonal symmetry, 3D body-centered cubic Im3¯m symmetry and 3D bicontinuous cubic Ia3¯d symmetry. All of the OMCs exhibit similar pore volume, pore size distribution and BET surface area. Their electrochemical performance as electrode materials for supercapacitors was investigated by cyclic voltammetry, galvanostactic charge–discharge, and electrochemical impedance spectroscopy techniques to assess the ion transfer behavior and charge storage capacity in different mesopore structures. The OMCs with different mesopore shapes and connectivity show different capacitances and ion transport behaviors. In terms of the ion transport kinetics, OMC with 2D hexagonal symmetry has the best ionic diffusion performance and lowest impedance for the long ordered pore channels. However, the OMC with 3D bicontinuous cubic Ia3¯d symmetry exhibits the best charge storage capacity because of the tortuosity of bicontinuous mesostructure.

Electrochromic response, structure optimization and ion transfer behavior in viologen adsorbed titanium oxide films

Nanostructured TiO 2 films have been fabricated using a simple wet chemistry route and the post-deposition annealing temperature has been optimized on the basis of crystal structure, particle and pore size, reflectance (diffuse) and band gap. The film annealed at 700 °C with a rutile structure, equipped with mesopores of 15 to 30 nm dimension, high diffuse reflectance ( R max = 91%) and an indirect band gap of 2.5 eV was found to be most suitable for the adsorption of bis-(2-phosphonoethyl)-4,4′-bipyridinium dichloride (viologen). The electroactive behavior of the viologen adsorbed TiO 2 film as a function of reduction level and in oxidized and neutral states has been followed by cyclic voltammetry and electrochemical impedance spectroscopy through equivalent circuits and compared with the response of blank TiO 2. It has been shown that interfacial charge transfer resistance governs ion intercalation during coloration with little contribution from the charge transfer and double layer capacitive components. The remarkable coloration efficiency (203 cm 2 C − 1 , λ = 720 nm) and good reversibility of the color-bleach process for viologen adsorbed TiO 2 films have been found to be closely linked to the microstructure of the oxide layer.

Mixed ion transfer in redox processes of poly(3,4-ethylenedioxythiophene)

A model considering the transfer of counter ions and solvent molecules has been presented to explain the complicated ion transfer in polymer films during electrochemical redox processes. The developed mixed ion transfer model is used to analyze the ion transfer behavior of poly(3,4-ethylenedioxythiophene) during doping and dedoping processes. The results indicate that both anions and cations are involved in n-doping as well as in p-doping processes. The behavior of different electrolyte ions is also studied. The developed model shows that solvent molecules are also transferred in conjunction with the ion transfer.