Ion Transport Phenomena Research Articles

Bidirectional Transport Phenomenon of Ions in Electric Fields Due to the Cluster Formation in Two-Dimensional Graphene Channels

In aqueous solution, cations and anions are known to be moving oppositely and unidirectionally in electric fields. In this work, we observe an abnormal bidirectional ion transport phenomenon in electric fields because of the formation of ion clusters in two-dimensional graphene channels. A series of molecular dynamic simulations reveal that the separated ions within two-dimensional graphene channels will rapidly assemble into individual clusters under the electric field, originating from the confinement-induced effective ionic interactions as well as the strongly compressed hydration shells of ions. Notably, owing to the competition between ionic interaction and electric field, the structure of ion clusters changes from a square-unit pattern to chain-like with the increase in electric field, and the cluster size displays a maximum behavior. As a result, the motion of cations and anions in these clusters will be strongly coupled to each other, leading to the bidirectional transport phenomenon. Furthermore, these ion clusters will disappear abruptly with the increase in graphene layer distance, and thus the ion transport becomes unidirectional as normal. Our findings shed light on the unusual ion dynamics in two-dimensional channels and provide a potential avenue for the design of novel nanofluidic devices.

Fabrication of Ionic Cellulose Nanofiber Composites by Electrospinning Cellulose Microfibril-Gel-Dispersions in Poly(vinyl Alcohol) Solution

ABSTRACT In this study, we propose a fabrication method to obtain composites of poly(vinyl alcohol) (PVA)/ionic cellulose nanofibers, in which a fiber structure is manipulated through a reconstruction of 2,2,6,6-tetramethyl-piperidinyl-1-oxyl radical (TEMPO)-oxidized cellulose nanofiber (TCNF) or the carboxymethyl cellulose nanofiber (CMCNF) heterogeneous microfibril gels using electrospinning method. The key concept is to assemble nanofibers from thin few-nanometer-scale width cellulose nanofibers (microfibrils) to thicker several-hundred-nanometer-scale width cellulose nanofibers by electrospinning insoluble microfibril-gel-dispersion in PVA solution. In the case of CMCNF, nanofibers with less-fused structures were successfully reconstructed via electrospinning. Energy-dispersive X-ray spectroscopy revealed that sodium ions exist in the fibers, where they function as counter ions of carboxylate groups of polyelectrolyte moiety of CMCNF. Thus, the obtained composites do contain both ionic cellulose nanofibers and PVA. The proposed fabrication route can be used to fabricate composites as nonwoven fabrics of polyelectrolyte nanofibers. These natural polymer based ionic fabrics will be widely useful to propose low-environmental-impact polymer actuators and active sensing elements involving the ion transport phenomena.

(Invited) Interfacial Engineering of Battery Materials Using Atomic Layer Deposition

In batteries, like all electrochemical systems, interfacial phenomena play a critical role in thermodynamic stability, charge transfer kinetics, and ionic transport phenomena. For example, in Li-ion batteries, the solid-electrolyte interphase (SEI) layer enables stabilization of liquid electrolytes against continual electrolyte decomposition. In solid-state batteries, the dynamic morphological evolution of the interface results in unique electro-chemo-mechanical properties, which dictate performance, degradation, and ultimate failure.As a result of these coupled phenomena, there is a continued need to improve both our fundamental understanding of interfacial dynamics, as well as new strategies to engineer rationally-controlled interfaces. Among the various interfacial engineering methodologies, atomic layer deposition (ALD) has risen in interest in recent years, owing to its unparalleled ability to impart atomically-precise control of surface composition and structure, while maintaining conformal coating of ultra-high aspect ratio structures.In this talk, I will describe recent progress in applying ALD for battery applications. In the field of Li-ion batteries, I will show how deposition of a single-ion conducting solid electrolyte on the surface of graphite anodes can eliminate electrolyte decomposition and SEI formation, resulting in a four-fold decrease in interfacial resistance [1]. This results in lower cell polarization during fast charging, eliminating deleterious Li plating on the anode. In the field of Li metal batteries, I will also show how ALD coatings can influence nucleation and growth, resulting in improved Coulombic efficiency [2]. Finally, I will describe efforts towards incorporation of ALD films into solid-state batteries, where mechanical properties play a critical role [3-4].[1] E. Kazyak, K.-H. Chen, Y. Chen, T. H. Cho, N. P. Dasgupta, Adv. Energy Mater. 12, 2102618 (2022).[2] K.-H. Chen, A. J. Sanchez, E. Kazyak, A. L. Davis, N. P. Dasgupta, Adv. Energy Mater. 9, 1802534 (2019).[3] A. L. Davis, R. Garcia-Mendez, K. N. Wood, E. Kazyak, K.-H. Chen, G. Teeter, J. Sakamoto, N. P. Dasgupta, J. Mater. Chem. A 8, 6291 (2020)[4] E. Kazyak, M. Shin, W. S. LePage, T. H. Cho, N. P. Dasgupta, Chem. Commun. 56, 15537 (2020).

Characterization of the Surface Chemistry of Corroded and Non-Corroded Sites on Aluminum Alloys 2024-T3 and 7075-T6 Exposed at a Coastal Location

The last few decades have seen an improvement in the characterization of bare metal surfaces undergoing atmospheric corrosion, leading to a better understanding and consideration of the environmental parameters involved. However, in the quest for more reliable accelerated laboratory corrosion test methods, knowledge of the corrosion processes and the role that the environmental parameters play in those processes is critical in replicating the field exposure environment. The corrosion process occurs within a multiphase system that is rather complex involving chemical reactions and equilibria, ionic transport phenomena, and gaseous, aqueous and solid phases.1 Various corrosion products, specific to the metallic substrates in the system, and the corrosive species present (anions, cations, acidic and basic salts, particulates, etc.) which interact with each other all vary in amounts and residence time. It is well documented that corrosion behaviors of metal substrates in accelerated laboratory testsdo not correlate with the observed behaviors in an outdoor exposure environment. 2-6 Atmospheric constituents found on metal surfaces are a function of the atmosphere itself, with sulfates, nitrates, nitrites, chlorides, carbonates, hydrogen ions, ammonium, metal ions, particulates and organic compounds commonly found in electrolyte chemistries or corrosion layers. Each of these have an effect on the corrosion processes on exposed surfaces.7 These result either directly from the deposition processes or from aqueous phase reactions of the deposited atmospheric constituents. Sulfates, chlorides and cations such as sodium, magnesium, calcium, potassium and bromine can originate either directly from the wet deposition process, from particle deposition or from aerosol reactions of the gaseous air pollutants in the aqueous phase of the adsorbed electrolyte.1 In the present work, a matrix of epoxy-mounted AA2024-T3 and AA7075-T6 alloy samples were exposed to outdoor ambient environmental conditions at the Naval Research Laboratory-Key West (NRL-KW) facility for 18 months. Samples were retrieved for analysis at 3 month intervals. The field exposed samples were subjected to SEM/EDS for image and elemental analysis using a Zeiss Environmental Model EVO-50XVP scanning electron microscope integrated with an Energy Dispersive Analysis X-Ray (EDAX) Genesis 2000 EDS system. Images of the metal surfaces and compositional elemental data for the control (non-exposed) alloy samples were compared to the field exposed metal alloy samples in both the “as received” condition and after cleaning by sonication in deionized (DI) water. Pitted and non-pitted sites on each sample were analyzed for compositional elements of the alloy as well as non-compositional (i.e. environmentally-derived) elements. Any elements remaining on the surfaces after cleaning were considered to be well adhered, non-water-soluble corrosion products. The resulting concentrations of various environmental elements and their presence within or outside of pit sites were calculated as a percentage of their composition in natural seawater at NRL-KW and entered into a database. It was found that the elements chlorine, sulfur, potassium and calcium were present at higher concentrations on the metal surfaces than in natural seawater at NRL-KW; it was also found that sulfur concentrations were higher in the pits of the AA7075-T6 metal substrates than the surrounding non-pitted surfaces (Figure 1). Data analytics was performed to determine what environmental factors, if any, could be correlated with the observed presence of elements derived from atmospheric-seawater interaction and deposited onto the metal substrates. This work is currently supporting the development of an accelerated corrosion test protocol on identical bare metal alloy specimens using a modified laboratory atmospheric exposure chamber.References Cited Oesch, M. Faller, “Environmental Effects on Materials: The Effect of the Air Pollutants SO2, NO2, NO and O3 on the Corrosion of Copper, Zinc and Aluminum. A Short Literature Survey and Results of Laboratory Exposures,” Corrosion Science 39:9 (1997): p. 1505-1530. 2. Y. Wan, E. Macha, R. Kelly, “Modification of ASTM B117 Salt Spray Corrosion Test and Its Correlation to Field Measuremnets of Silver Corrosion,” Corrosion 68:3 (2012): p. 036001-1 to 036001-10. 3. Z. Feng, G. Frankel, W. Abbott, C. Matzdorf, “Galvanic Attack of Coated Al Alloy Panels in Laboratory and Field Exposure,” Corrosion 72:3 (2016): p. 342-355. 4. A. King, B. Kannan, J. Scully, “Environmental Degradation of a Mg-Rich Primer in Selected Field and Laboratory Environments: Part 1-Without a Topcoat,” Corrosion 70:5 (2014): p. 512-535. 5. D. Liang, H.C. Allen, G.S. Frankel, Z.Y. Chen, R.G. Kelly, Y. Wu, B.E. Wyslouzil, “Effects of Sodium Chloride Particles, Ozone, UV and Relative Humidity on Atmospheric Corrosion of Silver,” J. Electrochem. Soc. 157:4 (2010): p. C146-C156. Figure 1

(Invited) A Formalism Relating the Relative Humidity to the Proton Conductivity Mechanism of Membranes

The relationship between relative humidity of gas phase and proton conductivity in proton exchange membranes has been subject of extensive investigations [1],[2]. Herein, a theoretical framework is presented which describes proton transport in relation to stepwise equilibria that reflect the water uptake. In the proposed model, at first, the hydration process is treated as a stepwise equilibrium process, in agreement with experimental observations. Several hierarchical levels of structure evolve with increasing hydration. These levels are easily confirmed by the analysis of the electric response of perfluorinated based membranes by complex dielectric and conductivity spectra. Thus, a wide range of literature data on hydration of Nafion as a function of activity and temperature has been analyzed by means of the proposed model to extract chemical parameters diagnostic of the type of interactions characterizing the hydrophilic domains of membranes.These parameters, which are crucial in order to modulate the ion transport phenomena in ionomers, are then introduced into the model to describe the functional dependence of conductivity on water activity in gas phase. The treatment of proton conductivity is built on the approaches commonly adopted to describe transport in solids [3]. Key proton migration phenomena appropriate to the levels of the structural hierarchy are considered. The conductivity model is used to describe a set of conductivity vs. water uptake data as a function of temperature, with data taken to exceptionally low water contents. The formalism is then used to analyze a set of data for a perfluorosulfonic acid (PFSA) membrane as a function of hydration, temperature and polymer equivalent weight. The main advantage of the proposed framework is the possibility of a straightforward application to multiple membrane types based on the energetics of water uptake. Actually, the focus on chemical interactions allows to better correlate the effects of the morphology and relaxation events of the matrix to the proton migration phenomena of the membrane. Acknowledgements This work has received funding from: (a) the European Union’s Horizon 2020 research and innovation program under grant agreement 881603; (b) the project ‘Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells’ funded by EIT Raw Materials.

Bioinspired Dual-Driven Binary Heterogeneous Nanofluidic Ionic Diodes.

Recently, bioinspired 2D material-based nanofluidic systems with unique properties and advantages have been receiving considerable research interest and getting rapid development. However, it remains a huge challenge to integrate adaptive responsiveness to external stimuli and asymmetric ion transport characteristics into the 2D nanofluidic systems. Herein, we report a dual-driven switchable asymmetric ionic transport phenomenon through a graphene oxide-based heterogeneous 2D nanofluidic membrane. Taking advantage of the formation of a charge heterojunction induced by the variation of pH or UV irradiation, a maximum ionic current rectification (ICR) ratio of ca. 56 for pH or 140 for light was achieved. Such smart nanofluidic devices with pH and light dual-responsiveness and asymmetric ion transport behaviors provide a universal strategy for potential applications in chemical sensing, water treatment, and energy conversion and establish a promising platform for exploring advanced quantum ionics biodevices with ultrafast signal transmission, nanochannel-structured bioreactors with high efficiency, etc.

Probing Nanoconfined Ion Transport in Electrified 2D Laminate Membranes with Electrochemical Impedance Spectroscopy.

The recent emergence of electrically conductive nanoporous membranes based on graphene and other 2D materials opens up new opportunities to revisit some longstanding nanoconfined ion transport problems under electrification. This work probes the ionic resistance in electrified multilayered graphene membranes with electrochemical impedance spectroscopy. This study demonstrates that the combination of additive-free feature and tunable slit pore sizes in the sub-10nm range in graphene-based membranes has made it possible to deconvolute the different ionic processes from the impedance obtained and examine the exclusive influence of pore size on the ionic resistance in a quantitative manner. The trends revealed for the ionic resistance at the pore entrance and inside the pores under severe nanoconfinement (<2nm) are found to be generally consistent with the microscale theoretical simulations previously reported. It also allows a quantitative analysis of the relative effects of the external polarization potential and ion identity under nanoconfinement. The results suggest that the classic electrochemical impedance spectroscopy technique, when applied to appropriate nanoporous electrode materials, can provide rich information about nanoconfined ion transport phenomena under electrification for fundamental understanding and application development.

Ion slippage through Li+-centered G-quadruplex.

Single-ion conductors have garnered attention in energy storage systems as a promising alternative to currently widespread electrolytes that allow migration of cations and anions. However, ion transport phenomena of most single-ion conductors are affected by strong ion (e.g., Li+)–ion (immobilized anionic domains) interactions and tortuous paths, which pose an obstacle to achieving performance breakthroughs. Here, we present a Li+-centered G-quadruplex (LiGQ) as a class of single-ion conductor based on directional Li+ slippage at the microscopic level. A guanine derivative with liquid crystalline moieties is self-assembled to form a hexagonal ordered columnar structure in the LiGQ, thereby yielding one-dimensional central channels that provide weak ion-dipole interaction and straightforward ionic pathways. The LiGQ exhibits weak Li+ binding energy and low activation energy for ion conduction, verifying its viability as a new electrolyte design.

Effect of succinonitrile on ion transport in PEO-based lithium-ion battery electrolytes

We report the ion transport mechanisms in succinonitrile (SN) loaded solid polymer electrolytes containing polyethylene oxide (PEO) and dissolved lithium bis(trifluoromethane)sulphonamide (LiTFSI) salt using molecular dynamics simulations. We investigated the effect of temperature and loading of SN on ion transport and relaxation phenomenon in PEO-LiTFSI electrolytes. It is observed that SN increases the ionic diffusivities in PEO-based solid polymer electrolytes and makes them suitable for battery applications. Interestingly, the diffusion coefficient of TFSI ions is an order of magnitude higher than the diffusion coefficient of lithium ions across the range of temperatures and loadings investigated. By analyzing different relaxation timescales and examining the underlying transport mechanisms in SN-loaded systems, we find that the diffusivity of TFSI ions correlates excellently with the Li-TFSI ion-pair relaxation timescales. In contrast, our simulations predict distinct transport mechanisms for Li-ions in SN-loaded PEO-LiTFSI electrolytes. Explicitly, the diffusivity of lithium ions cannot be uniquely determined by the ion-pair relaxation timescales but additionally depends on the polymer segmental dynamics. On the other hand, the SN loading induced diffusion coefficient at a given temperature does not correlate with either the ion-pair relaxation timescales or the polymer segmental relaxation timescales.

Ionic liquid multistate resistive switching characteristics in two terminal soft and flexible discrete channels for neuromorphic computing

By exploiting ion transport phenomena in a soft and flexible discrete channel, liquid material conductance can be controlled by using an electrical input signal, which results in analog neuromorphic behavior. This paper proposes an ionic liquid (IL) multistate resistive switching device capable of mimicking synapse analog behavior by using IL BMIM FeCL4 and H2O into the two ends of a discrete polydimethylsiloxane (PDMS) channel. The spike rate-dependent plasticity (SRDP) and spike-timing-dependent plasticity (STDP) behavior are highly stable by modulating the input signal. Furthermore, the discrete channel device presents highly durable performance under mechanical bending and stretching. Using the obtained parameters from the proposed ionic liquid-based synaptic device, convolutional neural network simulation runs to an image recognition task, reaching an accuracy of 84%. The bending test of a device opens a new gateway for the future of soft and flexible brain-inspired neuromorphic computing systems for various shaped artificial intelligence applications.

Ion Transport in pH-Regulated Double-Barreled Nanopores.

Single-molecule detection and characterization with nanopores is a powerful technique that does not require labeling. Multinanopore systems, especially double nanopores, have attracted wide attention and have been applied in many fields. However, theoretical studies of electrokinetic ion transport in nanopores mainly focus on single nanopores. In this paper, for the first time, a theoretical study of pH-regulated double-barreled nanopores is conducted using three-dimensional Poisson-Nernst-Planck equations and Navier-Stokes equations. Four ionic species and the surface chemistry on the walls of the nanopores are included. The results demonstrate that the properties of the bulk salt solution significantly affect nanopore conductivity and ion transport phenomena in nanopores. There are two ion-enriched zones and two ion-depleted zones in double-barreled nanopores. Due to the symmetry of the double-barreled nanopore structure and surface charge density, there is no ionic rectification effect in double-barreled nanopores. The ion selectivity is similar to that of conventional single pH-regulated nanopores.

A study on Ti-doped Fe3O4 anode for Li ion battery using machine learning, electrochemical and distribution function of relaxation times (DFRTs) analyses

Among many transition-metal oxides, Fe3O4 anode based lithium ion batteries (LIBs) have been well-investigated because of their high energy and high capacity. Iron is known for elemental abundance and is relatively environmentally friendly as well contains with low toxicity. However, LIBs based on Fe3O4 suffer from particle aggregation during charge–discharge processes that affects the cycling performance. This study conjectures that iron agglomeration and material performance could be affected by dopant choice, and improvements are sought with Fe3O4 nanoparticles doped with 0.2% Ti. The electrochemical measurements show a stable specific capacity of 450 mAh g−1 at 0.1 C rate for at least 100 cycles in Ti doped Fe3O4. The stability in discharge capacity for Ti doped Fe3O4 is achieved, arising from good electronic conductivity and stability in microstructure and crystal structure, which has been further confirmed by density functional theory (DFT) calculation. Detailed distribution function of relaxation times (DFRTs) analyses based on the impedance spectra reveal two different types of Li ion transport phenomena, which are closely related with the electron density difference near the two Fe-sites. Detailed analyses on EIS measurements using DFRTs for Ti doped Fe3O4 indicate that improvement in interfacial charge transfer processes between electrode and Li metal along with an intermediate lithiated phase helps to enhance the electrochemical performance.

Ionic heat dissipation in solid-state pores.

Energy dissipation in solid-state nanopores is an important issue for their use as a sensor for detecting and analyzing individual objects in electrolyte solution by ionic current measurements. Here, we report on evaluations of heating via diffusive ion transport in the nanoscale conduits using thermocouple-embedded SiNx pores. We found a linear rise in the nanopore temperature with the input electrical power suggestive of steady-state ionic heat dissipation in the confined nanospace. Meanwhile, the heating efficiency was elucidated to become higher in a smaller pore due to a rapid decrease in the through-water thermal conduction for cooling the fluidic channel. The scaling law suggested nonnegligible influence of the heating to raise the temperature of single-nanometer two-dimensional nanopores by a few kelvins under the standard cross-membrane voltage and ionic strength conditions. The present findings may be useful in advancing our understanding of ion and mass transport phenomena in nanopores.

Controlling transmembrane ion transport via photo-regulated carrier mobility.

Stimuli-responsive transmembrane ion carriers allow for targeted and controllable transport activity, with potential applications as therapeutics for channelopathies and cancer, and in fundamental studies into ion transport phenomena. These applications require OFF–ON activation from a fully inactive state which does not exhibit background activity, but this remains challenging to achieve with synthetic transport systems. Here we introduce a novel mechanism for photo-gating mobile ion carriers, which involves modulating the mobility of the carriers within the lipid bilayer membrane. By appending a membrane-targeting anchor to the carrier using a photo-cleavable linker, the carrier's ion transport activity is fully switched off by suppressing its ability to shuttle between the two aqueous-membrane interfaces of the bilayer. The system can be reactivated rapidly in situ within the membrane by photo-triggered cleavage of the anchor to release the mobile ion carrier. This approach does not involve direct functionalization of the ion binding site of the carrier, and so does not require the de novo design of novel ion binding motifs to implement the photo-caging of activity. This work demonstrates that controlling the mobility of artificial transport systems enables precise control over activity, opening up new avenues for spatio-temporally targeted ionophores.

Putting together the puzzle of ion transfer in single-digit carbon nanotubes: mean-field meets ab initio.

Nature employs channel proteins to selectively pass water across cell membranes, which inspires the search for bio-mimetic analogues. Carbon nanotube porins (CNTPs) are intriguing mimics of water channels, yet ion transport in CNTPs still poses questions. As an alternative to continuum models, here we present a molecular mean-field model that transparently describes ion coupling, yet unlike continuum models, computes ab initio all required thermodynamic quantities for the KCl salt and H+ and OH- ions present in water. Starting from water transfer, the model considers the transfer of free ions, along with ion-pair formation as a proxy of non-mean-field ion-ion interactions. High affinity to hydroxide, suggested by experiments, making it a dominant charge carrier in CNTPs, is revealed as an exceptionally favorable transfer of KOH pairs. Nevertheless, free ions, coexisting with less mobile ion-pairs, apparently control ion transport. The model well explains the observed effects of salt concentration and pH on conductivity, transport numbers, anion permeation and its activation energies, and current rectification. The proposed approach is extendable to other sub-nanochannels and helps design novel osmotic materials and devices.

Numerical Analysis of Identification of Ion Species Using Nanochannels

Recently, ionic current responses in mico- and nanofluidic channels have attracted significant attention from both fundamental and application perspectives in various research fields. For single particle analysis, ionic current responses are often caused by interactions between electrolyte ions and target particles as well as the volume exclusion effect due to the transport of target particles. Therefore, the behavior of ions in narrow confined spaces is required to measure more precisely to obtain detailed information of particles. In this study, we propose a novel method to identify ion species in electrolyte solutions, using the ion selectivity of nanochannels. Applying an external potential on an electrolyte solution for a probe, which is separated from a sample solution by a nanochannel, ion concentrations are separately determined. As a result, it is found that electroosmotic flows have an important role to distinguish ion species, breaking a symmetry of ion transport phenomena that are dominated by diffusion and electrophoretic transport.

Bidirectional Light-Driven Ion Transport through Porphyrin Metal–Organic Framework-Based van der Waals Heterostructures via pH-Induced Band Alignment Inversion

Bidirectional Light-Driven Ion Transport through Porphyrin Metal–Organic Framework-Based van der Waals Heterostructures via pH-Induced Band Alignment Inversion

Crystal Channel Engineering for Rapid Ion Transport: From Nature to Batteries.

Ion transport behaviours through cell membranes are commonly identified in biological systems, which are crucial for sustaining life for organisms. Similarly, ion transport is significant for electrochemical ion storage in rechargeable batteries, which has attracted much attention in recent years. Rapid ion transport can be well achieved by crystal channels engineering, such as creating pores or tailoring interlayer spacing down to the nanometre or even sub-nanometre scale. Furthermore, some functional channels, such as ion selective channels and stimulus-responsive channels, are developed for smart ion storage applications. In this review, the typical ion transport phenomena in the biological systems, including ion channels and pumps, are first introduced, and then ion transport mechanisms in solid and liquid crystals are comprehensively reviewed, particularly for the widely studied porous inorganic/organic hybrid crystals and ultrathin inorganic materials. Subsequently, recent progress on the ion transport properties in electrodes and electrolytes is reviewed for rechargeable batteries. Finally, current challenges in the ion transport behaviours in rechargeable batteries are analysed and some potential research approaches, such as bioinspired ultrafast ion transport structures and membranes, are proposed for future studies. It is expected that this review can give a comprehensive understanding on the ion transport mechanisms within crystals and provide some novel design concepts on promoting electrochemical ion storage capability in rechargeable batteries.

Enhancement of the electron transfer and ion transport phenomena in microbial fuel cells containing humic acid-modified bioanodes

Although microbial fuel cells (MFCs) are an attractive alternative to environmental remediation and power generation, there are still significant limitations related to power density and coulombic efficiency. Previous works have shown that the addition of humic acids (HA, a type of organic matter contained in soils and composting-by-products), improves the fuel to electricity conversion at the porous bioanodes (ba)|anolyte junction. In this work, MFCs having HA-modified bioanodes (MFC/baHA) were prepared and electrochemically analyzed utilizing discharge curves (cell potential vs current density plots) and electrochemical impedance spectroscopy (EIS). This investigation was motivated by looking for a deeper understanding of the functional effects of HA molecules on the operation of baHA-containing Microbial Fuel Cells (MFC/baHA). Our results revealed that the modification of bioanodes with HA molecules decreases the activation energy of the acetate ion oxidation, increasing by a factor of three the consumption rate of this fuel at the baHA|anolyte interface, and enhancing the diffusive transport of these ions through the pores of the baHA permeated by the anolyte.

Ionic Transport Triggered by Asymmetric Illumination on 2D Nano-Membrane.

Ionic transport and ion sieving are important in the field of separation science and engineering. Based on the rapid development of nanomaterials and nano-devices, more and more phenomena occur on the nanoscale devices in the field of thermology, optics, mechanics, etc. Recently, we experimentally observed a novel ion transport phenomenon in nanostructured graphene oxide membrane (GOM) under asymmetric illumination. We first build a light-induced carriers’ diffusion model based on our previous experimental results. This model can reveal the light-induced ion transport mechanism and predict the carriers’ diffusion behavior under different operational situations and material characters. The voltage difference increases with the rise of illuminate asymmetry, photoresponsivity, recombination coefficient, and carriers’ diffusion coefficient ratio. Finally, we discuss the ion transport behavior with different surface charge densities using MD simulation. Moderate surface charge decreases the ion transport with the same type of charge due to the electrostatic repulsion; however, excess surface charge blocks both cation and anion because a thicker electrical double layer decreases effective channel height. Research here provides referenced operational and material conditions to obtain a greater voltage difference between the membrane sides. Also, the mechanism of ion transport and ion sieving can guide us to modify membrane material according to different aims.