Activation Energy For Transport Research Articles

Temperature Dependent EIS Studies Separating Charge Transfer Impedance from Contact Impedance in Lithium-Ion Symmetric Cells

Measuring electrochemical impedance spectra of lithium-ion symmetric cells at low temperatures allows for unambiguous separation of charge transfer impedance contributions from other cell impedance features. Electrodes from dry Li[Ni0.5Mn0.3Co0.2]O2 (NMC 532)/artificial graphite (AG) pouch cells were used to make blocking electrode configuration symmetric cells and blocking electrode full coin cells. NMC532/AG cells with 1.2M LiPF6 in EC:DMC 3:7 (w:w) electrolyte also underwent the formation process before the electrodes were used to make non-blocking configuration symmetric and full coin cells. Through the use of temperature dependent measurements on blocking and non-blocking cells, the impedance contribution due to faradaic, charge transfer interactions can be distinguished from non-faradaic, high frequency impedance contributions. Fitting the EIS spectra allowed both the charge transfer resistances and the related capacitances to be determined for the solid electrolyte interphase layers on the negative and positive electrodes. The charge transfer resistances were strongly temperature dependent while the capacitances were not. The temperature dependence of the charge transfer resistance was used to determine the activation energies for lithium transport through the solid electrolyte interphase layers on the negative and positive electrodes. Surprisingly, the activation energies were approximately 0.6 eV for both positive and negative electrodes extracted from cells after formation.

Synthesis of Ionic Conductive Gels by Means of Menschutkin Reaction of Poly(epichlorohydrin) and Bisimidazole Compounds

Ionic conductive gels have been synthesized by means of Menschutkin reaction of poly(epichlorohydrin) (PECH) and 1,n-alkanediyl-bis-imidazolium (BIn, n = 4, 6, 8) in acetonitrile or 1,4-dioxane. The obtained gels showed soft and flexible features. The gels showed ionic conductivity derived from Cl− anions in PECH. The ionic conductivity of the gel in acetonitrile showed higher conductivity than that in 1,4-dioxane. The ionic conductivity increased with increasing of the molecular length of BIn. Temperature dependence of the gels was investigated to determine Vogel-Tammann-Fulcher (VTF) equation parameters. The results indicated that increasing of the crosslinking density accompanied by decrease of the molecular length of BIn should prevent the Cl− anions from diffusing in the gels due to the increase of activation energy of the ion transport.

Concentration effects on the thermally-activated transport of polarons in conducting polymers

The impact of the polaron concentration on the temperature-mediated charge transport in one-dimensional organic materials is studied. Within the scope of a tight-binding description, our findings reveal that high-temperature diffusivity tends to increase as polaron concentration increases. Moreover, the activation energy for the polaron transport also increases with polaron concentration. Importantly, the polaron diffusivity follows an Arrhenius-like behavior with low activation energy.

A spin glass state in Ba3TiRu2O9

The magnetic properties of Ba3TiRu2O9 , whose crystal structure is based on stacked triangular planar lattices of MO6 dimers and single MO6 octahedra, are reported. The system is magnetically disturbed by a substantial amount of Ti/Ru chemical disorder. The Weiss temperature and effective magnetic moment were found to be -29.5 K and 1.82 {\mu}B/f.u. respectively, and a bifurcation in the zero field cooled and field cooled magnetic susceptibility is observed below 4.7 K, suggesting that this is a compositionally-disordered spin-glass system. The material is a semiconductor with an activation energy for charge transport of approximately 0.14 eV.

Synthesis of Joint-Linker Type Ionic Gels Containing Imidazole Units in the Network

Joint-linker type gels have been synthesized by means of thiol-ene reaction of tri-functional thiol and bis-vinylimidazole compounds, or Menschutkin reaction of multi-functional bromomethyl benzene, and bis-imidazole compound in dimethylsulfoxide (DMSO). The gels showed ionic conductivity derived from anions in the linker molecules. The ionic conductivity of the gels decreased with increasing of the monomer concentration. Temperature dependence of the gels was investigated to determine Vogel-Tammann-Fulcher (VTF) equation parameters. The results indicated that increasing of the crosslinking density should prevent the anions from diffusing in the gels due to the increase of activation energy of the ion transport. The gel with bis-vinylimidazole [BF4] showed higher ionic conductivity than the corresponding gel with [Br] due to higher dissociation the ion carrier. Addition of a protonic solvent, methanol, to DMSO was effective to increase the ionic conductivity.

Ion-Transport Engineering of Alkaline-Earth Hydrides for Hydride Electrolyte Applications

The heavier alkaline-earth hydrides (AeH2; Ae = Ca, Sr, Ba) are promising materials for hydrogen energy applications, due to their excellent ionic conductivity and thermal stability. We use first-principles calculations to elucidate their defect chemistry and ion-transport mechanisms. On the basis of calculated formation energies, we find that hydrogen vacancies (VH) are present in large concentrations, and hence, transport is vacancy-mediated. The vacancy migration barrier depends strongly on the charge state of the vacancy, with VH+ yielding the lowest barriers. The activation energy for ionic transport, which is the sum of the migration barrier and formation energy, can be further reduced by lowering the formation energy of the vacancies. This goal can be achieved by doping with acceptors, such as alkali-metal impurities, which induces larger concentrations of VH+. We show that, with optimized conditions for doping, ionic conductivities can be improved by several orders of magnitude; for BaH2, the cond...

Current Enhancement and Bipolar Current Modulation of Top-Gate Transistors Based on Monolayer MoS2 on Three-Layer W xMo1- xS2.

We demonstrated the top-gate transistors composed of monolayer MoS2 grown on three-layer alloys Mo xW1- xS2 prepared by sequential sulfurization of predeposited transition metal films. The elemental mapping of the alloy indicates a uniform distribution of both cations Mo and W in the grown samples. Surprisingly, we find that the drain current of transistors could be enhanced by 2 orders of magnitude as the composition of Mo increases, whereas the gate-controlled current modulation turns bipolar and ultimately vanishes. These features might originate from the formation of in-gap defect states, with modest activation energy for transport and moderate hopping probability for current conduction, or a reduced electronic band gap of the conducting channel because of strain.

Enhanced proton transport properties of Nafion via functionalized halloysite nanotubes

The introduction of naturally occurring fibrillary structured halloysite clays (HNTs) into the Nafion matrix resulted in an enhanced proton conductivity and a reduced activation energy for proton transport. To assess the effect of the various states of the HNTs as a membrane additive, the σH+ of the composite membranes (Nafion/HNTs, Nafion/HNTs-NH2, Nafion/HNTs-SO3H) was measured at 30 °C and 80 °C and at different levels of relative humidity (%RH). An overall improvement of the σH+ of the Nafion was observed in the presence of the nanotubular additives (HNTs or HNTs-NH2) which can be attributed to the high specific surface area accommodating hydrophilic functional groups and therefore contributing to the water retention/management in the composite membrane. However, the Nafion/HNT-SO3H composites are distinguished in terms of enhanced performance in σH+ which persist in the whole range of % RH levels and noted that the σH+ values are almost 2 times higher than native Nafion in the low humidity region (30%–50%) and at 80 °C. In agreement with the σH+ enhancement, the activation energy is lower than that of native Nafion indicating that the proton transport is facilitated in the presence of -SO3H modified HNTs, probably due to an improved connectivity and arrangement of ionic conducting domains.

Pickering emulsion polymerization of poly(ionic liquid)s encapsulated nano-SiO2 composite particles with enhanced electro-responsive characteristic

Poly(ionic liquid)s (PILs) encapsulated nano-SiO2 composite particles were synthesized by a Pickering emulsion polymerization and used as stimuli-responsive electorheological (ER) particles, which showed enhanced electro-responsive effectiveness and temperature stability. Methacryloxypropyltrimethoxysilane modified nano-SiO2 particles with size of 15 nm were used as solid surfactant, which could not only help to form emulsion droplets of IL monomer but also immerse into droplets to form nanocomposite particles after polymerization. The morphology of the nanocomposite particles was characterized by scanning electron microscopy and transmission electron microscopy, while the chemical structure was analyzed by thermogravimetric analysis and Fourier transform infrared spectroscopy. Under electric field, ER property of the nanocomposite particles when dispersed in insulating oil was characterized by temperature-modulated rheology. Through comparing with pure PILs particles, we found that introducing nano-SiO2 into PILs particles could significantly suppress the excessive growth of leaking current density with increasing temperature and improve the electro-responsive ER effectiveness and temperature stability of ER property. Dielectric spectra analysis indicated that nano-SiO2 could act as cross-linking points to suppress the thermally promoted segment relaxation and improve the activation energy of the ion transport in PILs matrix, and this should be responsible for the enhanced electro-responsive ER effectiveness and temperature stability of PILs encapsulated nano-SiO2 composite particles.

Synthesis of an aliphatic hyper-branched polycarbonate and determination of its physical properties for solid polymer electrolyte use

An aliphatic hyper-branched polycarbonate (HBPC) was synthesized as a novel host material for solid polymer electrolytes (SPEs). The HBPC was synthesized through A2 + B3 polymerization to yield a branched polycarbonate structure. HBPC-based SPE films were prepared by drying mixed solutions of HBPC and 1–60 mol% LiClO4. The temperatures for 5% weight loss (Td5s) of the HBPC-based SPEs were in the range of 174.4–189.3 °C, higher than those in normal use. The HBPC-based SPE exhibited higher ionic conductivities (1.86 × 10−4 S∙cm−1 at 70 °C and 8.52 × 10−6 S∙cm−1 at 30 °C) than a poly(trimethylene carbonate) (LPC)-based SPE (4.79 × 10−6 S∙cm−1 at 70 °C and 8.32 × 10−8 S∙cm−1 at 30 °C) for 20 mol% lithium content. Activation energies of lithium ion transport for the HBPC- and LPC-based SPEs were estimated to be 11.47 and 15.88 kJ∙mol−1, respectively. Introduction of this branched structure in polycarbonates is effective for promoting lithium ion transport.

Electrical Conductivity of Cancrinite-Type Na8 − 2xCa x [Al6Si6O24][CO3] · 2H2O (x ≤ 0.03) Crystals

The electrical conductivity of crystals of artificial cancrinite Na8 − 2xCa x [Al6Si6O24][CO3] · 2H2O (x ≤ 0.03) has been studied in the temperature range of 498−604 K. These crystals were grown by hydrothermal synthesis on a seed in the Na2O–Al2O3–SiO2–H2O system (t = 380−420°С, P = 3 × 107−9 × 107 Pa). The ionic conductivity of a single-crystal sample (sp. gr. P63), measured along the crystallographic axis c, is low: σ = 8 × 10–7 S/cm at 300°С. The electric transport activation energy is Ea = 0.81 ± 0.05 eV. The relationship between the ionic conductivity and specific features of the atomic structure of cancrinites is discussed.

A first principle study of the phase stability, ion transport and substitution strategy for highly ionic conductive sodium antipervoskite as solid electrolyte for sodium ion batteries

Materials in the Na-rich antiperovskite family are promising candidates as solid electrolytes (SEs) for all-solid-state Na-ion batteries (NIBs). In this work, we carry out ab-initio calculations to study various properties of Na3OCl, namely the formation energies of various neutral defect pairs, the defect hopping barriers, the solution energies of high valence alkali earth metal substitutes to the Na atoms, and the effect of such substitution to the Na migration. While the introduction of alkali earth metal ions increases the Na vacancy concentration, the activation energy of Na transport also increases. Furthermore, we identify Ca as the most promising alkali earth metal to be doped into Na3OCl due to its low binding energy and relatively small impact on the migration barrier. Our work provides a theoretical framework for further improving the Na conductivity of materials in the antiperovskite family for all-solid-state NIBs.

Transepithelial Na and Urea Transport Pathways in Rat Inner Medullary Thin Limbs of Henle's Loop

Identification of key transport pathways for Na and urea in thin limbs of Henle's loops will further explain how solute recycling and countercurrent mechanisms are integrated to produce the corticomedullary osmotic gradient. We studied transepithelial Na and urea fluxes by in vivo microperfusion of papillary descending and ascending thin limbs (DTLs and ATLs, respectively) and by in vitro microperfusion of isolated DTLs and ATLs from the upper and lower 50% of the inner medulla (IM). In vitro studies have shown that transepithelial water permeability (Pf) is high in DTLupper and low in DTLlower, ATLupper and ATLlower. In vivo microperfusion studies confirmed the low Pf in papillary DTLs and ATLs. Mean transepithelial Na and urea permeabilities (PNa, Purea) with in vitro lumen perfusion rates of ~30 nl/min in DTLupper were ~60 E‐5 cm/sec and in DTLlower and ATL were ~350 to 450 E‐5 cm/sec; Na and urea fluxes in DTLlower are directly proportional to lumen perfusion rates between 5 to 30 nl/min. In vivo microperfusion studies confirmed the high PNa and Purea in papillary DTLs and ATLs. With in vitro microperfusion, Purea in DTLupper and DTLlower was not inhibited by peritubular phloretin (0.25 mM) indicating that urea fluxes occur independently of known facilitated urea transporters such as UT‐A1, UT‐A2 or UT‐A3. Furthermore, Purea in DTLlower was not inhibited by ouabain (10 mM) or by a lumen‐to‐bath Na concentration gradient (143 mM/lumen and 0 mM/bath) indicating the absence of Na‐dependent urea transport. On the other hand, Purea in DTLupper and DTLlower were almost completely inhibited by peritubular lanthanum (5 mM), with Purea recovering in both segments following 20 min lanthanum washout. Lanthanum (5 mM) also completely inhibited PNa in DTLlower; however, PNa remained completely inhibited following 20 min washout. Activation energy for transepithelial Na and urea transport determined by in vitro microperfusion during 37°‐ to −16° C temperature transitions was found to be low in DTLupper (~1–2 kJ/mol) compared to DTLlower and ATL (~13 kJ/mol). Urea transport in DTLupper and Na and urea transport in DTLlower and ATL likely occur in large part, by way of a plasma membrane or paracellular channel‐like pathway. The distinctive transport characteristics suggest that there are different mechanisms involved with PNa and Purea in upper and lower DTLs, respectively.Support or Funding InformationNIDDK DK083338 (TP)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Temperature Dependent Electron Transport Properties of Gold Nanoparticles and Composites: Scanning Tunneling Spectroscopy Investigations.

Scanning tunneling spectroscopy (STS) is used for investigating variations in electronic properties of gold nanoparticles (AuNPs) and its composite with urethane-methacrylate comb polymer (UMCP) as function of temperature. Films are prepared by drop casting AuNPs and UMCP in desired manner on silicon substrates. Samples are further analyzed for morphology under scanning electron microscopy (SEM) and atomic force microscopy (AFM). STS measurements performed in temperature range of 33 °C to 142 °C show systematic variation in current versus voltage (I-V) curves, exhibiting semiconducting to metallic transition/Schottky behavior for different samples, depending upon preparation method and as function of temperature. During current versus time (I-t) measurement for AuNPs, random telegraphic noise is observed at room temperature. Random switching of tunneling current between two discrete levels is observed for this sample. Power spectra derived from I-t show 1/f2 dependence. Statistical analysis of fluctuations shows exponential behavior with time width τ ≈ 7 ms. Local density of states (LDOS) plots derived from I-V curves of each sample show systematic shift in valance/conduction band edge towards/away from Fermi level, with respect to increase in temperature. Schottky emission is best fitted electron emission mechanism for all samples over certain range of bias voltage. Schottky plots are used to calculate barrier heights and temperature dependent measurements helped in measuring activation energies for electron transport in all samples.

Аnionic doping (F−, Cl−) as the method for improving transport properties of proton-conducting perovskites based on Ba2CaNbO5.5

The novel Cl−-doped compound based on oxygen deficient double perovskite Ba2CaNbO5.5 was synthesized Ba2CaNbO5.48Cl0.05 and its structure, thermal properties, hydration behavior and electrical properties have been investigated. It was found that introduction of Cl− ions leads to the increasing of oxygen ion and proton conductivities. The appearance of donor defect Clo (or Fo) decreases the activation energy for oxygen ion transport and increases the mobility of oxygen vacancies due to electrostatic repulsion between the positive charged defects Vo and Clo (Fo). It was shown that Cl−-doping decreases proton concentration but enhances proton conductivity due to significant increase in proton mobility.

Study on the Crystallization Activation Energy of Poly (L-lactic acid) Nucleated with P-tert-butylcalix[8]arene

The crystallization activation energy (Δ E) of a polymer comprises the nucleation activation energy Δ F and the transport activation energy Δ E*. In this paper, the Δ E of poly (L-lactic acid) (PLLA) nucleated with nucleating agent p- tert-butylcalix[8]arene (tBC8) was calculated. The results showed that the Δ E of nucleated PLLA was 165.97 kJ/mol, which is higher than that of pure PLLA. The reason why Δ E of PLLA increased when incorporating nucleating agent was studied. The increment of glass transition temperature ( Tg) for nucleated PLLA revealed that the polymer chain mobility was restricted by tBC8, which was considered as the reason for the increase of Δ E*. Further, polyethylene glycol (PEG) was added to improve the chain mobility, thus eliminated the variation of the transport activation energy Δ E* caused by tBC8. Then the effect of the increment of crystallization temperature range on the increase of Δ F was also taken into consideration. It was concluded that both decreasing the mobility of chain segments and increasing the crystallization temperature range caused an increase of Δ E for PLLA/tBC8.

Water Permeability across the Droplet Bilayer Reveals Interaction between Cholesterol and Polyunsaturated Lipids

Cholesterol can be the major component of total lipid in mammalian cellular membranes, hence the knowledge of its association with lipid bilayer membranes will be essential to understanding membrane structure and function. A Droplet Interface Bilayer (DIB) provides a convenient and reliable platform through which permeability coefficient and activation energy for water transport across the membrane can be determined. In this paper, we present the effect of acyl chain structure in amphiphilic monoglycerides in the presence and absence of cholesterol on the permeability of water across DIB membranes composed of these monoglycerides, where the acyl chain length, number of double bonds, and the position of double bond are varied systematically along the acyl chains, at two different cholesterol concentrations. Our systematic studies show dramatic sensitivity and selectivity of specific interaction of cholesterol with the monoglyceride bilayer having structural variations in acyl chain compositions. Our findings allow us to delineate the exquisite interplay between membrane properties and structural components and understand the balanced contribution of each. This successful demonstration will provide important insights into the factors determinative of passive membrane permeability in a wide variety of biologically relevant systems.

Influence of Nonstoichiometry on Proton Conductivity in Thin-Film Yttrium-Doped Barium Zirconate.

Proton-conducting perovskites have been widely studied because of their potential application as solid electrolytes in intermediate temperature solid oxide fuel cells. Structural and chemical heterogeneities can develop during synthesis, device fabrication, or service, which can profoundly affect proton transport. Here, we use time-resolved Kelvin probe force microscopy, scanning transmission electron microscopy, atom probe tomography, and density functional theory calculations to intentionally introduce Ba-deficient planar and spherical defects and link the resultant atomic structure with proton transport behavior in both stoichiometric and nonstoichiometric epitaxial, yttrium-doped barium zirconate thin films. The defects were intentionally induced through high-temperature annealing treatment, while maintaining the epitaxial single crystalline structure of the films, with an overall relaxation in the atomic structure. The annealed samples showed smaller magnitudes of local lattice distortions because of the formation of proton polarons, thereby leading to decreased proton-trapping effect. This resulted in a decrease in the activation energy for proton transport, leading to faster proton transport.

Effects of Acyl Chain Unsaturation on Activation Energy of Water Permeability across Droplet Bilayers of Homologous Monoglycerides: Role of Cholesterol.

Cholesterol is an important component of total lipid in mammalian cellular membranes; hence, the knowledge of its association with lipid bilayer membranes will be essential to understanding membrane structure and function. A droplet interface bilayer (DIB) provides a convenient and reliable platform through which values for permeability coefficient and activation energy of water transport across the membrane can be extracted. In this study, we investigated the effect of acyl chain structure in amphiphilic monoglycerides on the permeability of water across DIB membranes composed of cholesterol and these monoglycerides, where the acyl chain length, number of double bonds, and the position of double bond are varied systematically along the acyl chains. To elucidate the role of cholesterol in these membranes, we investigated its influence on water permeability and associated activation energies at two different cholesterol concentrations. Our systematic studies show dramatic sensitivity and selectivity of specific interaction of cholesterol with the monoglyceride bilayer having structural variations in acyl chain compositions. Our findings allow us to delineate the exquisite interplay between membrane properties and structural components and understand the balanced contribution of each.

The effect of polymer molecular weight on the performance of PTB7-Th:O-IDTBR non-fullerene organic solar cells

Activation energy for charge transport, carrier concentration and recombination rate are identified to strongly affect the device characteristics.