Charge Diffusion Research Articles

Substitution-triggered broken symmetry of cobalt tungstate boosts redox kinetics in pseudocapacitive storage

Achieving delicate broken symmetry enables significant modification of crystals, from which a variety of property or performance modulation can be expected. Here, we report that the electrochemical performance of wolframite-type CoWO 4 is significantly boosted using a Mo-substituted-W strategy. Experimental and theoretical analyses reveal that molybdenum substitution achieves WO 6 coordination broken symmetry effectively, and it renders electroactive cobalt centers more polar, thus promoting the charge diffusion kinetics. Additionally, the enhancement of OH − adsorption energy can also alter the pseudocapacitive charge storage property, which significantly reinforces ion diffusion kinetics. As a result, the optimized molybdenum substitution (20 mol%) in CoWO 4 exhibits a specific capacitance of 840 F g −1 at 1 A g −1 , as well as a maximal energy density of 33.68 Wh kg −1 at power density of 800 W kg −1 . Inspired by manipulating symmetry of crystals, our findings may provide insights into the origin of the substitution-promoted enhanced reaction kinetics. • Mo substitution breaks the symmetry of WO 6 coordination • Mo substitution increases the polarity of electroactive Co centers • Local substitution of Mo boosts redox kinetics, rate capability, and adsorption energy • Partial substitution of Mo optimizes the electrochemical properties of CoWO 4 Delicate symmetry modification can significantly alter the properties of crystals. Huang et al. report that a symmetry-broken CoWO 4 crystal structure can be achieved by using a molybdenum substitution strategy, thus enhancing pseudocapacitive storage.

Dielectric relaxation properties, and AC conductivity of Erbium(III)-Tris(8-hydroxyquinolinato) nanostructured films

Thin films of Erbium (III)-Tris (8-hydroxyquinolinato (ErQ3) were accomplished by thermal evaporating procedure. The thermal stability of ErQ3 powder was studied by the differential scanning calorimeter (DSC). The SEM image of ErQ3 thin film revealed that the surface morphology of ErQ3 is composed from several of islands structure, meanwhile each island look like algae-shape. The variation of the dielectric real and imaginary parameters versus temperature and frequency were discussed. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The activation energy of the relaxation process (ΔE) was found to be 0.428 eV. In addition, the density of localized states at Fermi levels N(Ef) was estimated to be 1.33×1018eV−1cm−3. AC conductivity at various frequencies and temperatures was investigated. At high frequency regime, the AC conductivity behavior was explained by Jonscher formalism. The charge transport mechanism was found to be controlled by the barrier hopping model (CBH). The decrease of the potential barrier height (Wm) as temperature increases unveils the growing of diffusion charges as the temperature increases. The decrease of the activation energy of the AC conductivity (ΔEAc) as the frequency increases confirms the effect of the applied frequency in the enhancement of the eletrons hopping between the two nieghoburing sites. Overall, the relatively small value of the potential barrier height (Wm) and the extensive localized electronic states encourages the utilizing of ErQ3 in designing the solar cell units.

Coupled layer construction for synthetic Hall effects in driven systems

Quasiperiodically driven fermionic systems can support topological phases not realized in equilibrium. The fermions are localized in the bulk, but support quantized energy currents at the edge. These phases were discovered through an abstract classification, and few microscopic models exist. We develop a coupled layer construction for tight-binding models of these phases in $d\in\{1,2\}$ spatial dimensions, with any number of incommensurate drive frequencies $D$. The models exhibit quantized responses associated with synthetic two- and four-dimensional quantum Hall effects in the steady state. A numerical study of the phase diagram for $(d+D) = (1+2)$ shows: (i) robust topological and trivial phases separated by a sharp phase transition; (ii) charge diffusion and a half-integer energy current between the drives at the transition; and (iii) a long-lived topological energy current which remains present when weak interactions are introduced.

Sodium Ion Storage in Na4MnV(PO4)3@C Free‐Standing Electrode

AbstractTo enhance the energy density of batteries and explore intrinsic charge storage mechanism of the active materials, it is important to reduce or eliminate the use of non‐active materials in electrodes, such as binder and conductive additives. Herein, free‐standing Na4MnV(PO4)3@C (F‐NMVP@C) fiber membrane is fabricated and directly used as a sodium‐ion battery (SIB) cathode. In situ X‐ray diffraction reveals that the V3+/V4+ redox reaction occurs through a solid‐solution reaction while a two‐phase Mn2+/Mn3+ redox reaction is identified, and both are highly reversible. Meanwhile, ex situ electrochemical impedance spectroscopy reveals that both the ion diffusion coefficient and charge transfer resistance of F‐NMVP@C change reversibly during the Na+ intercalation/de‐intercalation. Battery full cells are assembled based on the free‐standing F‐NMVP@C cathodes and F‐Sb@C anodes, which manifests a high energy density (293 Wh kg−1) and good cyclability (87.5% after 100 cycles at 1 C). The high‐performance free‐standing cathodes and anodes shed light on the development of flexible SIBs.

Heterostructures Stimulate Electric-Field to Facilitate Optimal Zn2+ Intercalation in MoS2 Cathode.

The electric-field effect is an important factor to enhance the charge diffusion and transfer kinetics of interfacial electrode materials. Herein, by designing a heterojunction, the influence of the electric-field effect on the kinetics of the MoS2 as cathode materials for aqueous Zn-ion batteries (AZIBs) is deeply investigated. The hybrid heterojunction is developed by hydrothermal growth of MoS2 nanosheets on robust titanium-based transition metal compound ([titanium nitride, TiN] and [titanium oxide, TiO2 ]) nanowires, denoted TNC@MoS2 and TOC@MoS2 NWS, respectively. Benefiting from the heterostructure architecture and electric-field effect, the TNC@MoS2 electrodes exhibit an impressive rate performance of 200 mAh g-1 at 50mA g-1 and cycling stability over 3000 cycles. Theoretical studies reveal that the hybrid architecture exhibits a large-scale electric-field effect at the interface between TiN and MoS2 , enhances the adsorption energy of Zn-ions, and increases their charge transfer, which leads to accelerated diffusion kinetics. In addition, the electric-field effect can also be effectively applied to TiO2 and MoS2 , confirming that the concept of heterostructures stimulating electric-field can provide a relevant understanding for the architecture of other cathode materials for AZIBs and beyond.

Effect of charge and anisotropic diffusivity on ion exchange kinetics in nuclear waste form materials

Motifs of radionuclide absorption particles (absorbers or fillers) for the nuclear waste treatment usually have crystal structures with nano-sized tunnels for fast ion diffusion. On the other hand, the accumulation of ions generates an electric field which affects the ion diffusion. Therefore, the strong anisotropic kinetic properties and the electric field affect ion exchange kinetics, especially in an assembly of these particles which may block the fast diffusion tunnels for each other. In this work, we developed a mesoscale model to describe the effect of anisotropic kinetic properties and electric field on ion exchange kinetics. With the model we simulated the effect of anisotropic diffusivity, electrochemical potential, particle morphology, size and aggregation on ion exchange kinetics during batch experiments. It is found that (1) ion exchange results in charge accumulation inside the particle because different ions have different diffusivities and different diffusion driving forces. The electric neutrality is not preserved; (2) the electric field speeds up the slower diffusion ions (either uptake or release) and slows down the faster diffusion ions to reduce charge accumulation and maintains charge neutrality; (3) the ion exchange becomes very slow at the later stages because (a) diffusion driving force (electrochemical gradient, Cs+ concentration in the solution and Na+ inside the particle) continuously decreases, as observed in batch experiments; and (b) the diffusivity decreases due to the Cs+ concentration dependence of ion diffusivity. This can explain the observed experimental phenomena that the radionuclide capacity usually cannot be reached; (4) for needle-like particle and their clusters, both surface area and diffusion distance along the direction with the fastest diffusivities have significant impact on the ion exchange kinetics.

Synthesis of Yttrium Doped Barium Zirconate/Cerate Electrolyte Materials and Densification Using Conventional and Cold-Sintering Processes

Compared to high temperature SOEC usually based on Yttrium stabilized Zirconia electrolytes, intermediate temperature PCEC allows the production of water free hydrogen and a better chemical stability. Proton conducting perovskite specific materials, such as Barium Indates1, Zirconate or Cerates2 are nearly commercial electrolytes for such devices.This study focuses on the synthesis the characterization and the densification of the BaZr1-xCexY0.1O3- δ 3 powder. At intermediate temperature and under humid atmosphere, hydration process allows diffusion of protonic charges. Such electrolyte material combines a low thermal expansion coefficient and a high protonic conductivity. Two specific stoichiometry’s have been studied, Cerium rich BaZr 0.3 Ce 0.6 Y0.1O3- δ (BZCY361) and Zirconium rich BaZr 0.7 Ce 0.2 Y0.1O3- δ (BZCY721). BZCY361 shows at 550°C, a conductivity level of 2.10- 2 S.cm- 1. However, despite its high protonic conductivity, the cerium rich phase is not stable at high temperature and is torn apart in presence of carbon dioxide.BaZr1-xCexY0.1O3- δ powder has been synthetized by combustion reaction based on nitrate precursors and glycine as organic complexing/fuel agent. The fuel/oxidizer (nitrates) ratio, which is a key parameter4, has been optimized in order to obtain the best purity and crystallinity. The powder is then milled and calcined. The single-phase electrolyte powder is conventionally shaped into pellets and densified A minimal temperature of 1600°C is necessary to obtained a density of 90-95%. In order to reduce the sintering temperature, an intermediate sintering step called "Cold Sintering Process"5 (CSP) has been investigated. In this technic, derived from the hydrothermal method, BCZY powder mixed with a small volume of liquid phase (3-30 wt%) is simultaneously pressed (at 50 to 500 MPa) and heated during a short time period (1-60 min) at low temperatures (100-200°C), leading to dense pellets.In regards to design a complete cell based on this electrolyte, EIS has been performed under hydrogen and air atmosphere. The electrochemical measurements of the samples provided by the different protocols and stoichiometry’s have been compared in order to determine the impact of the CSP and stoichiometry parameters on the ionic conductivity of the material.Acknowledgment: This study, included in the PhD of P. Castellani, was made possible with support from the Franco German ANR-BMBF project (Grant No. ANR-19-ENER-0003-12 [1] Quarez, Eric, Samuel Noirault, Annie Le Gal La Salle, Philippe Stevens, et Olivier Joubert. « Evaluation of Ba2(In0.8Ti0.2)2O5.2−n(OH)2n as a Potential Electrolyte Material for Proton-Conducting Solid Oxide Fuel Cell ». Journal of Power Sources 195 (15), 4923-27 (2010) [2] Thabet, K., Le Gal La Salle, A., Quarez, E., and Joubert, O. “Protonic-Based Ceramics for Fuel Cells and Electrolyzers,” Solid Oxide-Based Electrochemical Devices, Elsevier, pp. 91–122 (2020) [3] Thabet, K., Devisse, M., Quarez, E., Joubert, O., and Le Gal La Salle, A. “Influence of the Autocombustion Synthesis Conditions and the Calcination Temperature on the Microstructure and Electrochemical Properties of BaCe0.8Zr0.1Y0.1O3− δ Electrolyte Material,” Solid State Ionics, 325, pp. 48–56, (2018) [4] Varma, A., Mukasyan, A. S., Rogachev, A. S., and Manukyan, K. V., “Solution Combustion Synthesis of Nanoscale Materials,” Chem. Rev., 116(23), pp. 14493–14586 (2016) [5] Guo, H., Baker, A., Guo, J., and Randall, C. A., “Cold Sintering Process: A Novel Technique for Low‐Temperature Ceramic Processing of Ferroelectrics,” J. Am. Ceram. Soc., 99(11), pp. 3489–3507 (2016) Figure 1

(Digital Presentation) Resistive Switching and Brain-Inspired Computing in Perovskite Nanowires and Quantum Wires

In the past decade, halide perovskites (HPs) have shot to fame in the genre of optoelectronics and photovoltaics owing to their large absorption co-effcient, high color purity, tunable bandgap and long charge diffusion lengths. Besides these traits, HPs also possess innumerable charge transport pathways, inherent hysteresis, high charge-carrier and ionic mobilities which render them as ideal candidates for resistive random access switching memories (RRAMs). However owing to material and electrical instability associated with HP thin-film devices, the figures-of-merits (FOMs) namely retention, endurance and switching speed were not up to the state of-the-art standard until recently. In order to revolutionize HP Re-RAMs we devised a unique device structure where we replaced the thin-film architecture with vertically aligned high density HP nanowires and quantum wires embedded in a porous alumina membrane (PAM) sandwiched between metallic silver and aluminum contacts. The excellent passivation provided by the PAM imparted the requisite electrical and material stability to the environmentally delicate HPs by drastically reducing the surface diffusion pathways and thereby thwarting the moisture induced attacks. Extrapolated retention time as high as 28.3 years and measured device endurance of a million cycles were obtained. Utilizing the single crystalline HP nanowires and quantum wires and their associated high ionic and electronic mobilities, switching speed as fast as 100 ps was also obtained. These FOMs represent record values for HP RRAMs ever reported. Furthermore a 14 nm lateral size HP quantum wire RRAM cell was fabricated and a cross-bar device architecture with a unique sneaky path mitigation scheme were developed, which successfully exhibited the scalability potential of our devices. We further coupled the optoelectronic and switching behaviors and were able to obtain optical programmability among the low resistance states. Besides data storage, the HP nanowires and quantum wires were employed in developing neuromorphic devices enabled with low power and high precision computing capabilities. Specifically, we obtained robust multi-level states in two types of brain-inspired devices capable of performing analog processing tasks by using silver as the top electrode and precisely controlling the current injection in the monocrytalline switching medium and by using indium doped tin oxide as the top electrode and inducing a novel valence change mechanism in the HP nanowires triggering the gradual conductance change. All in all, our nanowire and quantum wire devices propel HP RRAMs to the state-of-the-art standard in multifarious applications concerning future data storage and neuromorphic computing.

Coal-Based Nanoporous Carbon Electrode for High-Performance Supercapacitor: Surface and Diffusion Charge Kinetics in Aqueous and Non-Aqueous Electrolytes

South Africa generates around 60 million tonnes of coal discards each year, with over 1.2 billion tonnes landfilled in discard dumps and slurry ponds. The huge quantity of coal discards generated within the past decades, which is a significant liability to the mining industry and the environment, presents an opportunity to reuse this resource. This study investigated the potential of nanoporous carbon material from coal discard via KOH activation for use as electrode material in supercapacitors. Hierarchical morphology is seen via scanning electron microscopy (SEM). Raman spectroscopy reveals structural defects, X-ray Diffraction spectroscopy (XRD) confirms the material's amorphous nature, and N2 at 77k adsorption reveals a carbon material with high porosity and a surface area of 1424 m2/g.Electrochemical analysis reveals that the charge storage mechanism of the material is surface-controlled (non-faradaic) in the non-aqueous (TEABF4/ACN) electrolyte and diffusion-controlled (faradaic) mechanism in the aqueous (Na2SO4) electrolyte. The material has a higher specific capacitance (162 F/g) and cycling stability of 87.1% capacitance retention after 5000 cycles in Na2SO4. The material exhibits a better rate capability in TEABF4/ACN with 92.3% capacitance retention. A symmetrical two-electrode device using Swagelok T-cell assembly achieves energy densities of 15.5 and 10.4 Wh/kg in Na2SO4 and TEABF4/ACN, respectively, and a power density of 100 W/kg in both electrolytes. The variation in the capacitive performance of the material in both electrolytes is due to differences in electrolyte ion size, ionic conductivity, and pore structure. This study not only establishes a link between the structure of coal-based nanoporous carbon and its electrochemical performance in both electrolytes but also demonstrates the potential of coal-based functional materials for sustainable energy storage.

ALD-fabricated two-dimensional SnO2-In2O3n-n nanohybrid electrode for electrochemical supercapacitors

Fabrication of thin-film heterostructured electrodes with thickness below 10.0 nm is of great importance for the development of high-performance electrochemical supercapacitors (ESCs) with great capabilities. This is because such electrodes with uniform thicknesses enable fast electrochemical responses during charging/discharging ascribed to their short charge and ion diffusion lengths. In this study, two-dimensional (2D) SnO2-In2O3 heterostructures with a thickness of ∼7.84 nm was fabricated on Au/SiO2/Si wafers by the atomic layer deposition (ALD) technique for ESCs application. Various spectroscopic and microscopic analyses demonstrated the formation of 2D SnO2-In2O3 heterojunction with high purity, crystallinity and homogeneous morphology. Cyclic voltammetry (CV) measurements revealed the pseudocapacitive Faradaic redox reactions with good reversibility for 2D SnO2-In2O3 heterostructure. The heterostructured electrodes demonstrated excellent super-capacitive performance with high specific capacitance (Cs) up to 1048.25 and 757 F g−1 at the scan rate and the current density of 10 mV s−1 and 12 A g−1, respectively. Accordingly, a high energy density of 51.55 Wh kg−1 is attained at 12 A g−1. The high super-capacitive performance of these heterostructures can be attributed to the improved redox activity and short ion diffusion length of the SnO2-In2O3 nanohybrid thin-film. The electrodes also demonstrated great electrochemical stability with the Cs retention of 96.15% even after 5000 charge/discharge cycles.

A thermostable ionic liquid electrolyte for wide-temperature window supercapacitor

The high-temperature supercapacitors have attracted growing attentions because the improved charge diffusion kinetics and ion conductivity of the electrolytes at elevated temperatures cause high capacitances. However, the state-of-the-art aqueous and/or anhydrous electrolytes always suffer from water or organic solvent evaporation, poor thermal stability and toxicity. We presented here a wide-temperature window supercapacitor made with an activated carbon electrode, a ceramic membrane separator as well as an electrolyte containing 1-methylimidazolium trifluoromethanesulfonate ([MIm][OTf]) ionic liquid and ethylene glycol (EG) organic solution of potassium hydroxide (KOH) ([MIm][OTf]/KOH/EG). By studying the impacts of temperature on capacitance, a maximized specific capacitance of 289 F g − 1 was achieved at 130 °C. Moreover, the champion supercapacitor presented an outstanding charging/discharging stability over 1500 cycles at 130 °C. The high capacitance along with long-term stability suggest that the ionic liquid electrolyte is prospective for wide-temperature window supercapacitors.

Graphene oxide microrolls as high- content Si carriers boosting Li-ion storage

As attractive anode materials of lithium-ion batteries, both microsized and nanosized silicon particles have been investigated widely, but each has lots of insurmountable problems to restrict their practical applications. In this work, combining the advantages of microsized and nanosized Si particles, we reported a new thought for constructing micrometer-sized Si/C particles by embedding Si nanoparticles into graphene oxide (GO)-based mirorolls. Differing to the traditional spherical shape, the resulted Si/C microrolls exhibit a unique elastic coil structure with opening ends, facilitating the stress buffer and fast charge diffusion. Besides, in order to maintain the stability of Si nanoparticles in microrolls, we chose the elastic and deformable liquid metal (LM) as the “cloth”, and sodium alginate (SA) as the “thread”, successfully tailor a novel “tight suit” for each Si nanoparticle by a facile self-assembly process. Thanks to the double protection of the conductive-elastic LM-SA coating and the microroll architecture, the resulted Si@LM-SA@GO microroll anode not only has a high Si content of 69 %, a high tap density of 0.62 g cm−3 and a high initial coulombic efficiency of 85.1 %, but also exhibits a superior volumetric capacity of 2506 mAh cm−3, and a superior cycling performance of 660 mAh cm−3 after 500 cycles at 2 A g−1. The full cell constructed using a LiNiCoMnO2 cathode can achieve a high reversible capacity of 150 mAh g−1 at 1C after 250 cycles, delivering a high-energy density of 510 Wh kg−1.

Numerical study of the effect of temperature and H2O concentration on the electrostatic precipitator characteristics at high temperatures

In this study, a numerical model of an electrostatic precipitator (ESP) suitable for high-temperature flue gas was established using COMSOL Multiphysics, and the effects of temperature and H 2 O concentration on the high-temperature ESP performance were studied. The results showed that, at the same voltage, increasing the temperature increased the negative ion density, thereby improving the particle charge and collection efficiency. However, increasing the temperature led to a decrease in the maximum operating voltage of the ESP, which reduced the negative ion density and electric field intensity at the maximum operating voltage and weakened the diffusion and field charges of the particles, leading to a further decrease in the maximum collection efficiency. Increasing the H 2 O concentration in the flue gas increased the negative ion density and, thus, enhanced the diffusion charge of the particles, which helped improve the collection efficiency. • A modified ESP model suitable for high temperature gas was established. • The plasma model was used to simulate corona discharges in the ESP. • The effect of temperature on ESP performance was studied numerically. • The effect of H 2 O concentration in flue gas on ESP performance was studied.

High time-resolution measurements of ultrafine and fine woodsmoke aerosol number and surface area concentrations in biomass burning kitchens: A case study in Western Kenya.

Indoor air pollution associated with biomass combustion for cooking remains a significant environmental health challenge in rural regions of sub-Saharan Africa; however, routine monitoring of woodsmoke aerosol concentrations continues to remain sparse. There is a paucity of field data on concentrations of combustion-generated ultrafine particles, which efficiently deposit in the human respiratory system, in such environments. Field measurements of ultrafine and fine woodsmoke aerosol (diameter range: 10-2500 nm) with field-portable diffusion chargers were conducted across nine wood-burning kitchens in Nandi County, Kenya. High time-resolution measurements (1Hz) revealed that indoor particle number (PN) and particle surface area (PSA) concentrations of ultrafine and fine woodsmoke aerosol are strongly temporally variant, reach exceedingly high levels (PN > 106 /cm3 ; PSA > 104 μm2 /cm3 ) that are seldom observed in non-biomass burning environments, are influenced by kitchen architectural features, and are moderately to poorly correlated with carbon monoxide concentrations. In five kitchens, PN concentrations remained above 105 /cm3 for more than half of the day due to frequent cooking episodes. Indoor/outdoor ratios of PN and PSA concentrations were greater than 10 in most kitchens and exceeded 100 in several kitchens. Notably, the use of metal chimneys significantly reduced indoor PN and PSA concentrations.

Supercapacitive performance of exfoliated graphitic carbon nitride nanoflakes

Recently, Exfoliated graphitic carbon nitride (E-gCN) has drawn significant interest in the field of energy generation and storage. In this study, exfoliated graphitic carbon nitride nanoflakes are synthesized by condensation followed by ultrasonic exfoliation. The supercapative behavior of exfoliated graphitic carbon nitride is analyzed. Structural analyses confirm the formation of thiazine and heptazine heterocycles. Scanning electron microscopy image shows flake-like morphology. The E-gCN exhibit the specific capacitance of 160 F g−1 at 1 A g−1 and retains 96.2% capacity at 3000 cycles. The presence of nitrogen in the two-dimensional layered structure significantly increases the conductivity and alters the electronic structure. The nano-flake morphology increases the charge diffusion kinetics, which improve the charge storage mechanism.

Synthesis of Yttrium Doped Barium Zirconate/Cerate Electrolyte Materials and Densification Using Conventional and Cold-Sintering Processes

Compared to high temperature solid oxide electrolysis cell, usually based on Yttrium stabilized Zirconia electrolytes, intermediate temperature proton conducting electrolysis cell, allows the production of water free hydrogen and a better chemical stability. Proton conducting perovskite materials, such as Barium Indates, Zirconates or Cerates are nearly commercial electrolytes for such devices. At intermediate temperature and under humid atmosphere, hydration process allows diffusion of protonic charges. Such electrolyte material combines a low thermal expansion coefficient and a high protonic conductivity. and The Zirconium rich material BaZr0.7Ce0.2Y0.1O3-δ that shows a conductivity around 10-2 S.cm-1 at 500°C will be compared to the Cerium rich BaZr0.3Ce0.6Y0.1O3-δ material that shows conductivities around 10-4 S.cm-1 at the same temperature.

Multiplying Energy Storage Capacity: In Situ Polypyrrole Electrodeposition for Laser-Induced Graphene Electrodes

Scalability and automation are two cornerstones for advanced manufacturing where laser-induced graphene (LIG) can play a key role. However, it is well known that LIG, employed as an electrode material for electrochemical storage devices, has a severely limited energy storage capability, thus presenting a major roadblock to mass commercial adoption. Herein, a technique based on the in situ electrodeposition of polypyrrole (PPy) onto three-dimensional (3D) porous LIG (LIG@PPy) is proposed for overcoming the inherent charge storage limit of LIG. For demonstration, zinc-ion hybrid microsupercapacitors (ZHMSCs) have been realized by integrating LIG@PPy cathodes with Zn anodes. As a key advantage, the conformal deposition of PPy with high specific capacity significantly enhances the charge storage capacity of the LIG skeleton and improves conductivity while maintaining the structural integrity of the porous structure to ensure fast charge diffusion kinetics. Further benefiting from the use of multivalent ions and asymmetrical electrodes, the prototyped ZHMSC exhibits a wide voltage window (1.7 V) and a remarkable areal capacitance/energy density (149 mF cm–2/54 μWh cm–2), which represents a 200× enhancement from the pristine LIG counterpart. This work provides a simple strategy for unlocking the full energy storage potential of LIG without sacrificing any of its existing advantages, overcoming a major bottleneck that had plagued LIG as a practical cathode material for microsupercapacitors and other energy storage devices.

Lead Halide Perovskite Quantum Dots for Photovoltaics and Photocatalysis: A Review

Lead halide-based perovskite quantum dots (PQDs) have recently emerged as an important class of nanocrystal (NC) materials for optoelectronic and photoelectrochemical applications. Thanks to their intriguing features including tunable band gap, narrow emission, high charge carrier mobility, remarkable light-absorbing factors, and long charge diffusion length, there has been a surge in research on lead halide-based PQDs and their applications. In this review, we showcase the fundamentals of PQDs and two principal applications including PQD solar cells (PQDSCs) and photocatalytic conversion. First, a thorough discussion on PQDSCs, their structure, surface treatment, and interface engineering along with their recent progress are presented. It is highlighted that the improvement of the efficiency of PQDSCs from below 10% to beyond 16% in a matter of a few years has turned them into promising candidates for future SC applications. Subsequently, the application of PQDs in photocatalytic reactions such as hydrogen production, CO2 reduction, and organic compounds’ degradation is summarized. Not to mention that, despite the remarkable properties of PQDs in SCs and photocatalysis, the inferior stability of PV devices based thereon under operation as well as their poor tolerance under air, water, light, and heat impede their widespread application. For this, the practical efforts and possible solutions are extensively addressed. Finally, an outlook is provided, addressing further merits, and demerits of each application as well as prospective opportunities.

Kinetics of hydrodynamic pions in chiral perturbation theory

We determine the kinetic coefficients of ultrasoft pions using chiral perturbation theory at finite temperature close to the chiral limit. This is used to compute the axial charge diffusion and damping coefficients in the hydrodynamic effective theory for these pion waves. We show that to provide a leading order answer for these coefficients one needs to explore the dynamics of hard, soft, and ultrasoft pion modes, which are represented microscopically by the appropriate kinetic and hydrodynamic descriptions..

Fabrication of CuFe2O4@g-C3N4@GNPs nanocomposites as anode material for supercapacitor applications

The aim of this study was to synthesize CuFe2O4 together with g-C3N4 and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe2O4 was successfully synthesized together with g-C3N4 and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm2 at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm2 and 300 mW/cm2, respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications.