Charge Diffusion Research Articles

Metal-organic framework derived Co1-xS@C nanoboxes for long-life Na+ storage

Transition metal sulfides appear excellent electrochemical properties in the realm of anode for sodium-ion batteries and hold significant potential for practical application in large-scale devices in the future. However, their development is hindered by inferior inherent conductivity and tremendous volume strain during discharge and charge processes. In this study, Co1-xS@C nanoboxes were synthesized utilizing Co-Co PBA as a precursor. The electrochemical sodium storage performance of Co1-xS@C electrode was characterized, revealing an extremely long-life and stable performance. At 1.0 A g−1 and 2.0 A g−1, the electrode delivered capacities of 255.8 mAh g−1 and 197.6 mAh g−1 after 5000 and 10,000 cycles respectively, with negligible capacity attenuation. The pseudo-capacitance behavior of Co1-xS@C NBs electrode in sodium storage was quantitatively calculated through CV test at varying sweep speeds. The significant contribution of pseudo-capacitance resulted in its exceptional rate capacity and electrochemical stability. Furthermore, kinetic analysis revealed that the existence of a carbon shell enhanced the Na+ diffusion kinetics and charge transfer kinetics of Co1-xS@C NBs. This strategy provides a reference for enhancing the Na+ storage performance of other transition metal sulfides.

Highly ordered structure and susceptibility to light absorption of ZnO/calcium phosphate (5%) to enhance the stability of charge diffusion as a methylene blue bond breaker

The composite Zinc oxide/calcium phosphate was successfully prepared using the sol–gel method. The structural and optical properties are observed by using x-ray Diffraction and Fourier Transform Infra-Red, respectively. The degradation of MB dye is analyzed by using Ultraviolet-Visible spectrometer. The maximum MB degradation is achieved 92.61 2.7% and shows the linear correlation to a high optical longitudinal position and enlarged d spacing. Superior photocatalytic activity is demonstrated by ZnO/CP_240 which has a consistent band gap due to its highly ordered structure and susceptibility to light absorption ability, thus triggering better charge diffusion stability. The empirical findings suggest that the introduction of CP at the atomic level into the crystal lattice of ZnO buffer generates a surplus of oxygen vacancies, thereby diminishing the strength of the MB bonding. This, in turn, facilitates the activation of lattice oxygen.

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Covalent triazine framework nanosheets (CTF NSs), an emerging class of two‐dimensional polymeric nanomaterials, have received great attention due to their abundant active sites, permanent periodic porosity, molecular structural diversity, superior chemical and thermal stability, and short charge diffusion path, thus demonstrating great potential in energy storage and conversion. More details are discussed in the review article by Xu et al. on page 301—316.image

Pattern-illumination time-resolved phase microscopy and its applications for photocatalytic and photovoltaic materials.

Pattern-illumination time-resolved phase microscopy (PI-PM) is a technique used to study the microscopic charge carrier dynamics in photocatalytic and photovoltaic materials. The method involves illuminating a sample with a pump light pattern, which generates charge carriers and they decay subsequently due to trapping, recombination, and transfer processes. The distribution of photo-excited charge carriers is observed through refractive index changes using phase-contrast imaging. In the PI-PM method, the sensitivity of the refractive index change is enhanced by adjusting the focus position, the method takes advantage of photo-excited charge carriers to observe non-radiative processes, such as charge diffusion, trapping in defect/surface states, and interfacial charge transfer of photocatalytic and photovoltaic reactions. The quality of the image sequence is recovered using various informatics calculations. Categorizing and mapping different types of charge carriers based on their response profiles using clustering analysis provides spatial information on charge carrier types and the identification of local sites for efficient and inefficient photo-induced reactions, providing valuable information for the design and optimization of photocatalytic materials such as the cocatalyst effect.

Precise analyses of photoelectrochemical reactions on particulate Zn0.25Cd0.75Se photoanodes in nonaqueous electrolytes using Ru bipyridyl complexes as a probe.

Recombination of photoexcited carriers at interface states is generally believed to strongly govern the photoelectrochemical (PEC) performance of semiconductors in electrolytes. Sacrificial reagents (e.g., methanol or Na2SO3) are often used to assess the ideal PEC performance of photoanodes in cases of minimised interfacial recombination kinetics as well as accelerated surface reaction kinetics. However, varying the sacrificial reagents in the electrolyte means simultaneously changing the equilibrium potential and the number of electrons required to perform the sacrificial reaction, and thus the thermodynamic and kinetic aspects of the PEC reactions cannot be distinguished. In the present study, we propose an alternative methodology to experimentally evaluate the energy levels of interfacial recombination centres that can reduce PEC performance. We prepare nonaqueous electrolytes containing three different Ru complexes with different bipyridyl ligands; redox reactions of Ru complexes represent one-electron processes with similar charge transfer rates and diffusion coefficients. Therefore, the Ru complexes can serve as a probe to isolate and evaluate only the thermodynamic aspects of PEC reactions. Recombination centres at the interface between a nonaqueous electrolyte and a Zn0.25Cd0.75Se particulate photoanode are elucidated using this method as a model case. The energy level at which photocorrosion proceeds is also determined.

Diffusioosmotic flow reversals due to ion-ion electrostatic correlations.

Existing theories of diffusioosmosis have neglected ion-ion electrostatic correlations, which are important in concentrated electrolytes. Here, we develop a mathematical model to numerically compute the diffusioosmotic mobilities of binary symmetric electrolytes across low to high concentrations in a charged parallel-plate channel. We use the modified Poisson equation to model the ion-ion electrostatic correlations and the Bikerman model to account for the finite size of ions. We report two key findings. First, ion-ion electrostatic correlations can cause a unique reversal in the direction of diffusioosmosis. Such a reversal is not captured by existing theories, occurs at ≈ 0.4 M for a monovalent electrolyte, and at a much lower concentration of ≈ 0.003 M for a divalent electrolyte in a channel with the same surface charge. This highlights that diffusioosmosis of a concentrated electrolyte can be qualitatively different from that of a dilute electrolyte, not just in its magnitude but also its direction. Second, we predict a separate diffusioosmotic flow reversal, which is not due to electrostatic correlations but the competition between the underlying chemiosmosis and electroosmosis. This reversal can be achieved by varying the magnitude of the channel surface charge without changing its sign. However, electrostatic correlations can radically change how this flow reversal depends on the channel surface charge and ion diffusivity between a concentrated and a dilute electrolyte. The mathematical model developed here can be used to design diffusioosmosis of dilute and concentrated electrolytes, which is central to applications such as species mixing and separation, enhanced oil recovery, and reverse electrodialysis.

Hyperbranched TEMPO-based polymers as catholytes for redox flow battery applications.

Application of redox-active polymers (RAPs) in redox flow batteries (RFBs) can potentially reduce the stack cost through substitution of costly ion-exchange membranes by cheap size-exclusion membranes. However, intermolecular interactions of polymer molecules, i.e., entanglements, particularly in concentrated solutions, result in relatively high electrolyte viscosities. Furthermore, the large size and limited mobility of polymers lead to slow diffusion and more sluggish heterogeneous electron transfer rates compared to quickly diffusing small molecules. Although a number of RAPs with varying electrolyte viscosities have been reported in the literature, the relation between the RAP structure and the hydrodynamic properties has not been thoroughly investigated. Herein, hyperbranched 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO)-based polymers intended for application as low-viscosity catholytes for RFBs are presented and the influence of the structure and the molar mass distribution on the hydrodynamic properties is investigated. A new synthesis approach for TEMPO-based polymers is established based on step-growth polymerization of a TEMPO-containing monomer using an aza-Michael addition followed by a postpolymerization modification to improve solubility in aqueous solutions. The compact structure of hyperbranched polymers was demonstrated using size-exclusion chromatography (SEC) with viscometric detection and the optimum molar mass was found based on the results of viscometric and crossover investigations. The resulting RAP revealed a viscosity of around 21 mPas at a concentration corresponding to around 1 M TEMPO-containing units, according to the calculated mass of the repeating unit, showing potential for high capacity polymer-based catholytes for RFBs. Nevertheless, possible partial deactivation of TEMPO units lowered the active TEMPO concentration of the hyperbranched RAPs. A faster diffusion and higher charge transfer rate were observed for the hyperbranched polymer compared to the previously reported linear polymers. However, in RFB tests, a poor performance was observed, which is attributed to the side reactions of the oxidized TEMPO moieties. Finally, pathways for overcoming the main remaining challenges, i.e., high loss of material during dialysis as an indication of being prone to crossover, the partial deactivation of TEMPO moieties, and the subsequent side reactions under battery conditions, are suggested.

Ion effects on minimally hydrated polymers: hydrogen bond populations and dynamics.

Compared to bulk water, the effect of ions in confined environments or heterogeneous aqueous solutions is less understood. In this study, we characterize the influence of ions on hydrogen bond populations and dynamics within minimally hydrated polyethylene glycol diacrylate (PEGDA) solutions using Fourier-transform infrared (FTIR) and two-dimensional infrared (2D IR) spectroscopies. We demonstrate that hydrogen bond populations and lifetimes are directly related to ion size and hydration levels within the polymer matrix. Specifically, larger monovalent cation sizes (Li+, Na+, K+) as well as anion sizes (F-, Cl-, Br-) increase hydrogen bond populations and accelerate hydrogen bond dynamics, with anions having more pronounced effects compared to cations. These effects can be attributed to the complex interplay between ion hydration shells and the polymer matrix, where larger ions with diffuse charge distributions are less efficiently solvated, leading to a more pronounced disruption of the local hydrogen bonding network. Additionally, increased overall water content results in a significant slowdown of dynamics. Increased water content enhances the hydrogen bonding network, yet simultaneously provides greater ionic mobility, resulting in a delicate balance between stabilization and dynamic restructuring of hydrogen bonds. These results contribute to the understanding of ion-specific effects in complex partially-hydrated polymer systems, highlighting the complex interplay between ion concentration, water structuring, and polymer hydration state. The study provides a framework for designing polymer membrane compositions with ion-specific properties.

Analyzing the charge contributions of metal-organic framework derived nanosized cobalt nitride/carbon composites in asymmetrical supercapacitors.

Metal-organic framework derived nanostructures have recently received research attention owing to their inherent porosity, stability, and structural tailorability. This work involves the conversion of zeolitic imidazolate frameworks (ZIFs) into cobalt nitride nanoparticles embedded within a porous carbon matrix (Co4N/C). The as-prepared composite shows great synergy by providing a high surface area and efficient charge transfer, showcasing outstanding electrochemical performance by providing a specific capacitance of 313 F g-1. Moreover, we meticulously conducted calculations to derive the most precise values for the surface contribution, a crucial aspect often overlooked in existing literature, thereby ensuring the reliability of our calculated measurements. Correct calculations of surface and diffusion charge contributions are necessary for evaluating the overall electrochemical performance of supercapacitors. For practical utility, we successfully assembled an asymmetrical supercapacitor employing the Co4N/carbon composite as the negative electrode that achieved an impressive energy density of 26.6 W h kg-1 at a power density of 0.36 kW kg-1. This study opens up new avenues for investigating the use of other metal nitride nanoparticles embedded in carbon structures for various energy storage applications.

Fluorine enables h-BN sheet to resist oxidizing failures in sulfur atmosphere

Corrosion is one of the most common ways in which metal components are damaged, especially under extreme conditions in the presence of sulfide ions. Due to the excellent properties of hexagonal boron nitride (h-BN) sheets, they can provide effective protection for facilities exposed to sulfur-containing atmospheres. In this paper, the thermodynamic and kinetic behavior of oxygen adsorbed on h-BN and defective D-h-BN sheets in a sulfur-containing atmosphere were performed by first-principles calculations. The adsorption energies, densities of state, band structures, differential charge densities and diffusion energy barriers were systematically investigated. The presence of sulfur reduces the diffusion energy barrier of oxygen, which accelerates the oxidative failure of h-BN sheets. Surprisingly, the F-modified h-BN sheet possesses a higher oxygen diffusion energy barrier, which explains its superior oxidation resistance. Therefore, h-BN sheets are a promising candidate as a protective material in sulfur-containing atmospheres.

Diffusely Charged Polymeric Zwitterions as Loosely Hydrated Marine Antifouling Coatings.

Polymeric zwitterions exhibit exceptional fouling resistance through the formation of a strongly hydrated surface of immobilized water molecules. While being extensively tested for their performance in biomedical, membrane, and, to a lesser extent, marine environments, few studies have investigated how the molecular design of the zwitterion may enhance its performance. Furthermore, while theories of zwitterion antifouling mechanisms exist for molecular-scale foulant species (e.g., proteins and small molecules), it remains unclear how molecular-scale mechanisms influence the micro- and macroscopic interactions of relevance for marine applications. The present study addresses these gaps through the use of a modular zwitterion chemistry platform, which is characterized by a combination of surface-sensitive sum frequency generation (SFG) vibrational spectroscopy and marine assays. Zwitterions with increasingly delocalized cations demonstrate improved fouling resistance against the green alga Ulva linza. SFG spectra correlate well with the assay results, suggesting that the more diffuse charges exhibit greater surface hydration with more bound water molecules. Hence, the number of bound interfacial water molecules appears to be more influential in determining the marine antifouling activities of zwitterionic polymers than the binding strength of individual water molecules at the interface.

Modelling Ca2+ Mobility and Dynamics in Solvent-Free Molten Salt Electrolytes for Calcium Batteries

Multivalent elements based batteries using earth-abundant minerals is a route with promises, not only from a performance but also from a supply and cost point of view; this is not the last true for calcium (Ca) batteries since Ca is the fifth most abundant element in the Earth's crust [1,2,3]. There is, however, no functional electrolyte available yet for Ca batteries, calling for early modelling to be made to map the influence of different Ca-salts and salt concentrations on electrolyte physicochemical properties such as density, viscosity, ionic conductivity, charge carrier dynamics and diffusivity [3, 4]. One particular route little trodden is molten salt electrolytes (MSEs), materials that consist of ions with different valences in direct contact with each other due to the complete absence of any solvent. In practice, MSEs are multicomponent salt mixtures with reduced melting points with respect to the ingoing components and furthermore they also expand the operating temperature range upwards as compared to conventional liquid electrolytes. Moreover, MSEs have high ionic conductivities due to their intrinsically high ionic content and ionic mobility. Additionally, MSEs exhibit wide electrochemical stability windows, non-flammability, and non-toxicity [5, 6]. We have investigated MSEs composed of Ca(FSI)2, LiFSI, NaFSI, and KFSI, by molecular dynamics (MD) simulations. Apart from the basic properties, we focus on the relative dynamical properties of the different cations in the MSEs in order to obtain a fundamental understanding of the systems’ behaviour, both globally and locally, but for natural reasons with special emphasis on the Ca2+ ions.

Proton Permeable, Oxygen Blocking, Ultrathin Al2O3 Layers for Electrocatalytic Applications

Operating zero-gap electrolyzers at current densities above 1 Acm-2 is very challenging because ohmic losses associated with ion transport across the ion exchange membrane become predominant.[1] Technically, we can reach current densities up to 10 Acm-2. However, even a 100 micrometer thin nafion membrane would lead to cell voltages over 3 V [2] due to ohmic losses. Therefore, research and experimental development efforts are still needed to enable and increase the cell efficiency at elevated current densities.Implementing an ultrathin membrane of only a few nanometers in electrolyzers will minimize ion transport (i.e. protons) losses and will enable high-throughput electrolysis at low temperatures. However, to date, there is no concept available to perform electrochemical conversions using membranes of only of a few nanometers thickness that can block molecules but permeate protons.Multiple reports have demonstrated that dense ultrathin oxide layers, i.e. SiO2, can be used as electrocatalyst coatings to increase selectivities by blocking undesired ions/molecules from reaching the electrode.[3,4] The properties of such dense ultrathin oxide layers in principle fulfil the requirements of a proton exchange membrane, being only a couple of nanometer thin.To implement a nanometer thin proton exchange membrane into an electrolysis setup and enable mechanical integrity we envision a 3D-nanotube array design as shown in Figure 1a. In the ‘inside’ of the tube we perform the Hydrogen evolution reaction, and on the ‘outside’ the water oxidation reaction. Cathode and anode are separated only by a dense ultrathin oxide layer that permeates protons but blocks oxygen.Herein, we discuss the performance of ultrathin dense and amorphous Al2O3 layers made via pulsed laser deposition (2.5 nm, 3 nm, and 5 nm) with regard to proton and oxygen permeability. Electrochemical impedance spectroscopy allows us to determine diffusion coefficients and charge transfer resistances (Figure 1b). We use state-of-the-art operando FT-IR reflection-absorption spectroelectrochemistry that enables us to probe the dynamic structural and morphological changes of the dense alumina layer over time vs. applied potential (Figure 1c). In fact, we observe that proton permeation improves over time while we can exclude dissolution of the Al2O3 layer.

Understanding the Phase Transitions in Tin Foil Electrodes for Sodium-Ion Batteries through Light Microscopy and Kinetic Analysis

Group IVA elements exhibit some interesting sodium capabilities via electrochemical alloying processes (except carbon). Among them, tin is believed to be the most promising anode candidate for sodium-ion batteries (SIBs) due to its simple fabrication and monolithic form (e.g., metallic foils).[1] Nevertheless, tin foil anodes usually fail prematurely after only a handful of cycles. This poor reversibility is reported to be largely associated with the structural collapse of tin electrodes caused by huge volume differences among various Na-Sn phases (up to ~420%).[2][3] The volume change and the number of stress-induced cracks during different phase transitions can be different, given that these intermediate sodium-containing tin phases have different crystal structures and mechanical properties.[4] To prolong the lifetime of tin foil electrodes, it is crucial to determine which phase transitions have a greater impact on crack formation in the tin electrode and deliberately mitigate the problematic phase transitions.In this work, the mechanisms and kinetics of the phase transitions that occur in the sodiation of tin foil are extensively investigated using operando light microscopy and robust electrochemical techniques. Ex situ X-ray diffraction (XRD) (Figure 1) reveals that the initial sodiation of tin foil begins with a significant crystalline to amorphous transition (i.e., c-Sn to a-NaSn), followed by the a-NaSn to c-Na9Sn4 and the c-Na9Sn4 to c-Na15Sn4 transitions. To further understand these transitions, we introduce a new battery configuration for light microscopy to observe the dynamic change of the cross-section macrostructure of tin foil electrodes during cycling. It is expected that the observation could partly quantify the volume expansion during different phase transitions, directly visualize the formation of cracks, and accurately estimate the sodium diffusion coefficient in tin foil electrodes. Moreover, the change of charge transfer resistance as a function of sodiation depth is measured using electrochemical impedance spectroscopy (EIS), shedding light on the degradation mechanism. Besides, potentiostatic intermittent titration technique (PITT) is also employed to determine the role of diffusion or interfacial charge transfer on the whole kinetics of tin anode at different depths of discharge. These investigations could yield fundamental insights into the sodiation mechanisms and kinetics of tin foil electrodes, and more importantly, provide guidance for the utilization of binder- and additive-free tin foil as a reliable SIB anode. Figure 1

Advanced Characterization of Pillared Graphene-Based Materials for Supercapacitors

Materials for supercapacitors have to display large surface area to maximize the number of adsorbed ions [1], and they must also possess a hierarchical porosity (Fig. 1) to favour ions diffusion. Graphene-derived materials are studied as they –theoretically- combine all these porosity-related parameters. However experimentally the achieved capacitance (CSP) remains limited because graphene sheets tend to re-aggregate. Our group has selected a method to avoid this issue by creating an expanded graphene structure by bridging and separating the sheets using aliphatic diamine pillars. These assemblies are called Pillared Graphene materials (PGM). Electrochemical results showed that these PGM display higher capacitance than reference non pillared materials [2,3]. However, it was not possible to correlate these storage performances improvements to adsorption active surface area determined with N2 gas sorption (BET), which questions the suitability of this technique for measuring the full porosity of the samples, which is likely to be more accessible in an electrolytic environment. Therefore, to further correlate storage performances of PGM to their structure, structural advanced characterization techniques such as small angle X-ray and neutron scattering (SAXS/SANS) were employed.These methods enable to assess samples porosity at the local scale (~30 to 140nm) as well as the solid phase density. In the frame of this presentation, SAXS/SANS not only have been applied to pristine materials, but also to specifically formulated samples (pellet, electrodes) in order to highlight structural differences arising from synthesis protocol or from molecular pillaring. The ionic charge diffusion and adsorption in specific porosity ranges, analyzed using preliminary Operando scattering techniques, will be evoked. So far the interplay between increased adsorption sites and improved electrochemical performances has only been intuited on the basis of indirect electrochemical studies; the strategy devised herein proposes the use of direct structural techniques to confirm these interpretations.

Decoupled Electrolysis: A Novel Method for Water Splitting Using WO3 Auxiliary Electrode

More emphasis must be placed on the use of clean and renewable energy sources. Production of electricity using solar, wind geothermal etc is becoming more widespread however these types of energy production suffer from intermittence in production and a mismatch of production and consumption cycles. These problems result in a need for an energy storage medium. A hydrogen is a viable option because of its high gravimetric heat capacity (143 MJ/kg) and low flashpoint (-231°C) [1]. For now, most of the produced hydrogen is from hydrocarbons and only 4% is being produced using electrolysis. Hydrogen production via electrolysis is an efficient way how to store surplus energy from renewable energy sources but electrolysis must be made more achievable. Commonly used water electrolysis is limited by the need for complicated gas distribution systems to avoid mixing of H2 and O2 which can lead to a serious safety hazard. Membranes and diaphragms can solve gas mixing problems but they significantly reduce efficiency and increase hydrogen production costs.Here we demonstrate the principle of decoupled electrolysis where oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is separated in space with the use of a WO3 redox mediator. WO3 was produced by the solvothermal method. In accordance with SEM (Fei, NanoSEM 650), XRD (Rigaku, Ultima+) and XPS (Thermo Scientific, Escalab Xi+) data, monoclinic WO3 nanosheet assemblies with a cluster size of 10-20 μm and plate thickness of 50-100 nm were produced without lower oxidation states. Electrodes were produced using carbon felt which was saturated with ink suspension containing active material (WO3), carbon black and polyvinyl difluoride (PVDF) in a mass ratio of 60-30-10. DMF was used as a solvent. Electrolysis was achieved in a two-step process. In the first step, an OER reaction occurs and the H ion is intercalated into WO3 forming tungsten bronze HxWO3. OER reaction occurs on platinum and O2 is released with gas purity above 99.9 %. In the second step, H ion deintercalation occurs and H2 is released at the Pt electrode with a purity greater than 99.9%. Gas purity was determined using a gas mass spectrometer. Electrochemical measurements were performed using Metohm AutoLAB potentiostat with Nova software. The electrode was analysed using cyclic voltammetry (CVP), impedance spectroscopy (EIS) and chronopotentiometry. 0.5 M H2SO4 was used as an electrolyte solution.In accordance with the CVP capacity of the WO3 electrode reaches 325 F/g at a scan rate of 2 mV/s and decreases with an increase in scan speed. A decrease in capacity due to an increase in scanning speed can be associated with limited charge diffusion [2]. The shift of the maximum in the anodic direction associated with the transition from W5+ to W6+ with an increase in scan speed is polynomial and can be associated with the pseudocapacitive behaviour of electrode material. The Nyquist plot from EIS measurements shows the formation of an incomplete arc in the high-frequency interval and linear correlation in lower frequencies. In chronopotentiometry with a current density of 100 mA/g faradaic efficiency reached 90.2% and increased to 100% when 1000 mA/g were used, however taking into account both OER and HER reactions, cycle efficiency decreased from 65 to 43 % with the same current densities. If only HER reaction is analysed when hydrogen is being released and deintercalation happens, cycle efficiency reaches 341 %. High efficiency can be explained by extra energy obtained from the building potential of the WO3 electrode that lowers the standard potential for water electrolysis. Long-term tests showed good stability and no degradation was observed in accordance with SEM and XPS studies. At high intercalation-deintercalation cycle times, a non-Faradaic process can be observed which reduced HER cycle time. A spontaneous deintercalation can be observed. One of the future goals is to prevent this process by the use of different auxiliary electrode materials.[1]-Tashie-Lewis BC, Nnabuife SG. Hydrogen production, distribution, storage and power conversion in a hydrogen economy - a technology review. Chemical Engineering Journal Advances 2021;8:100172.[2]- Das AK, Karan SK, Khatua BB. High energy density ternary composite electrode material based on polyaniline (PANI), molybdenum trioxide (MoO3) and graphene nanoplatelets (GNP) prepared by sonochemical method and their synergistic contributions in superior supercapacitive performance. Electrochim Acta 2015;180:1e15. Figure 1

Investigation of the electrochemical behavior of a newly designed TiMg dental implant

This study is aimed to evaluate the galvanic corrosion of a newly designed TiMg dental implant. The TiMg composite was tested in two forms: (1) cylinders (TiMg cyl) and (2) dental implants (TiMg DI). Surface roughness was measured using a confocal microscope. The electrochemical behavior was determined in a Hank’s balanced salt solution (HBSS) by the open-circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) measurements. Surfaces after corrosion were examined by a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). OCP of TiMg cyl and TiMg DI increased in the noble direction, indicating the formation and growth of a base film on their surfaces. After 2-h immersion, TiMg cyl had higher values of iCorr and RCorr compared with those of TiMg DI. After 24-h immersion, a prominent reduction in the values of iCorr and RCorr was observed, and ECorr shifted positively. The Nyquist plots of TiMg cyl and TiMg DI show capacitive loops that tended to close after 2-h exposure. As the time extended, TiMg DI showed higher corrosion resistance compared with that of TiMg cyl, and the linear diffusion response arose from the formation and dissolution of chemically non-stable by-products caused by the hydrogen evolution. In such a case, the involved reaction was controlled by charge transfer and diffusion processes. The formation of a film composed of stable CAp species that attached directly to the surface and chemically non-stable by-products that included (Mg3(PO4)2) and Mg(OH)2 was demonstrated. To conclude, the obtained results revealed that TiMg DI of a complicated threaded design had a more stable passive film and higher corrosion resistance in HBSS compared with those of TiMg cyl of a cylindrical design. These findings have the utmost importance for the fabrication of dental implants.Graphical abstract

Enhancing Photocatalytic Properties of TiO2 Photocatalyst and Heterojunctions: A Comprehensive Review of the Impact of Biphasic Systems in Aerogels and Xerogels Synthesis, Methods, and Mechanisms for Environmental Applications.

This review provides a detailed exploration of titanium dioxide (TiO2) photocatalysts, emphasizing structural phases, heterophase junctions, and their impact on efficiency. Key points include diverse synthesis methods, with a focus on the sol-gel route and variants like low-temperature hydrothermal synthesis (LTHT). The review delves into the influence of acid-base donors on gelation, dissects crucial drying techniques for TiO2 aerogel or xerogel catalysts, and meticulously examines mechanisms underlying photocatalytic activity. It highlights the role of physicochemical properties in charge diffusion, carrier recombination, and the impact of scavengers in photo-oxidation/reduction. Additionally, TiO2 doping techniques and heterostructures and their potential for enhancing efficiency are briefly discussed, all within the context of environmental applications.

The potential of electrodialysis as a cost-effective alternative to reverse osmosis for brackish water desalination

While electrodialysis (ED) demonstrates lower energy consumption than reverse osmosis (RO) in the desalination of low salinity waters, RO continues to be the predominant technology for brackish water desalination. In this study, we probe this skewed market share and project the potential for future disruption by ED through systematic assessment of the levelized cost of water (LCOW). Using rigorous process- and economic-models, we minimize the LCOW of RO and ED systems, highlighting important tradeoffs between capital and operating expenditure for each technology. With optimized current state-of-the-art systems, we find that ED is more economical than RO for feed salinities ≤ 3 g L−1, albeit to a minor extent. Considering that RO is a highly mature technology, we focus on predicting the future potential of ED by evaluating plausible avenues for capital and operating cost reduction. Specifically, we find that reduction in the price of ion-exchange membranes (i.e., < 60 USD m−2) can ensure competitiveness with RO for feed salinities up to 5 g L−1. For higher feed salinities (≥ 5 g L−1) we reveal that the LCOW of ED may effectively be reduced by decreasing ion-exchange membrane resistance, while preserving high current efficiency. Through extensive assessment of structure-property-performance relationships, we precisely identify target membrane charge densities and diffusion coefficients which optimize the LCOW of ED, thus providing novel guidance for future membrane material development. Overall, we emphasize that with a unified approach — whereby ion-exchange membrane price is reduced and performance is enhanced — ED can become the economically preferable technology compared to RO across the entire brackish water salinity range.

Van Der Waals Semiconductor Based Omnidirectional Bifacial Transparent Photovoltaic for Visual-Speech Photocommunication.

Omnidirectional photosensing is crucial in optoelectronic devices, enabling a wide field of view (wFoV) and leveraging potential applications for the Internet of Things in sensors, light fidelity, and photocommunication. The wFoV helps overcome the limitations of line-of-sight communication, and transparent photodetection becomes highly desirable as it enables the capture of optical information from various angles. Therefore, developing a photoelectric device with a 360° wFoV, ultra sensitivity to photons, power generation, and transparency is of utmost importance. This study utilizes a heterojunction of van der Waals SnS with Ga2 O3 to fabricate a transparent photovoltaic (TPV) device showing a 360° wFoV with bifacial onsite power production. SnS/Ga2 O3 heterojunction preparation consists of magnetron sputtering and is free from nanopatterning/nanostructuring to achieve the desired wFoV window device. The device exhibits a high average visible transmittance of 56%, generates identical power from bifacial illumination, and broadband fast photoresponse. Careful analysis of the device shows an ultra-sensitive photoinduced defect-modulated heterojunction and photocapacitance, revealed by the impedance spectroscopy, suggesting photon-flux driven charge diffusion. Leveraging the wFoV operation, the TPV embedded visual and speech photocommunication prototype demonstrated, aiming to help visually and auditory impaired individuals, promising an environmental-friendly sustainable future.