Depletion Region Research Articles

Manufacture, characterization, and elucidation of drug release mechanisms of etonogestrel implants based on ethylene vinyl acetate

In this work, etonogestrel implants were manufactured using coextrusion. The purpose of the study was to correlate changes in microstructure and transport properties that occurred in etonogestrel implants to drug release mechanisms. The implants consisted of an EVA 28 (28 % vinyl acetate) core containing dispersed and dissolved etonogestrel, and an EVA 15 (15 % vinyl acetate) skin. The drug release was determined to be via diffusion at a controlled rate and governed by implant dimensions. In-vitro release revealed evidence of supersaturation in the implant core and skin, likely from the intense mechanical energy input during the twin-screw manufacturing process. Subsequently during storage under ambient conditions, supersaturation resulted in recrystallization of drug crystals, preferentially in the implant core. Etonogestrel solubility and diffusivity in EVA were determined by permeation experiments and used for release modeling. Drug release from the EVA skin layer deviated from the predicted values due to 1) formation of a drug depletion zone in the core and 2) presence of a stagnant media layer adjacent to the skin. Drug release from implant ends was significantly faster than predicted. Air-filled pores were observed in the implant core using microCT which likely contributed to the faster release from implant ends.

Comprehensive characterization of nitrogen-related defect states in β-Ga2O3 using quantitative optical and thermal defect spectroscopy methods

This study provides a comprehensive analysis of the dominant deep acceptor level in nitrogen-doped beta-phase gallium oxide (β-Ga2O3), elucidating and reconciling the hole emission features observed in deep-level optical spectroscopy (DLOS). The unique behavior of this defect, coupled with its small optical cross section, complicates trap concentration analysis using DLOS, which is essential for defect characterization in β-Ga2O3. A complex feature arises in DLOS results due to simultaneous electron emission to the conduction band and hole emission to the valence band from the same defect state, indicating the formation of two distinct atomic configurations and suggesting metastable defect characteristics. This study discusses the implications of this behavior on DLOS analysis and employs advanced spectroscopy techniques such as double-beam DLOS and optical isothermal measurements to address these complications. The double-beam DLOS method reveals a distinct hole emission process at EV+1.3 eV previously obscured in conventional DLOS. Optical isothermal measurements further characterize this energy level, appearing only in N-doped β-Ga2O3. This enables an estimate of the β-Ga2O3 hole effective mass by analyzing temperature-dependent carrier emission rates. This work highlights the impact of partial trap-filling behavior on DLOS analysis and identifies the presence of hole trapping and emission in β-Ga2O3. Although N-doping is ideal for creating semi-insulating material through the efficient compensation of free electrons, this study also reveals a significant hole emission and migration process within the weak electric fields of the Schottky diode depletion region.

Synthesis of Sn-ZnO nanostructures on MgO by hybrid pulsed laser ablation and RF magnetron sputtering tandem system for CO gas-sensing application

An exceptional method of incorporating Sn ions into Zinc Oxide (ZnO) using a tandem system of Pulsed Laser Deposition (PLD) and Radio-Frequency Magnetron Sputtering (RFMS) to synthesize and functionalize ZnO nanostructures is demonstrated in this study for gas-sensing application. The RFMS power was varied up to 50 W to sputter a pure Sn metal target, while simultaneously or successively growing ZnO nanostructures on a templated MgO < 0001 > substrate and on an Au-plated Al2O3 gas sensor, via PLD process at the substrate temperature of 700 °C in 100–500 millitorr oxygen/argon gas background. The morphologies of the grown Sn-ZnO nanostructures were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray Diffraction (XRD), and while their chemical/oxidation states and optical properties were analyzed by X-ray photospectroscopy (XPS) and photoluminescence (PL), respectively. For simultaneous deposition, the resulting (0002)-dominated 2D grain-like ZnO nanostructures were influenced by the interaction of the dynamic PLD plasma with static RFMS plasma at different powers. For successive growth, at 50 W-RF power, a remarkable increase in the sensor response to 50-ppm carbon monoxide (CO) gas was observed at 250 °C, which could be attributed to the creation of more adsorption sites in the Sn-ZnO depletion region caused by the replacement of some Zn sites with Sn ions in the ZnO matrix. This study, therefore, exhibits the viability of this hybrid system to design, synthesize, and functionalize Sn-ZnO nanomaterials, either by simultaneous/successive deposition, for gas-sensing applications.

Insight into photocatalytic chlortetracycline degradation by WO3/AgI S-scheme heterojunction: DFT calculation, degradation pathway and electron transfer mechanism

The construction of S-scheme heterojunction with excellent redox ability holds promising prospects for photocatalytic environment remediation. However, the rationally design of the heterojunction interface to achieve efficient charge transfer still faces challenges. In this study, we fabricated a tight-contacted S-scheme heterojunction by in situ anchoring AgI nanoparticles onto WO3 nanoplates. The significant difference in Fermi energy levels between WO3 and AgI results in the formation of a space charge region around the interface and bending of the energy band, facilitating directional migration and spatial separation of charge carriers. This contributes to enhanced generation of superoxide radicals (•O2−) and holes (h+) active species, leading to a significant increase in chlortetracycline (CTC) degradation rate. The apparent rate constant for CTC removal using the WO3/AgI (WA-2) is approximately 15 times higher than that observed for pure WO3. Furthermore, WA-2 exhibits universal degradation effects on tetracycline (TC) and oxytetracycline (OTC). Molecular dynamics (MD) simulation reveals the synergistic adsorption effect of WO3 and AgI on CTC and reactive oxygen species molecules. Based on Fukui function calculation of CTC molecules and degradation intermediates, liquid chromatography-mass spectrometry (LC-MS) analysis, photocatalytic degradation pathway over WO3/AgI was determined to be sequential demethylation followed by dechlorination and decarbonylation. These findings provide valuable insights into high-performance S-scheme heterojunctions interface design and elucidation of pollutant degradation mechanism.

Impacts of quantum confinement effect on threshold voltage and drain-induced barrier lowering effect of junctionless surrounding-gate nanosheet NMOSFET including source/drain depletion regions

In order to modeling of junctionless (JL) surrounding-gate (SG) nanosheet MOSFET more accurately, a new model for determining threshold voltage and drain-induced barrier lowering (DIBL) effect of JL SG nanosheet NMOSFET is proposed through deriving the Poisson's equation under rectangular coordinate system. The model captures quantum confinement effect and source/drain depletion regions, it is validated through the Sentaurus TCAD simulation results. Variations of source/drain depletion regions with the channel width, height, doping concentration, the gate bias, the drain bias and variations of threshold voltage, DIBL with the channel width, height, doping concentration considering and not considering quantum confinement effect are studied, respectively. The results show influences of quantum confinement effect on source/drain depletion regions, threshold voltage and DIBL. The developed model will offer quantum corrections in JL SG nanosheet NMOSFET.

Theoretical investigation of 4d noble metal (Ru, Rh or Pd) single atom structures influencing surface oxygen behavior on SnO2(1 1 0)

Surface oxygen species play a key role in determining the chemi-resistive gas sensing performance of SnO2. Through surface modification, the type of oxygen species at different working temperatures can be modulated, leading to changes in carrier concentration and surface activity. Single atom structures (SAS) hold enormous potential in the gas sensing domain; however, the impact of different SAS on surface oxygen species on SnO2 remains unclear, resulting in inconsistent improvements in sensing properties. This study conducted a theoretical investigation of different 4d noble metal SAS (Ru, Rh, and Pd) modified SnO2(110) surface, encompassing both electronic and chemical sensitization. All three SAS, when substituting penta-coordinated Sn atom (Sn5c), can inject holes and create a thicker depletion layer to varying degrees. Ru and Rh SAS can accelerate the decomposition of adsorbed O2 and O3. More importantly, Ru and Rh can hinder the combination of adsorbed O* species with adjacent two-coordinated lattice oxygen (O2c), enhancing the chemical stability of O*, which plays a decisive role in detecting reducing gases, with Ru exhibiting a better effect. This theoretical work not only enhances methods and mechanisms for adjusting surface oxygen species and improving the sensing performance of SnO2-based gas sensors, but also provides useful guidance for screening and designing SAS in experimental procedures on different semiconductor metal oxide surfaces.

High-performance solar-blind photodetector of β-Ga2O3 grown on sapphire with embedding an ultra-thin AlN buffer layer

The authors reported the MOCVD growth of high-quality β-Ga2O3 on c-plane sapphire substrate, resulting in the achievement of high performance solar blind deep UV photodetectors by introducing an ultra-thin AlN buffer seed layer (BSL). Compared with the direct growth of Ga2O3 on the sapphire, the oxygen vacancy of β-Ga2O3 is reduced after introducing an AlN BSL and the full width at half maximum (FWHM) of (-201) diffraction peak becomes narrower. The dark current is reduced by 1000 times and from 10−10 A down to 10−13 A for the metal-semiconductor-metal planner photodetector of β-Ga2O3 thin film with the AlN BSL. And the detectivity reaches 4.65×1015 cm·Hz1/2·W at 5 V bias. This improvement in performance is derived from the improvement of the growth quality of β-Ga2O3 mediated by the AlN BSL due to the decrease of lattice mismatch. The defects in β-Ga2O3 are reduced, the carrier concentration is reduced, the Fermi level is shifted, the depletion region is widened, the probability of electron tunneling in the dark state is reduced, and the dark current is effectively reduced.

A novel photoelectrochemical based water splitting and uric acid biosensing using PLD grown In2Se3 thin films

By altering the deposition pressure during the film growth process using the pulsed laser deposition (PLD) technology, indium selenide (In2Se3) thin films have been optimized to produce their distinct phases. The phase purity, optical and morphological studies were carried out using XRD, Raman spectroscopy, XPS, UV–visible spectroscopy, AFM and FESEM measurements. A high absorption in the visible region is observed for In2Se3 thin films with suitable band edges for hydrogen evolution. Photoelectrochemical (PEC) activity for In2Se3 photoelectrodes having various phases was analyzed based on CV and I-t response. A good charge transport characteristics were observed using the EIS measurements on PLD grown In2Se3 thin films. The Mott–Schottky analysis for the charge carrier density, flat band potential, and depletion layer width was performed for the deposition pressure dependent phase formation and high performance for PEC water splitting conversion efficiency of 0.48 %, 0.57 % and 0.98 % corresponding to α-In2Se3, β-In2Se3 and γ-In2Se3 were observed, respectively. The as prepared In2Se3 thin films were employed for the detection of Uric Acid (UA) using the cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. The high sensitivity (0.38 mA/mM), selectivity and repeatability of the prepared biosensor demonstrates In2Se3 as potential candidate for the PEC based water splitting and biosensing application without the presence of an external mediator and can work in the self-powered mode.

Frequency-dependent capacitance and conductance characteristics and current transport mechanisms of Schottky diodes with TPA-IFA organic interfacial layer

In this study, a Schottky barrier diode with an Al/TPA-IFA/p-Si structure was fabricated using spin coating and thermal evaporation methods. Using forward and reverse bias I–V measurement, we examined the key electrical characteristics of the Al/TPA-IFA/p-Si diode, including Φb, n, Rs, and Nss; we also estimated VD, NA, EF, ∆Φb, WD, Φb and Nss using C–V measurements under the different frequencies (10, 50, 100, 500 kHz, and 1 MHz) at room temperature. Using I–V data and the Thermionic Emission (TE) theory, basic electrical parameters such as ideality factor ( n ), and barrier height ( Φb ) values were computed as 3.01 and 0.716 eV. The fundamental diode parameters are highly frequency-dependent. It was also found that the series Resistance ( Rs ) values reduced with increasing frequency, but the barrier height ( Φb ) and the width of the depletion layer ( WD ) increased. It was found that when frequency increased, the diode capacitance reduced for our new Schottky-type diode. The diode’s potential conduction mechanisms were examined through the utilization of reverse lnI−V0.5 and forward lnI−V graphs. The transport properties of Al/TPA-IFA/p-Si diode are primarily governed by ohmic conduction, Space Charge Limited Current (SCLC), and Trap Charge Limited Current (TCLC) mechanisms at low, moderate, and high voltages, respectively. It was concluded that the Poole–Frenkel Emission (PFE) mechanism was dominant for the Al/TPA-IFA/p-Si diode. Ultimately, the findings confirmed that the TPA-IFA-based diode could be obtained for the electronic application.

16.48% Efficient solution-processed CIGS solar cells with crystal growth and defects engineering enabled by Ag doping strategy

Solution-processed Cu(In,Ga)Se2 (CIGS) solar cells suffer from serious carrier recombination and power conversion efficiency (PCE) loss because of the poor film properties and easy formation of defects. Herein, we propose Ag&Se co-selenization strategy to enhance the crystallization and passivate harmful defects of the CIGS films. The formation of Ag-Se phase during the selenization process enables the formation of large grains and suppresses the deep level defects. It is found that Ag doping can enlarge the depletion region width, lower the Urbach energy and prolong the carrier lifetime. As a result, a champion solution-processed CIGS solar cell presents a high efficiency of 16.48% with the highly improved open-circuit voltage (VOC) of 662 mV and fill factor (FF) of 75.8%. This work provides an efficient strategy to prepare high quality solution-processed CIGS films for high-performance CIGS solar cells.

Surface reconstruction of defect-engineered MIL-88@Fe2O3 p-n heterojunction for enhanced electrocatalytic water and urea oxidation

Defective p-n heterojunction engineering has been under the spotlighted as a promising strategy for electrochemical oxygen evolution reaction (OER) and urea oxidation reaction (UOR). Still, it remains a great challenge how to use the space-charge region of p-n heterojunction to study the regulation mechanism of the p-n heterogeneous interface and vacancy defects on the incomplete self-reconstruction from pristine materials to (oxy)hydroxides. Herein, NH2-MIL-88b(Fe)/α-Fe2O3 p-n heterojunction with rich oxygen vacancies (denoted as p-n MIL-88@Fe2O3-OV) has been prepared using a simple one-step solvothermal method. The prepared catalyst exhibits promising electrocatalytic performance for OER and UOR, requiring low potentials of 1.50 and 1.35 V to reach the current density of 10 mA cm−2, respectively. The combined in-situ/ex-situ experimental and theoretical investigations unveil that p-n heterojunction engineering can not only facilitate charge transfer from n-type α-Fe2O3 to p-type NH2-MIL-88b(Fe) (denoted as MIL-88) and generate abundant oxygen vacancies, but also appreciably trigger phase transformation of MIL-88 into active FeOOH. The reconstructed FeOOH/α-Fe2O3 heterojunction optimizes the bonding strength towards key oxygen-containing intermediates and boosts the intrinsic activity. This work provides new insight into the self-reconstruction effect in the p-n heterojunction for enhancing the OER and UOR catalytic activity.

Characterization of interface states and investigation of possible current conduction mechanisms in the Pt, Au, Cu/n-InP Schottky diodes

Based on the capacitance/conductance–voltage (C/G–V) and current–voltage (I–V) methods, the interface characteristics and the current conduction mechanisms of Pt/n-InP Schottky contacts were studied in detail. The interface states strongly affected the values of capacitance in the depletion region. From Terman, G–V, and forward I–V methods, the interface state density (D it) was found to range from mid-1012 to mid-1013 eV−1cm−2. The forward current characteristics was not elucidated by the thermionic emission (TE) model assisted by tunneling via the interfacial layer. Rather, the spatially distributed inhomogeneous barrier could interpret the forward current characteristics. Trap-assisted tunneling involving phosphorous vacancy (VP)-related defects was observed to be dominant in the case of the reverse current characteristics. The comparison of Pt metal contact with Cu and Au contacts revealed that Pt contact has the highest D it among three contacts.

Development of coupled fluid-flow/geomechanics model considering storage and transport mechanism in shale gas reservoirs with complex fracture morphology

Field observations frequently demonstrate stress fluctuations resulting from the reservoir depletion. The development of reservoirs, particularly the completion of infill wells and refracturing, can be significantly impacted by stress changes in and around drainage areas. Previous studies mainly focus on plane fractures and few studies consider the influence of complex transport and storage mechanism and irregular fracture geometry on stress evolution in shale gas reservoirs. Based on the embedded discrete fracture model (EDFM) and finite-volume method (FVM), a coupled geomechanics/fluid model has been successfully developed considering the adsorption, desorption, diffusion and slippage of shale gas. This model achieves coupling simulation of natural fractures, hydraulic fractures with complex geometry, storage and transport mechanism, reservoir stress, and pore-elastic effect. The open-source software OpenFOAM is used as the main solver for this model. The stress calculation and productivity simulation of the model are verified by the classical poroelasticity problem and the simulation results of published research and commercial simulator with EDFM respectively. The simulation results indicate that σxx, σyy, σxy and Δσ changes with time and space due to the time effect and anisotropy of formation pressure depletion; Due to the influence of different mechanisms on shale gas storage and transport, the reservoir pressure and stress distribution under different mechanisms are different; Among them, the stress with full mechanisms differs the most compared to the stress without any mechanism. The reservoir with stronger stress sensitivity (smaller Biot coefficient) is less sensitive to formation pressure depletion, and the stress variation range is smaller. For reservoirs with weak stress sensitivity, formation pressure depletion is more likely to lead to stress reversal. Under the influence of fracture geometry, the pressure depletion regions caused by the three types of fracture geometry are approximately rectangular, parallelogram and square, respectively. The corresponding σxx, σyy and Δσ also have great differences in spatial distribution and values. Therefore, the time effect, shale gas storage and transport mechanism and the influence of complex fracture geometry should be considered when predicting pressure depletion induced stress under the condition of simultaneous production. This study is of great significance for understanding the evolution law of stress induced by pressure consumption, as well as the design of infill wells and repeated fracturing.

Exploring the Bonding Nature of Iron(IV)-Oxo Species through Valence Bond Calculations and Electron Density Analysis.

Compound I (Cpd I) plays a pivotal role in substrate transformations within the catalytic cycle of cytochrome P450 enzymes (P450s). A key constituent of Cpd I is the iron(IV)-oxo unit, a structural motif also found in other heme enzymes and nonheme enzymes. In this study, we performed ab initio valence bond (VB) calculations, employing the valence bond self-consistent field (VBSCF) and breathing orbital valence bond (BOVB) methods, to unveil the bonding nature of this vital "Fe(IV)═O″ unit in bioinorganic chemistry. Comparisons were drawn with the triplet O2 molecule, which shares some electronic characteristics with iron(IV)-oxo. Additionally, Cpd I models of horseradish peroxidase (HRP) and catalase (CAT) were analyzed to assess the proximal ligand effect on the electronic structure of iron(IV)-oxo. Our VB analysis underscores the significant role of noncovalent resonance effects in shaping the iron(IV)-oxo bonding. The resonance stabilization within the π and σ frameworks occurs to comparable degrees, with additional stabilization resulting from resonance between VB structures from these frameworks. Furthermore, we elucidated the substantial influence of proximal and equatorial ligands in modulating the relative significance of different VB structures. Notably, in the presence of these ligands, iron(IV)-oxo is better described as iron(III)-oxyl or iron(II)-oxygen, displaying weak covalent character but enhanced by resonance effects. Although both species exhibit diradicaloid characters, resonance stabilization in iron(IV)-oxo is weaker than in O2. Further exploration using the Laplacian of electron density shows that, unlike O2, which exhibits a charge concentration region between its two oxygen atoms, iron(IV)-oxo species display a charge depletion region.

Excellent NO2 sensor based on porous Pd-ZnO nanorods prepared by a facile hydrothermal method

Noble metal nanoparticles (NPs) decorated on the surface of semiconducting metal oxides to enhance the gas-sensitive properties of sensing materials have attracted considerable interest from numerous researchers worldwide. Here, we introduce an effective method to decorate Pd NPs on the surface of porous ZnO nanorods to improve NO2 gas-sensing performance. Porous ZnO nanorods were synthesized using a simple hydrothermal method without surfactant. Surface decoration of porous ZnO nanorods with Pd NPs was performed through in situ reduction of PdCl2 using Pluronic as the reducing agent. The gas-sensing properties of porous Pd-ZnO nanorods were evaluated toward NO2 toxic gas in a concentration range of 0.1–2 ppm at various operating temperatures of 25 °C–250 °C. Pd NPs decorated on the surface of porous ZnO nanorods not only improve the sensor response (3-folds) and reproducibility but also reduce the optimal operating temperature. The improvement in gas-sensing activity is attributed to the modulation of the depletion layer via oxygen adsorption and the formation of the Schottky potential barrier between Pd and ZnO through chemical and electronic mechanisms.

A novel method to solve analytically the non-linear Poisson equation in the inversion layer of a MOSFET

Abstract Despite the enormous importance that the metal oxide semiconductors (MOS) and the field effect transistors (MOSFETs) have in the actual semiconductor technology, the task of finding the analytical solution of the Poisson equation in the inversion layer was not fully accomplished for more than half a century. It is a well-known fact that due to the non-linear nature of this equation, the attempts to solve it got stuck after the first integration. Nevertheless, experimental and applied researchers found ways to characterize, control, and develop MOSFET devices based on approximate models, and numerical calculations. Here I present a new method to analytically solve the nonlinear Poisson equation, in principle, for any charge distribution in the inversion layer of a MOS, and for the charge density of the original Shockley model, in particular. To this purpose, a physical argument related to the charge and field energies in the transient population-inversion process is introduced and a new nonlinear but solvable second order differential equation is obtained, whose solution also solves the original Poisson equation. The analytical results presented here allow us to derive explicit expressions for the electrical potential distribution and, very importantly, for the charge distribution, the inversion layer width and the effective impurity concentration in the depletion layer. The quantum Hall effect and other physical phenomena were discovered in the inversion layer of a MOS. The Hall effect was explained under the assumption that the charge distribution is a two-dimensional electron gas, we show here however that the 2D limit is reached only at high gate voltages. When applied to MOSFET structures, we obtain new expressions for the drain currents in the inversion and depletion layers, as functions of the impurity concentration and the gate voltage for single and double-gate MOSFETs, and we give an insight for multi-gate MOSFETs.

Phonon-assisted leakage current of InGaN light emitting diode

We report on the leakage current mechanism in a blue GaN-based light-emitting diode (LED). The device structure was grown by the MOCVD technique on a sapphire substrate. The LED was characterized through various measurements including current-voltage, electroluminescence, and secondary ion mass spectroscopy (SIMS). Capacitance-voltage measurements were employed to calculate the depletion layer thickness at different bias voltages and to analyze the doping profile in the active layer. The reverse temperature-dependent current-voltage measurements were carried out to study the leakage mechanism. The leakage current was explained by phonon-assisted tunneling of charge carriers through deep trap states. The trap energy and density of states were extracted from the application of the introduced model. Cathodoluminescence measurements were performed to evaluate the density of dislocations, which were then compared to x-ray diffraction measurements. The determined value was close to the density of states obtained from the tunneling model.

Spectral selectivity of luminescence of a copper ion-exchange layer in sodium-potassium-magnesium silicate glass

The bright luminescence of the copper ion-exchange layer in glass has potential applications as a converter of electric spark and corona discharge radiation in devices for the rapid analysis of metals because of its selectivity. The selectivity of the luminescence of the copper ion-exchange layer was achieved by the presence of different luminescent centers within it. In this work, the copper monomers, Cu+-Cu+ monovalent dimers, and Cun molecular clusters were formed in an ion-exchange layer of sodium-potassium-magnesium silicate glass (SiO2-Na2O-CaO-MgO-Al2O3-K2O-Fe2O3). The luminescence of the copper ion exchange layer was characterized by steady-state spectroscopy and time-resolved spectroscopy. Molecular copper clusters Cun exhibited luminescence in the nanosecond range, and Cu+ monomers and Cu+-Cu+ monovalent dimers in the microsecond range, respectively. At the same time the formation of divalent copper led to a limitation in the duration of ion exchange for the production of luminescent glasses. Heat treatment of the ion-exchange layers led to an increase in the concentration of molecular copper clusters, Cu+-Cu+ monovalent dimers, and Cu2+ divalent monomers.

Ultra-antiwetting Membrane for Hypersaline Water Crystallization in Membrane Distillation.

Membrane distillation (MD) has great potential in the management of hypersaline water for zero liquid discharge (ZLD) due to its high salinity tolerance. However, the membrane wetting issue significantly restricts its practical application. In this study, a composite membrane tailored for extreme concentrations and even crystallization of hypersaline water is synthesized by coating a commercial hydrophobic porous membrane with a composite film containing a dense polyamide layer, a cation exchange layer (CEL), and an anion exchange layer (AEL). When used in direct contact MD for treating a 100 g L-1 NaCl hypersaline solution, the membrane achieves supersaturation of feed solution and a salt crystal yield of 38.0%, with the permeate concentration at <5 mg L-1. The composite membrane also demonstrates ultrahigh antiwetting stability in 360 h of long-term operation. Moreover, ion diffusion analysis reveals that the ultrahigh wetting resistance of the composite membrane is attributed to the bipolar AEL and CEL that eliminate ion crossover. The literature review elucidates that the composite membrane is superior to state-of-the-art membranes. This study demonstrates the great potential of the composite membrane for direct crystallization of hypersaline water, offering a promising approach to filling the gap between reverse osmosis and conventional thermal desalination processes for ZLD application.

Understanding Activity and Stability of Ru1-XMxO2 Oxygen Evolution Reaction Catalyst Surfaces (M = Ti, Zr): Theory and Experiments

Proton-exchange membrane water electrolyzers, pivotal for sustainable hydrogen production, encounter challenges in the oxygen evolution reaction (OER) marked by high overpotential and limited electrocatalyst stability. This study delves into the computational exploration of two metal substitutions, titanium (Ti) and zirconium (Zr), within ruthenium oxide (RuO2), aiming to enhance catalytic stability. The investigation encompasses nanoscale titanium-substituted and zirconium-substituted rutile RuO2, (Ru1-xMxO2) and evaluating their atomic and electronic structures, OER activity, and dissolution behavior.In the case of Ti substitution, varying concentrations (x = 0–50 at %) were systematically investigated. Our experiments and theoretical analyses elucidate concentration-dependent effects on the electronic structure, showcasing shifts in the d-band and O2p band centers. Titanium substitution induces electron accumulation and depletion regions on the surface, influencing OER activity and stability. Electrochemical testing corroborates the theory, demonstrating that lower Ti concentrations (12.5 and 20 at %) enhance catalyst stability and mitigate ruthenium dissolution. Specifically, Ti substitution influences reaction pathways, with penta-coordinated Ru sites exhibiting the lowest barriers for OER, while hexa-coordinated Ru sites facilitate lower energetic barriers for dissolution.Simultaneously, the study extends to the substitution of Zr within rutile RuO2. Computational and experimental analyses reveal anisotropic shifts in the rutile unit cell, dependent on Zr concentration. Zr substitution induces alterations in the electronic structure, impacting the surface density of states and electron density distribution. Experimentally, lower OER activity is observed for Zr-substituted RuO2 compared to pure RuO2, consistent with computational averages across all sites. However, specific sites with Zr substitution exhibit higher theoretical OER activity. Dissolution analyses underscore the complexity of interactions, with Zr affecting activation barriers for Ru dissolution, thus influencing OER stability.Notably, the dissolution behavior emerges as a critical aspect of this investigation. In Ti-substituted RuO2, experimental accelerated durability testing showcases enhanced stability and reduced Ru dissolution at low and intermediate Ti concentrations. Computational analyses corroborate these findings, indicating site-specific effects on both OER activity and stability. Conversely, Zr-substituted RuO2 exhibits lower Ru dissolution compared to commercial RuO2, emphasizing the role of Zr in impeding Ru dissolution while contributing to surface restructuring.In conclusion, this comprehensive exploration of Ti and Zr substitutions within ruthenium oxide advances our understanding of their effects on atomic and electronic structures, OER activity, and dissolution dynamics. The intricate interplay between specific sites, metal concentrations, and substituents provides valuable insights for designing high-performance, cost-effective OER nanoscale electrocatalysts. The findings underscore the importance of considering both activity and stability in the pursuit of efficient and durable electrocatalysts for sustainable hydrogen production.