Valence Change Research Articles

Study of the stoichiometry effect on the structure and loss kinetics of photogenerated current carriers in Cu2-δBaSnS4 (0≤δ≤0.4) quaternary copper compounds

The solid-phase method was applied to synthesize Cu2-δ BaSnS4 (0≤δ ≤ 0.4) polycrystalline powders. The lattice parameters were refined. It was shown that the crystal structure parameters changed. For the first time, Raman spectra were experimentally obtained for copper-deficient samples. It was found that some difference in the position of major peaks is due to the Cu2-δBaSnS4 structure changing with increasing δ, as well as a partial valence change in tin or copper atoms. Using X-ray photoelectron spectroscopy, it was shown that when going from Cu2BaSnS4 to Cu1.6BaSnS4, there was no change in the valence state of copper, but the valence state of tin particularly changed. The lifetimes of the current carriers in the synthesized samples were significantly less than 10 ns.

Effect of Mo6+ induced valence changes of transition metal ions in Mn-rich layered cathode materials on electrochemical performance

Layered cathode materials for lithium-ion batteries have been extensively investigated; however, comparatively scant attention has been paid to Mn-rich layered cathode materials. Herein, LiNi0.5Mn0.5O2 cathode materials are doped to investigate the effect of doping elements on the electrochemical properties of Mn-rich layered cathodes. XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), and SQUID (superconducting quantum interference device) results reveal that Mo doping affects the electrochemical properties of the cathode materials by changing the valence state of transition metal ions. Due to the Mo6+ ions doping, a large proportion of Mn3+ ions present in LiNi0.5Mn0.5O2 were converted to Mn4+ ions, which alleviated the Jahn-Teller effect and reduced the elongated Mn-O octahedra, thus increasing the Li layer spacing and facilitating Li+ diffusion. Therefore, 1 % Mo-doped cathode exhibits a significantly improved Li-ion diffusion coefficient and superior rate performance with a specific discharge capacity of 103 mAh·g−1 at 5C. Meanwhile, the cathode materials significantly improve cycling performance due to the reduction in the amount of Mn3+. The current study provides guidelines for the modification of Mn-rich layered cathodes in the future.

Transition mechanism and thermokinetic analysis of Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics for nuclear waste forms based on in-situ synthesis

In this study, the novelly designed Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics were utilized as nuclear waste form to simultaneously immobilize simulated fission products Sr and actinide nuclides. The phase transition mechanism, thermokinetics and densification behavior of Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics based on in-situ synthesis were systemically analyzed by XRD, in-situ XPS, TG-DSC, SEM and density measurements. The results demonstrate that the formation of Ce0.5Sm0.5PO4 solid solution phase preceded that of Sr0.5Zr2(PO4)3 phase, of which there is a valence change of Ce from Ce4+ to Ce3+ before 1023 K. Additionally, as for the exothermic crystallization enthalpy, change of exothermic crystallization enthalpy and activation energy, the values of Sr0.5Zr2(PO4)3 and Ce0.5Sm0.5PO4 phases in composite ceramics are 286.17 – 515.61 mJ, 19.11 – 35.38 J/g, 702.45 kJ/mol and 145.21 – 232.44 mJ, 9.26 – 15.44 J/g, 450.04 kJ/mol, respectively. It is then indicated that the formation of Ce0.5Sm0.5PO4 phase is definitely more favorable than that of Sr0.5Zr2(PO4)3 phase. Simultaneously, the relative densities of Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics are more than 95 % when the sintering temperature exceeds 1273 K.

Understanding the Reversible Transition of Unipolar and Bipolar Resistive Switching Characteristics in Solution-Derived Nanocrystalline Au-Co3O4 Thin-Film Memristors.

Nanocrystalline Au-Co3O4 thin films were fabricated through a facile solution-processing method, and voltage-polarity-dependent resistive switching (RS) characteristics including variability of Set/Reset voltages, stability of cycling endurance, and carriers transport mechanism were studied in the Pt/Au-Co3O4/Pt memory devices. The switching voltages of the Set and Reset processes in the bipolar RS memristors exhibited lower variability as compared to the unipolar resistance switching devices. Moreover, the switching performance of cycle-to-cycle endurance in bipolar mode had a smaller fluctuation than those of unipolar switching behavior. Based on the current-voltage curve fitting analysis, it was found that Ohmic-conduction behaviors dominated the carriers transport of low-resistance state regardless of unipolar or bipolar switching behaviors. The carrier transport of high resistance state was governed following Poole-Frenkel emission and Schottky emission mechanisms in the unipolar and bipolar switching modes, respectively. The physical switching mechanism of Pt/Au-Co3O4/Pt memory devices was proposed using the model by means of growth and disruption of conducting filaments, involved in memory effects of thermochemical mechanism and valence change mechanism in the unipolar and bipolar RS, respectively. The proposed model following the finite element method revealed the roles of electrical field distribution and temperature gradient to further clarify the RS mechanism. Our results open a door for understanding and optimizing oxide-based thin-film resistance switching memory devices.

Porous CuO Microspheres as Long-Lifespan Cathode Materials for Aqueous Zinc-Ion Batteries.

Cathode materials with conversion mechanisms for aqueous zinc-ion batteries (AZIBs) have shown a great potential as next-generation energy storage materials due to their high discharge capacity and high energy density. However, improving their cycling stability has been the biggest challenge plaguing researchers. In this study, CuO microspheres were prepared using a simple hydrothermal reaction, and the morphology and crystallinity of the samples were modulated by controlling the hydrothermal reaction time. The as-synthesized materials were used as cathode materials for AZIBs. The electrochemical experiments showed that the CuO-4h sample, undergoing a hydrothermal reaction for 4 h, had the longest lifecycle and the best rate of capability. A discharge capacity of 131.7 mAh g-1 was still available after 700 cycles at a current density of 500 mA g-1. At a high current density of 1.5 A g-1, the maintained capacity of the cell is 85.4 mA h g-1. The structural evolutions and valence changes in the CuO-4h cathode material were carefully explored by using ex situ XRD and ex situ XPS. CuO was reduced to Cu2O and Cu after the initial discharge, and Cu was oxidized to Cu2O instead of CuO during subsequent charging processes. We believe that these findings could introduce a novel approach to exploring high-performance cathode materials for AZIBs.

Ultralow‐Temperature (≤ −80 °C) Proton Pseudocapacitor with High Power‐Energy Density Enabled by Tailored Proton‐Rich Electrolyte and Electrode

AbstractProton‐based energy storage systems provide a more sustainable alternative for large‐scale energy storage applications. However, conventional proton batteries/pseudocapacitors suffer from severe capacity loss because of reduced ionic conductivity and water‐to‐ice conversion at ultralow temperatures. Here, anti‐freezing proton‐rich electrolytes with ultralow freezing point (below −80 °C) and high conductivity (7.89 mS cm−1 at −80 °C) are developed, combined with open framework‐structured Prussian blue analogous (VHCF) electrodes with proton‐rich binding sites, to construct a promising proton pseudocapacitor at ultralow temperatures. Hydrogen bond‐induced solvated structures and physicochemical properties are clarified by comprehensive characterization techniques and computational simulations. Temperature‐dependent structure and valence changes for VHCF electrodes at low temperatures are revealed, where the multi‐electron transfer reaction is affected by temperature to limit the capacity output. The proton pseudocapacitor (VHCF//6 m H2SO4//MoO3‐x) achieves excellent electrochemical performance in the temperature range from −80 to 25 °C, and delivers a voltage window of 0 to 2.8 V and a high energy density of 74.9 Wh kg−1 at −80 °C. This proton‐rich electrolyte‐electrode design principle suggests an effective strategy enabling next‐generation energy technology under extreme conditions.

Deep learning-based simultaneous bioavailability assessment and speciation analysis of dissolved organic copper

Algal copper uptake (i.e., Cu bioavailability) in the euphotic zone plays a vital role in algal photosynthesis and respiration, affecting the primary productivity and the source and sink of atmospheric carbon. Algal Cu uptake is controlled by natural dissolved organic Cu (DOCu) speciation (i.e., complexed with the dissolved organic matter) that conventionally could be tested by model prediction or molecular-level characterizations in the lab, while DOCu uptake are hardly directly assessed. Thus, the new chemistry-biology insight into the mechanisms of the Cu uptake process in algae is urgent. The DOCu speciation transformation (organic DOCu to free Cu(II) ions), enzymatic reduction-induced valence change (reduction of free Cu(II) to Cu(I) ions), and algal Cu uptake at the algae-water interface are imitated. Herein, an intelligent system with DOCu colorimetric sensor is developed for real-time monitoring of newly generated Cu(I) ions. Deep learning with whole sample image-based characterization and powerful feature extraction capabilities facilitates colorimetric measurement. In this context, the Cu bioavailability with 7 kinds of organic ligands (e.g., amino acids, organic acids, carbohydrates) can be predicted by the mimetic intelligent biosensor within 15.0 min i.e., the DOCu uptake and speciation is successfully predicted and streamlined by the biomimetic approach.

Replacement of Tyrosines by Unnatural Amino Acid Aminophenylalanine Leads to Metal-Mediated Aniline Free Radical Formation in a Copper Amine Oxidase.

Copper amine oxidases (CAOs) catalyze the oxidative deamination of primary amines to aldehyde, ammonia, and hydrogen peroxide as products and are widely distributed in bacteria, plants, and eukaryotes. These enzymes initiate the single turnover, post-translational conversion of an active site tyrosine to the redox cofactor 2,4,5-trihydroxyphenylalanine quinone (TPQ), subsequently employing TPQ to catalyze steady-state amine oxidation. The mechanisms of TPQ biogenesis and steady-state amine oxidation have been studied extensively, with consensus mechanisms proposed for both reactions. One unresolved issue has been whether the Cu2+ center must undergo formal reduction to Cu1+ in the course of the reaction. Herein, we investigate the properties of the active site of a yeast (Hansenula polymorpha) amine oxidase (HPAO) that has undergone site-specific insertion of a para-aminophenylalanine (pAF) into the position of either the precursor tyrosine to TPQ (Y405) or the two strictly conserved neighboring tyrosines (Y305 and Y407). While our original intention was to interrogate cofactor biogenesis using a precursor unnatural amino acid (UAA) of altered redox potential and pKa, we instead observe an unanticipated reaction assigned to an intramolecular electron transfer from pAF to the active site copper ion. We establish the generality of the observed active site chemistry using exogenously added, aniline-containing substrates under conditions that prevent side chain amine oxidation. The results support previous proposals that the activation of the TPQ precursor occurs in the absence of a formal valence change at the active site copper site. The described reaction of pAFs with the active site redox Cu2+ center of HPAO provides a prototype for either the engineering of the enzymatic oxidation of exogenous anilines or the insertion of site-specific free radical probes within proteins.

Resolving the Relaxation of Volatile Valence Change Memory

AbstractMemristive devices based on the valence change mechanism are highly interesting candidates for data storage and hardware implementation of synapses in neuromorphic circuits. Although long‐term retention is often required for data storage applications, a slight resistance drift of the low resistive state (LRS) is observed even for stable devices. For other devices, the LRS has been observed to decay rapidly to the high resistive state (HRS). These types of devices are of interest for neuromorphic circuits where short‐term plasticity is required. In this work, the LRS relaxation of volatile, crystalline Pt/SrTiO3/Nb:SrTiO3: devices is investigated in detail, yielding time constants ranging from milliseconds to seconds. The decay is analyzed in terms of the Gibbs free energy gradient for the contribution of oxygen ion migration. A relaxation model based on drift‐diffusion dynamics is presented. The model may serve as a tool for developing guidelines and design rules for future volatile memristive technology based on Schottky barrier mediated electron transport.

Multi-layers hexagonal hole MXene trap constructed by carbon vacancy defect regulation strategy enables high energy density potassium-ions storage

Due to the slow reaction kinetics of potassium-ions with large size radius in layered materials, the energy density of aqueous potassium-ion hybrid supercapacitors (PIHCs) is severely limited. At the same time, the treatment of defects is a “double-edged sword” in energy storage materials, which requires targeted and precise regulation. In order to solve this problem, multi-layers hexagonal hole MXene trap was constructed by using the carbon vacancy defect regulation strategy, and high specific capacitance and energy density potassium-ion storage was realised in PIHCs. The structure-activity relationship at the atomic level was elucidated in combination with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole MXene trap. By density functional theory, the adsorption energy and kinetic analysis of multi-layers hexagonal hole MXene for potassium-ions were calculated, and the optimal position and quantity of potassium-ions were determined. By quantitative analysis of electron band structure and differential charge density, the internal mechanism of high conductivity and energy density of multi-layers hexagonal hole MXene PIHCs was revealed.

Kondo effects in variable-valence manganese-substituted thulium selenide

The MnXTm1‒XSe (0 ≤ Х ≤ 0.2) solid solutions have been first synthesized and their structural, magnetic, and transport properties have been studied in the temperature range of 80–1000 K and magnetic fields of up to 12 kOe. The surface morphology of the samples has been examined and the chemical analysis has been carried out. It is shown that the valence change with the increasing substitution concentration is accompanied by a change in the lattice parameter and a decrease in the magnetic moment of the samples. The Kondo temperatures caused by the manganese and thulium subsystem have been found in the low- and room-temperature regions. The temperature of localization of small-radius polarons has been determined. A drastic decrease in the relaxation time in the range of the manganese ion percolation through the lattice in the MnXTm1‒XSe system has been established. The change of the current carrier type upon variation in the temperature and substitution concentration was determined from the Seebeck coefficient. A high-temperature extremum of thermopower was revealed, which is explained within the framework of the Anderson model.

Cu-doped KTN crystal with controllable, reversible, and fast photochromic properties: A superior electro-optical material for improving beam deflection performance

Improving the deflection performance of a beam deflector is urgently required to acquire optical signals for space laser communication and change the attitude and position of space targets and spacecraft. In this work, a Cu-doped potassium tantalate niobate (Cu-KTN) single crystal with fast photochromic and increased beam deflection properties is synthesized using the top-seeded solution growth method. When a Cu-KTN single crystal is irradiated with 405 nm light or ultraviolet (UV) light, the color changes from pale green to reddish brown. After light irradiation, the color gradually returns to yellowish green. Decolorization is accelerated under irradiation with green light or long-wavelength light, and the color changes to pale green. The origin of reversible photochromism reveals the fast valence change of Cu ions. In addition, ion doping improves the beam deflection angle of the secondary electro-optical effect of Cu-KTN (4.3 mrad, 1000 V) crystal compared with pure KTN (3.2 mrad, 1000 V). This study successfully synthesizes Cu-KTN single crystals with photochromic uses and establishes a new route for beam deflectors with significant deflection angles.

Temperature and pressure dependencies of Sm valence in SmB[formula omitted] Kondo insulator probed by x-ray absorption spectroscopy

Pressure and temperature induced valence changes in the Kondo insulator SmB6 have been investigated using x-ray absorption spectroscopy (XAS) along several isobaric cooling runs and one isothermal compression. The average valence of Sm at various pressure and temperature conditions is extracted from high quality XAS data by peak fitting procedures. The temperature dependence of the Sm valence at ambient pressure shows changes of slope near the known characteristic temperatures of gap formation (120 K) and the in-gap state (50 K). At higher pressures the average valence also shows similar temperature dependent trends upon cooling but the slope changes are less pronounced. This behavior is discussed in relation to the possible existence of an underlying first order valence transition and its critical end point. At constant temperature (T=20 K), the Sm valence increases rapidly with pressure; however, it remains far below the expected integer value (3+) near the onset of the magnetic ordering and gap closure. In addition, the local structure of SmB6 at ambient conditions has been analyzed using extended x-ray absorption fine structure.

Enhanced capacitive deionization for Cr(VI) removal from electroplating wastewater: Efficacy, mechanisms, and high-voltage flow electrodes

In recent years, researchers have increasingly focused on flow electrode capacitive deionization (FCDI) for heavy metal removal. However, the practical application of FCDI has been limited because of its low removal efficiency at low voltages. To address this limitation, we investigated Cr(VI) removal using FCDI in high-voltage mode (≥1.23 V). We aimed to clarify the mechanism and capabilities of high-voltage FCDI, including the removal energy efficiency, ion valence changes, migration process, and practical applications. Our findings demonstrate that even at high voltages (≤1.6 V), FCDI maintains efficient Cr(VI) removal and charge efficiency. This success was attributed to the significant IR drop in the FCDI system. Additionally, Cr (VI) removal by high-voltage FCDI results from a synergistic effect combining electroporation and electroreduction. The higher the applied voltage, the stronger was the electroporation capacity and the reduction ratio. Under the voltage condition of 2.2 V, the maximum electroporation capacity reached 172.82 mg g−1. However, excessively high-voltage can also lead to a more pronounced side reaction, resulting in a slow improvement in the removal efficiency. We further optimized the process parameters of the FCDI using response surface methodology (RSM). The optimized conditions yielded impressive results, a 99.96 % removal efficiency and low energy consumption (0.104 kWh/m3) in actual Cr(VI)-containing wastewater. Additionally, even in the 19th cycle of continuous operation, Cr(VI) removal by FCDI exceeded 90 %. This study unveils the efficacy and mechanism of Cr(VI) removal by high-pressure FCDI, which is expected to advance industrial applications of FCDI for treating heavy metal-containing wastewater.

Disease-specific alterations in central fear network engagement during acquisition and extinction of conditioned interoceptive fear in inflammatory bowel disease.

Interoceptive fear, which is shaped by associative threat learning and memory processes, plays a central role in abnormal interoception and psychiatric comorbidity in conditions of the gut-brain axis. Although animal and human studies support that acute inflammation induces brain alterations in the central fear network, mechanistic knowledge in patients with chronic inflammatory conditions remains sparse. We implemented a translational fear conditioning paradigm to elucidate central fear network reactivity in patients with quiescent inflammatory bowel disease (IBD), compared to patients with irritable bowel syndrome (IBS) and healthy controls (HC). Using functional magnetic resonance imaging, conditioned differential neural responses within regions of the fear network were analyzed during acquisition and extinction learning. In contrast to HC and IBS, IBD patients demonstrated distinctly altered engagement of key regions of the central fear network, including amygdala and hippocampus, during differential interoceptive fear learning, with more pronounced responses to conditioned safety relative to pain-predictive cues. Aberrant hippocampal responses correlated with chronic stress exclusively in IBD. During extinction, differential engagement was observed in IBD compared to IBS patients within amygdala, ventral anterior insula, and thalamus. No group differences were found in changes of cue valence as a behavioral measure of fear acquisition and extinction. Together, the disease-specific alterations in neural responses during interoceptive fear conditioning in quiescent IBD suggest persisting effects of recurring intestinal inflammation on central fear network reactivity. Given the crucial role of interoceptive fear in abnormal interoception, these findings point towards inflammation-related brain alterations as one trajectory to bodily symptom chronicity and psychiatric comorbidity. Patients with inflammatory conditions of the gut-brain axis may benefit from tailored treatment approaches targeting maladaptive interoceptive fear.

Simultaneous removal of ammonia nitrogen and manganese by anoxic/oxic (A/O) process from electrolytic manganese residue leachate

Ammonia nitrogen and manganese contained in the leachate of electrolytic manganese residue are causing serious damage to the ecological environment. In this study, anaerobic/oxic (A/O) process as a biological method to achieve simultaneous removal of nitrogen and manganese produced during the actual production of manganese. Results indicated that after 137 d of operation, the system achieved 96.73 ± 1.25%, 98.42 ± 0.60%, 96.97 ± 0.19%, and 100% removal of Mn(II), NH4+-N, TN, and chemical oxygen demand (COD), respectively. Extracellular polymeric substances (EPS) secreted by microorganisms was converted to carbon source to promote denitrification. Scanning electron microscopy (SEM) showed that Mn(II) formed manganese crystals in the process of complete reflection with sludge, acting as electron donor to achieve simultaneous removal of nitrogen and manganese, and removal of Mn(II) was found by X-ray photoelectron spectroscopy (XPS) through redox and valence changes. 16S rRNA indicated that Proteobacteria, Deinococcus-Thermus, Bacteroidete, and Firmicutes were involved in the process of removal nitrogen and manganese. The presence of Limnobacter allowed a more stable accumulation of NO2−-N in reactor, thus achieving shortcut nitrification-denitrification, and Flavihumibacter promoted the secretion of EPS. Collectively, the study reveals that the interaction of autotrophic denitrifying bacteria (Chryseolinea), heterotrophic denitrifying bacteria (Fusibacter, Thauera), and manganese-oxidizing bacteria (Pseudaminobacter, Bacillus, Pedomicrobium, Aeromonasr) achieved simultaneously removal of nitrogen and manganese from the reactor shortcut nitrification-denitrification. This study provides a new insight for the treatment of electrolytic manganese residue leachate produced in the process of manganese production.

The effect of emotional changes in composite reviews on consumers' information adoption from a dual perspective

PurposeWith the appearance of additional review functionality on e-commerce platforms emotional changes in composite reviews have become more diverse. How consumers process the emotional changes in composite reviews is an important concern for companies. This study investigates the impact of explores how changes in the emotional valence and emotional intensity of composite reviews on consumers' information adoption.Design/methodology/approachBased on emotion as social information theory, this study constructs a double mediation model of how the change in emotional valence of composite reviews affects consumers' adoption intention and examines the moderating effect of the dynamic change of emotional intensity. One field and three online experiments were conducted to test the proposed hypotheses.FindingsConsumers were more likely to adopt positive–negative composite reviews than negative–positive composite reviews. Compared to negative–positive composite reviews, positive–negative composite reviews led to higher perceived empathy and lower motivational suspicion, which, in turn, led to higher information adoption. Moreover, dynamic changes in emotional intensity played a moderating role in this effect. Interestingly, the amount of attribute difference changed the differences in perceived empathy and motivated consumer suspicion generated by the composite review when considering the reviewer’s attribute difference description.Originality/valueThe findings have important theoretical contributions that deepen business and consumer understanding of the impact of composite reviews and have practical implications for improving the management of composite reviews by businesses.

Inflection class interactions and valency changes in Matlatzinca

Abstract In this paper, we explore how changes in the inflection class membership of verbs in Matlatzinca (Oto-Pamean, Oto-Manguean, Mexico) lead to changes in both their valency and meaning. In Matlatzinca, verbs often exhibit multiple class membership so that a given verb may be inflected as transitive in one class but as intransitive in another. For instance, the verb chun+ta, when inflected in different classes, can encompass diverse meanings: the action of ‘waking someone up’; the result state of ‘being awake’; and the spontaneous event of ‘waking up’. This linguistic phenomenon is intriguing from both a typological and a theoretical perspective as it challenges our understanding of lexical representation by prompting the question of whether these meanings represent distinct lexical entries or various construals of the same verb (Spencer 2013).

Improved Na+ adsorption performance and storage mechanism of cobalt hexacyanoferrate/polyaniline composite during the hybrid capacitive deionization process

In order to realize high desalting capacity of capacitive deionization (CDI) system, cobalt hexacyanoferrate/polyaniline (CoHCF/PANI) composite with hollow hierarchical tubular structure was finely prepared by employing conductive hollow PANI tube as the interconnection skeleton for CoHCF cubic particles grown in situ, thereby endowing this composite with good conductivity, abundant redox active sites and stable structure. The synergistic effect between the CoHCF layer and PANI layer makes the CoHCF/PANI electrode possess superior specific capacitance (263.8F·g−1) and high contribution of the capacitance behavior (87.8 %) at 5 mV·s−1. Compared with either the single PANI or CoHCF electrode, the CoHCF/PANI electrode exhibits outstanding salt adsorption capacity (30.48 mg·g−1), rapid salt adsorption rate (3.66 mg·g−1·min−1) and excellent cycle stability (retention rate 98.1 %). Different from the CoHCF/PANI(+)‖AC(−) cell, there is no inversion peak in the AC(+)‖CoHCF/PANI(−) cell, which testifies that the CoHCF/PANI electrode is easier to capture Na+ ions. Based on the XPS spectra before and after desalination tests, the Na+ adsorption mechanism of the CoHCF/PANI electrode as cathode for the hybrid capacitive deionization (HCDI) system was further explored. It is found that the change of element valence in CoHCF/PANI composites (reduction of Fe3+ to Fe2+ and Co3+ to Co2+ in CoHCF, partial reduction of −C = N+ to −N–H- in PANI) is the main factor leading to Na+ intercalation. This study emphasizes the significance for fine design of the electrode material and strategic configuration of the HCDI cell.

WITHDRAWN: Multi-layers hexagonal hole MXene trap constructed by carbon vacancy defect regulation strategy enables high energy density potassium-ions storage

Due to the slow reaction kinetics of potassium-ions with large size radius in layered materials, the energy density of aqueous potassium-ion hybrid supercapacitors (PIHCs) is severely limited. At the same time, the treatment of defects is a "double-edged sword" in energy storage materials, which requires targeted and precise regulation. In order to solve this problem, multi-layers hexagonal hole MXene trap was constructed by using the carbon vacancy defect regulation strategy, and high specific capacitance and energy density potassium-ion storage was realized in PIHCs. The structure-activity relationship at the atomic level was elucidated in combination with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole MXene trap. By density functional theory, the adsorption energy and kinetic analysis of multi-layers hexagonal hole MXene for potassium-ions were calculated, and the optimal position and quantity of potassium-ions were determined. By quantitative analysis of electron band structure and differential charge density, the internal mechanism of high conductivity and energy density of multi-layers hexagonal hole MXene PIHCs was revealed.