Comorbid anxiety and depressive symptoms and the related factors among international medical students in China during COVID-19 pandemic: a cross-sectional study.

BACKGROUND: The two most prevalent mental health conditions are anxiety and depression and they often coexist (comorbidity) in an individual aggravating the person's psychological or medical conditions. College students suffered from anxiety and depressive symptoms during the COVID-19 pandemic, according to numerous studies. The lack of information on the comorbidity of anxiety and depression (CAD) among international medical students, however, makes it difficult to develop effective policies or strategies to support these students. OBJECTIVE: The present research seeks to investigate the incidence of CAD among international medical students in China and to identify the variables that may be useful in predicting CAD. METHOD: A cross-sectional study was conducted at China Medical University in Shenyang, China, for international medical students during November 2020. A total of 519 international students provided information on their demographics, stress related to the COVID-19 pandemic, generalized anxiety disorder assessment (GAD-7), patient health questionnaire-9 (PHQ-9), simplified coping style questionnaire (SCSQ), perceived stress scale (PSS-10), the multidimensional scale of perceived social support (MSPSS), revised life orientation test (LOT-R), and resilience scale-14 (RS-14). To investigate the potential predictors of CAD, a chi-square test, a nonparametric test, and multinomial logistic regression analyses were carried out as appropriate. RESULTS: The incidence of anxiety, depression, and CAD in the current study was 5.8%, 8.9%, and 22.7%, respectively. The predictors for students having symptoms of anxiety were observed to be the negative coping style (ß = 0.662, OR = 1.938, CI:1.07-3.694) and perceived stress (ß = 0.167, OR = 1.181, CI:1.076-1.297); the predictors for students having symptoms of depression were observed to be the COVID-19 pandemic-related stress (ß = 0.323,OR = 1.382,CI:1.211-1.577), negative coping style (ß = 0.693,OR = 2.000, CI:1.21-3.568), and perceived stress (ß = 0.135,OR = 1.145,CI:1.050-1.248); whereas the predictors for students with CAD were observed to be staying up late (Yes VS No) (ß = 1.028,OR = 2.794,CI:1.227-6.364), current place of residence (Other continents VS China) (ß = -1.413, OR = 0.243,CI:0.065-0.910), COVID-19 pandemic-related stress (ß = 0.371,OR = 1.450,CI:1.284-1.636), negative coping style (ß = 1.092,OR = 2.979,CI:1.706-5.203), and perceived stress (ß = 0.339,OR = 1.403,CI:1.289-1.527). CONCLUSION: Single anxiety and depressive symptoms were moderately prevalent among international medical students in China. However, CAD turned out to be the most prevalent mental health issue due to its relatively higher incidence. Negative coping style and perceived stress were the communal predictors of the three categories, whereas stress related to the COVID-19 pandemic was linked to both depression and CAD, and staying up late and in residential places were specific predictors for CAD. Study results suggest that COVID-19 pandemic-related stress was related to students' CAD and depressive symptoms, and specific intervention measures with stress reduction, proper coping strategy, and a good lifestyle might be useful in improving the international students' mental health status.

Stressors in university life and anxiety symptoms among international students: a sequential mediation model.

BACKGROUND: Anxiety is a common mental health problem among university students, and identification of its risk or associated factors and revelation of the underlying mechanism will be useful for making proper intervention strategies. The aim of our study is to test the sequential mediation of self-efficacy and perceived stress in the association between stressors in university life and anxiety symptoms. METHODS: A cross-sectional study design was adopted and a sample of 512 international students from a medical university of China completed the survey with measurements of stressors in university life, self-efficacy, perceived stress and anxiety symptoms. RESULTS: We found that 28.71% of the international students had anxiety symptoms, and stressors in university life were positively associated with anxiety symptoms (ß = 0.23, t = 5.83, p < 0.01). Moreover, sequential mediating role of self-efficacy and perceived stress in the association between the stressors and anxiety symptoms was revealed. CONCLUSIONS: Our study provided a new perspective on how to maintain the mental health, which suggested that self-efficacy improvement and stress reduction strategies should be incorporated in the training programs to support students.

Association of Covid-19 pandemic-related stress and depressive symptoms among international medical students.

BACKGROUND: The outbreak of Covid-19 had negative impacts on the mental stress and induced psychological distress among university students worldwide. This study proposed a moderated mediation model, and hypothesized that the Covid-19 pandemic-related stress was positively related to depressive symptoms among international medical students. METHODS: An online survey on stress and depressive symptoms of international students was conducted in a medical university. Questions on Covid-19 pandemic-related stress, Patient Health Quesionnaire-9, Simplified Coping Style Questionnaire and the Perceived Social Support Scale were used as measurements, and model analyses were conducted using Hayes' PROCESS macro for SPSS. RESULTS: It was found that 9.83%, 3.08% and 2.12% students had mild, moderate and severe depressive symptoms, respectively, and the positive association between Covid-19 pandemic-related stress and depressive symptoms was significant (ß = 0.27, t = 6.87, P < 0.01). Negative coping was also significantly correlated to depressive symptoms (ß = 0.26, t = 6.60, P < 0.01), and partially mediated the association between Covid-19 pandemic-related stress and depressive symptoms. Perceived social support had a negative association with depressive symptoms (ß=-0.26, t=-6.25, P < 0.01), played a negative moderating role in the relationship between negative coping and depressive symptoms, and moderated the indirect effect of Covid-19 pandemic-related stress on depressive symptoms via negative coping. CONCLUSIONS: Results of the study suggested that under the background of continuing pandemic, intervention or prevention of mental health problem is urgently needed for the international students, and depression may be alleviated through reducing negative coping and increasing perceived social support.

Bath Electrospinning of Continuous and Scalable Multifunctional MXene-Infiltrated Nanoyarns.

Electroactive yarns that are stretchable are desired for many electronic textile applications, including energy storage, soft robotics, and sensing. However, using current methods to produce these yarns, achieving high loadings of electroactive materials and simultaneously demonstrating stretchability is a critical challenge. Here, a one-step bath electrospinning technique is developed to effectively capture Ti3 C2 Tx MXene flakes throughout continuous nylon and polyurethane (PU) nanofiber yarns (nanoyarns). With up to ≈90 wt% MXene loading, the resulting MXene/nylon nanoyarns demonstrate high electrical conductivity (up to 1195 S cm-1 ). By varying the flake size and MXene concentration, nanoyarns achieve stretchability of up to 43% (MXene/nylon) and 263% (MXene/PU). MXene/nylon nanoyarn electrodes offer high specific capacitance in saturated LiClO4 electrolyte (440 F cm-3 at 5 mV s-1 ), with a wide voltage window of 1.25 V and high rate capability (72% between 5 and 500 mV s-1 ). As strain sensors, MXene/PU yarns demonstrate a wide sensing range (60% under cyclic stretching), high sensitivity (gauge factor of ≈17 in the range of 20-50% strain), and low drift. Utilizing the stretchability of polymer nanofibers and the electrical and electrochemical properties of MXene, MXene-based nanoyarns demonstrate potential in a wide range of applications, including stretchable electronics and body movement monitoring.

An Ultrafast Conducting Polymer@MXene Positive Electrode with High Volumetric Capacitance for Advanced Asymmetric Supercapacitors.

Pseudocapacitors or redox capacitors that synergize the merits of batteries and double-layer capacitors are among the most promising candidates for high-energy and high-power energy storage applications. 2D transition metal carbides (MXenes), an emerging family of pseudocapacitive materials with ultrahigh rate capability and volumetric capacitance, have attracted much interest in recent years. However, MXenes have only been used as negative electrodes as they are easily oxidized at positive (anodic) potential. To construct a high-performance MXene-based asymmetric device, a positive electrode with a compatible performance is highly desired. Herein, an ultrafast polyaniline@MXene cathode prepared by casting a homogenous polyaniline layer onto a 3D porous Ti3 C2 Tx MXene is reported, which enables the stable operation of MXene at positive potentials because of the enlarged work function after compositing with polyaniline, according to the first-principle calculations. The resulting flexible polyaniline@MXene positive electrode demonstrates a high volumetric capacitance of 1632 F cm-3 and an ultrahigh rate capability with 827 F cm-3 at 5000 mV s-1 , surpassing all reported positive electrodes. An asymmetric device is further fabricated with MXene as the anode and polyaniline@MXene as the cathode, which delivers a high energy density of 50.6 Wh L-1 and an ultrahigh power density of 127 kW L-1 .

Selective Charging Behavior in an Ionic Mixture Electrolyte-Supercapacitor System for Higher Energy and Power.

Ion-ion interactions in supercapacitor (SC) electrolytes are considered to have significant influence over the charging process and therefore the overall performance of the SC system. Current strategies used to weaken ionic interactions can enhance the power of SCs, but consequently, the energy density will decrease due to the increased distance between adjacent electrolyte ions at the electrode surface. Herein, we report on the simultaneous enhancement of the power and energy densities of a SC using an ionic mixture electrolyte with different types of ionic interactions. Two types of cations with stronger ionic interactions can be packed in a denser arrangement in mesopores to increase the capacitance, whereas only cations with weaker ionic interactions are allowed to enter micropores without sacrificing the power density. This unique selective charging behavior in different confined porous structure was investigated by solid-state nuclear magnetic resonance experiments and further confirmed theoretically by both density functional theory and molecular dynamics simulations. Our results offer a distinct insight into pairing ionic mixture electrolytes with materials with confined porous characteristics and further propose that it is possible to control the charging process resulting in comprehensive enhancements in SC performance.

Protective effect of walnut active peptide against dextran sulfate sodium-induced colitis in mice based on untargeted metabolomics.

Inflammatory bowel disease (IBD) is a chronic condition characterized by inflammation of the digestive tract, whose exact cause remains unknown, and its prevalence is on the rise. This study investigated the effects of a walnut-derived peptide LPLLR (LP-5) on intestinal inflammation and metabolism in IBD mice. Metabolomics revealed that LP-5 regulated the levels of metabolites, such as thalsimidine, fumagillin, and geniposide, and LP-5 could regulate several signaling pathways, such as protein digestion and absorption, aminoacyl-tRNA biosynthesis, and ABC transporters. Additionally, LP-5 alleviated dextran sulfate sodium (DSS)-induced colitis by modulating autophagy and inflammasome pathways. Western blotting demonstrated that LP-5 reduced the expressions of NLRP3, Caspase-1, ASC and IL-1ß, and increased the expressions of Beclin-1 and LC3-II/LC3-I, corresponding to activation of the AMPK/mTOR/ULK1 pathway. These findings suggested that LP-5 activated autophagy in vivo to suppress inflammation and modulate metabolic substances, highlighting potential implications for gut health and the development of functional foods containing LP-5.

Conjugated Polyelectrolyte Thin Films for Pseudocapacitive Applications.

A subclass of organic semiconductors known as conjugated polyelectrolytes (CPEs) is characterized by a conjugated backbone with ionic pendant groups. The water solubility of CPEs typically hinders applications of thin films in aqueous media. Herein, it is reported that films of an anionic CPE, namely CPE-K, drop cast from water produces single-component solid-state pseudocapacitive electrodes that are insoluble in aqueous electrolyte. That X-ray diffraction experiments reveal a more structurally ordered film, relative to the as-obtained powder from chemical synthesis, and dynamic light scattering measurements show an increase in aggregate particle size with increasing [KCl] indicate that CPE-K films are insoluble because of tight interchain contacts and electrostatic screening by the electrolyte. CPE-K film electrodes can maintain 85% of their original capacitance (84 F g-1 ) at 500 A g-1 and exhibit excellent cycling stability, where a capacitance retention of 93% after 100 000 cycles at a current density of 35 A g-1 . These findings demonstrate that it is possible to use initially water soluble ionic-organic materials in aqueous electrolytes, by increasing the electrolyte concentration. This strategy can be applied to the application of conjugated polyelectrolytes in batteries, organic electrochemical transistors, and electrochemical sensors, where fast electron and ion transport are required.

Dual-modified starch micelles as nanocarriers for efficient encapsulation and controlled release of walnut-derived active peptides.

Hydrophilic and hydrophobic modified nanomicelles might be more conducive to passage of the gastrointestinal barrier than walnut peptide (WP). In this study, a novel double modified starch polymer, SB-CST-DCA, was synthesized by grafting sulfabetaine (SB) and deoxycholic acid (DCA) onto corn starch (CST) molecules through etherification and esterification. The modification mechanism was discussed to determine its chemical structure, morphological properties, and thermal stability. Peptide-loaded nanomicelles (SB-CST-DCA-WP) were prepared using WP as the core material. The encapsulation efficiency and peptide loading amount reached 76.90 ± 1.52% and 18.27 ± 0.53%, respectively, with good stability and pH-responsive release behavior observed to effectively control WP release and enhance its antioxidant activity. The composite exhibited safety, non-toxicity, and good blood compatibility at concentrations below 125 µg/mL. Duodenum was identified as the main absorption site with an absorption ratio of 41.16 ± 0.36%.

High-Performance Aqueous Supercapacitors Based on a Self-Doped n-Type Conducting Polymer.

Environmentally-benign materials play a pivotal role in advancing the scalability of energy storage devices. In particular, conjugated polymers constitute a potentially greener alternative to inorganic- and carbon-based materials. One challenge to wider implementation is the scarcity of n-doped conducting polymers to achieve full cells with high-rate performance. Herein, this work demonstrates the use of a self-doped n-doped conjugated polymer, namely poly(benzodifurandione) (PBDF), for fabricating aqueous supercapacitors. PBDF demonstrates a specific capacitance of 202 ± 3 F g-1, retaining 81% of the initial performance over 5000 cycles at 10 A g-1 in 2 m NaCl( aq ). PBDF demonstrates rate performances of up to 100 and 50 A g-1 at 1 and 2 mg cm-2, respectively. Electrochemical impedance analysis reveals a surface-mediated charge storage mechanism. Improvements can be achieved by adding reduced graphene oxide (rGO), thereby obtaining a specific capacitance of 288 ± 8 F g-1 and high-rate operation (270 A g-1). The performance of PBDF is examined in symmetric and asymmetric membrane-less cells, demonstrating high-rate performance, while retaining 83% of the initial capacitance after 100 000 cycles at 10 A g-1. PBDF thus offers new prospects for energy storage applications, showcasing both desirable performance and stability without the need for additives or binders and relying on environmentally friendly solutions.

Acidic "Water-in-Salt" Electrolyte Enables a High-Energy Symmetric Supercapacitor Based on Titanium Carbide MXene.

Titanium carbide MXene, Ti3C2Tx, exhibits ultrahigh capacitance in acidic electrolytes at negative potentials yet poor stability at positive potentials, resulting in low-energy densities for Ti3C2Tx-based symmetric supercapacitors. Utilizing "water-in-salt" electrolytes has successfully expanded the stable operation potential window of MXenes. However, this advancement comes at the cost of sacrificing their high capacitance in acidic electrolytes. In this work, we report an acidic "water-in-salt" (AWIS) electrolyte composed of sulfuric acid and saturated lithium halide, which effectively doubled the energy density of the Ti3C2Tx-based symmetric supercapacitor compared to those with bare acidic electrolytes. Specifically, the AWIS electrolyte successfully expanded the voltage window of the symmetric device to 1.1 V. A high specific capacitance of 112.34 F g-1 (at 10 mV s-1) was obtained due to the presence of proton redox. As a result, the symmetric device achieved a high-energy density of 19.1 Wh kg-1 and a high capacitance retention of 96.3% after 10,000 cycles. This work demonstrates the importance of designing stable and redox-active electrolytes for high-energy MXene-based symmetric supercapacitors.

Structure Design and Processing Strategies of MXene-Based Materials for Electromagnetic Interference Shielding.

The development of new materials for electromagnetic interference (EMI) shielding is an important area of research, as it allows for the creation of more effective and high-efficient shielding solutions. In this sense, MXenes, a class of 2D transition metal carbides and nitrides have exhibited promising performances as EMI shielding materials. Electric conductivity, low density, and flexibility are some of the properties given by MXene materials, which make them very attractive in the field. Different processing techniques have been employed to produce MXene-based materials with EMI shielding properties. This review summarizes processes and the role of key parameters like the content of fillers and thickness in the desired EMI shielding performance. It also discusses the determination of power coefficients in defining the EMI shielding mechanism and the concept of green shielding materials, as well as their influence on the real application of a produced material. The review concludes with a summary of current challenges and prospects in the production of MXene materials as EMI shields.

Walnut-Derived Peptide Improves Cognitive Impairment in Colitis Mice Induced by Dextran Sodium Sulfate via the Microbiota-Gut-Brain Axis (MGBA).

In this study, we investigated the protective mechanism of walnut-derived peptide LPLLR (LP-5) against cognitive impairment induced in a dextran sodium sulfate (DSS)-induced colitis mouse model, with emphasis on the microbiota-gut-brain axis (MGBA). The results revealed that LP-5 could improve the learning ability and memory of mice with cognitive impairment and mitigate colitis symptoms, including weight loss, bloody stools, colon shortening, and histopathological changes. Additionally, LP-5 protected the integrity of the intestinal barrier by promoting the expression of tight junction proteins (TJs) while attenuating colonic inflammation by suppressing proinflammatory cytokine and epithelial cell apoptosis. Western blotting indicated that LP-5 treatment suppressed the inflammatory NF-κB/MLCK/MLC signaling pathway activity. Furthermore, LP-5 ameliorated hippocampal neuron damage and protected blood-brain barrier (BBB) integrity by downregulating microglia marker protein Iba-1, increasing TJ protein expression, and restoring the deterioration of synaptic proteins. Importantly, 16S rRNA sequencing results indicated that LP-5 reshaped the abundance of a wide range of gut microbiota at the phylum and genus levels, with increased Prevotella and Akkermansia associated with tryptophan (TRP), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA). These findings suggest that LP-5 could maintain intestinal barrier and BBB integrity, reverse gut dysbiosis, and improve learning and memory ability in colitis mice, providing novel insights into alterations of gut microbes in colitis and a potential new mechanism by which it causes cognitive impairment.

Interfacial Designs of MXenes for Mild Aqueous Zinc-Ion Storage.

Limited Li resources, high cost, and safety risks of using organic electrolytes have stimulated a strong motivation to develop non-Li aqueous batteries. Aqueous Zn-ion storage (ZIS) devices offer low-cost and high-safety solutions. However, their practical applications are at the moment restricted by their short cycle life arising mainly from irreversible electrochemical side reactions and processes at the interfaces. This review sums up the capability of using 2D MXenes to increase the reversibility at the interface, assist the charge transfer process, and thereby improve the performance of ZIS. First, they discuss the ZIS mechanism and irreversibility of typical electrode materials in mild aqueous electrolytes. Then, applications of MXenes in different ZIS components are highlighted, including as electrodes for Zn2+ intercalation, protective layers of Zn anode, hosts for Zn deposition, substrates, and separators. Finally, perspectives are put forward on further optimizing MXenes to improve the ZIS performance.

Recyclable Conjugated Polyelectrolyte Hydrogels for Pseudocapacitor Fabrication.

In alignment with widespread interest in carbon neutralization and sustainable practices, we disclose that conjugated polyelectrolyte (CPE) hydrogels are a type of recyclable, electrochemically stable, and environmentally friendly pseudocapacitive material for energy storage applications. By leveraging ionic-electronic coupling in a relatively fluid medium, one finds that hydrogels prepared using a fresh batch of an anionic CPE, namely, Pris-CPE-K, exhibit a specific capacitance of 32.6 ± 6.6 F g-1 in 2 M NaCl and are capable of 80% (26.1 ± 6.5 F g-1) capacitance retention after 100,000 galvanostatic charge-discharge (GCD) cycles at a current density (J) of 10 A g-1. We note that equilibration under a constant potential prior to GCD analysis leads to the K+ counterions in the CPE exchanging with Na+ and, thus, the relevant active material Pris-CPE-Na. It is possible to remove the CPE material from the electrochemical cell via extraction with water and to carry out a simple purification through dialysis to produce a recycled material, namely Re-CPE-Na. The recycling workup has no significant detrimental impact on the electrochemical performance. Specifically, Re-CPE-Na hydrogels display an initial specific capacitance of 26.3 ± 1.2 F g-1 (at 10 A g-1) and retain 77% of the capacitance after a subsequent 100,000 GCD cycles. Characterization by NMR, FTIR, and Raman spectroscopies, together with XPS and GPC measurements, revealed no change in the structure of the backbone or side chains. However, rheological measurements gave evidence of a slight loss in G' and G''. Overall, that CPE hydrogels display recyclability argues in favor of considering them as a novel materials platform for energy storage applications within an economically viable circular recycling strategy.

Relationships Between Cross-Cultural Adaption, Perceived Stress and Psychological Health Among International Undergraduate Students From a Medical University During the COVID-19 Pandemic: A Moderated Mediation Model.

International university students may be at greater risk for developing psychological problems due to the unique stressors in them, particularly during the COVID-19 pandemic. The purpose of present study is to propose and test a moderated mediation model that would illuminate the underlying relationships of cross-cultural adaption, perceived stress and psychological health as well as the moderating effect of optimism and resilience among international medical undergraduates in China during the COVID-19 pandemic. The study was conducted via a web-based survey in November 2020. Electronic informed consents were obtained from all participants. A total of 453 students including 233 males and 220 females aged 18 to 28 years with an average age of 22.09 (SD = 2.73) completed the questionnaires. Symptom Checklist 90, the measurement of cross-cultural adaption, the Perceived Stress Scale, the Life Orientation Test-Revised and the Resilience Scale were used for the survey. Results for the moderated mediation model testing revealed that cross-cultural adaption significantly and negatively associated with the Global Severity Index (GSI) of the Symptom Checklist 90 (ß = -0.24, P < 0.01), and perceived stress partially mediated the relationship. Optimism (ß = -0.29, P < 0.01) and confidence in COVID-19 control (ß = -0.19, P < 0.01) had direct negative effects on perceived stress. Furthermore, optimism and resilience negatively moderated the indirect effect of cross-cultural adaption on psychological health through perceived stress. Findings of this study suggest that university educators ought to promote or make use of programs that cope with stress and boost optimism and resilience in order to support students not only adapt well to a new culture, but also keep good psychological health during the period of COVID-19 pandemic.

Prevalence and Predictors of Anxiety and Depressive Symptoms Among International Medical Students in China During COVID-19 Pandemic.

Background: The rapid spread of Coronavirus Disease-19 (COVID-19) infection has been the most important public health crisis across the globe since the end of 2019. Anxiety and depression are the most common mental health problems among people during the pandemic, and many studies have reported anxiety and depressive symptoms in college students. However, information on the mental health status of international medical students during this critical period of time has been scarce, which hinders the efforts in making proper policy or strategies to help these students. The present study aims to explore the prevalence of anxiety and depressive symptoms in international medical students in China and to find out the factors that have potential predictive value for anxiety and depressive symptoms. Method: A cross-sectional study was carried out for international medical students during November 2020 at China Medical University in Shenyang, China. Five hundred and nineteen international students were interviewed with questionnaires containing demographic variables, Stressors in school, Generalized Anxiety Disorder Assessment (GAD-7), Patient Health Questionnaire-9 (PHQ-9), Simplified Coping Style Questionnaire (SCSQ), Perceived Stress Scale (PSS-10), the Multidimensional Scale of Perceived Social Support (MSPSS), Revised Life Orientation Test (LOT-R) and Resilience Scale-14 (RS-14). Univariate logistic regression and stepwise multiple logistic regression analyses were conducted where appropriate to explore the predictive factors of anxiety symptoms and depressive symptoms. Results: The prevalence of anxiety symptoms and depressive symptoms in the sample population was 28.5% (148/519) and 31.6% (164/519), respectively. Stressors in school (ß = 0.176, OR = 1.192, CI: 1.102-1.289), negative coping style (ß = 0.639, OR = 1.894, CI: 1.287-2.788) and perceived stress (ß = 0.230, OR = 1.258, CI: 1.184-1.337) were found to be the predictors of anxiety symptoms among the international medical students; while gender (ß = -0.594, OR = 0.552, CI: 0.315-0.968), stay up late (ß = 0.828, OR = 2.288, CI: 1.182-4.431), current place of residence (ß = 1.082, OR = 2.951, CI: 1.256-6.931), stressors in the school (ß = 0.303, OR = 1.354, CI: 1.266-1.496), negative coping style (ß = 0.866, OR = 2.377, CI: 1.516-3.725), perceived stress (ß = 0.233, OR = 1.262, CI: 1.180-1.351) were found to be predictors of depressive symptoms. Conclusion: The prevalence of anxiety symptoms and depressive symptoms was moderate among international medical students in China. The communal predictors of anxiety and depressive symptoms were stressors in school, negative coping style and perceived stress; while demographic factors such as gender (male), stay up late at night and current place of residence were found associated with depressive symptoms. These results suggest that proper stress management and specific interventions are needed to help students maintain their mental health during the COVID-19 pandemic period.

Titanium Carbide MXene Shows an Electrochemical Anomaly in Water-in-Salt Electrolytes.

Identifying and understanding charge storage mechanisms is important for advancing energy storage. Well-separated peaks in cyclic voltammograms (CVs) are considered key indicators of diffusion-controlled electrochemical processes with distinct Faradaic charge transfer. Herein, we report on an electrochemical system with separated CV peaks, accompanied by surface-controlled partial charge transfer, in 2D Ti3C2Tx MXene in water-in-salt electrolytes. The process involves the insertion/desertion of desolvation-free cations, leading to an abrupt change of the interlayer spacing between MXene sheets. This unusual behavior increases charge storage at positive potentials, thereby increasing the amount of energy stored. This also demonstrates opportunities for the development of high-rate aqueous energy storage devices and electrochemical actuators using safe and inexpensive aqueous electrolytes.

Ion Structure Transition Enhances Charging Dynamics in Subnanometer Pores.

Using electrodes with subnanometer pores and ionic liquid electrolytes can improve the charge storage capacity at the expense of the charging rate. The fundamental understanding of the charging dynamics of nanoporous electrodes can help to avoid compromising the power density. In this work, we performed molecular dynamics simulations to reveal the charging mechanism of subnanometer pores in ionic liquids. Different from the traditional view that a smaller pore results in slower charging, a non-monotonic relation is found between the charging rate and pore size, in which the charging process is accelerated in some subnanometer pores. Our analysis uncovers that the mechanism of the charging enhancement can be attributed to the transition of in-pore ion structure.

Maximizing ion accessibility in MXene-knotted carbon nanotube composite electrodes for high-rate electrochemical energy storage.

Improving the accessibility of ions in the electrodes of electrochemical energy storage devices is vital for charge storage and rate performance. In particular, the kinetics of ion transport in organic electrolytes is slow, especially at low operating temperatures. Herein, we report a new type of MXene-carbon nanotube (CNT) composite electrode that maximizes ion accessibility resulting in exceptional rate performance at low temperatures. The improved ion transport at low temperatures is made possible by breaking the conventional horizontal alignment of the two-dimensional layers of the MXene Ti3C2 by using specially designed knotted CNTs. The large, knot-like structures in the knotted CNTs prevent the usual restacking of the Ti3C2 flakes and create fast ion transport pathways. The MXene-knotted CNT composite electrodes achieve high capacitance (up to 130 F g-1 (276 F cm-3)) in organic electrolytes with high capacitance retention over a wide scan rate range of 10 mV s-1 to 10 V s-1. This study is also the first report utilizing MXene-based supercapacitors at low temperatures (down to -60 °C).