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88 result(s) for "Yang, Junhe"
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Effects of sacrificial reagents on photocatalytic hydrogen evolution over different photocatalysts
The effect of sacrificial reagents (SRs) on photocatalytic H 2 evolution rate over different photocatalysts was systematically studied. Zn 0.5 Cd 0.5 S, graphitic carbon nitride (g-C 3 N 4 ), and TiO 2 were chosen as typical photocatalysts, while alcohols, amines, carboxylic acids, and inorganic Na 2 S/Na 2 SO 3 were chosen as SRs. The results indicate that Na 2 S/Na 2 SO 3 , methanol, and triethanolamine are the most suitable SRs for Zn 0.5 Cd 0.5 S, TiO 2 , and g-C 3 N 4 , respectively. It was found that in selecting organic SRs, both the permittivity and oxidation potential have profound effects on the H 2 production efficiency, which will provide basis for choosing appropriate SRs for different photocatalysts.
Examining K-12 teachers’ feelings, experiences, and perspectives regarding online teaching during the early stage of the COVID-19 pandemic
This mixed-methods study explored K-12 teachers’ feelings, experiences, and perspectives regarding online teaching during the COVID-19 pandemic. The study also examined teachers’ perspectives of the “new normal” after COVID-19 and of what should be done to better prepare teachers for future emergencies. Both quantitative and qualitative data were collected from an online survey and follow-up interviews. A total of 107 teachers from 25 different states in the United States completed the online survey, and 13 teachers from 10 different states participated in the follow-up interviews. The results revealed teachers’ feelings about online teaching and various strategies and tools they used during the early stage of the COVID-19 pandemic. The major challenges faced by teachers during the pandemic included lack of student participation and engagement (or lack of parental support), students without access to technology, concerns about students’ well-being, no face-toface interactions with students, no work-life balance, and learning new technology. Four major themes emerged regarding how to better prepare teachers for future emergencies: (1) professional development for online learning, (2) technology access, (3) technology training for both teachers and students, and (4) action plans and communication. Regarding teachers’ perspectives of the “new normal,” five major themes emerged: (1) more online or blended learning, (2) rethinking normal, (3) hygiene and social distancing, (4) smaller classes and different school schedules, and (5) uncertainty and concerns about the “new normal.”
Homologous Strategy to Construct High-Performance Coupling Electrodes for Advanced Potassium-Ion Hybrid Capacitors
HighlightsA novel and facile homologous strategy is proposed to construct unique multichannel carbon fiber (MCCF)-based electrode materials for potassium-ion hybrid capacitors.The S-MCCF anodes present high capacity, super rate capability, and long cycle stability in potassium-ion half-cells, and the aMCCF cathodes have a high specific surface area of 1445 m2 g−1 and exhibit outstanding capacitive performance.The fabricated PIHC (manode:mcathode = 1:2) devices show high energy and power densities together with excellent cycling stability.Potassium-ion hybrid capacitors (PIHCs) have been considered as promising potentials in mid- to large-scale storage system applications owing to their high energy and power density. However, the process involving the intercalation of K+ into the carbonaceous anode is a sluggish reaction, while the adsorption of anions onto the cathode surface is relatively faster, resulting in an inability to exploit the advantage of high energy. To achieve a high-performance PIHC, it is critical to promote the K+ insertion/desertion in anodic materials and design suitable cathodic materials matching the anodes. In this study, we propose a facile “homologous strategy” to construct suitable anode and cathode for high-performance PIHCs, that is, unique multichannel carbon fiber (MCCF)-based anode and cathode materials are firstly prepared by electrospinning, and then followed by sulfur doping and KOH activation treatment, respectively. Owing to a multichannel structure with a large interlayer spacing for introducing S in the sulfur-doped multichannel carbon fiber (S-MCCF) composite, it presents high capacity, super rate capability, and long cycle stability as an anode in potassium-ion cells. The cathode composite of activated multichannel carbon fiber (aMCCF) has a considerably high specific surface area of 1445 m2 g−1 and exhibits outstanding capacitive performance. In particular, benefiting from advantages of the fabricated S-MCCF anode and aMCCF cathode by homologous strategy, PIHCs assembled with the unique MCCF-based anode and cathode show outstanding electrochemical performance, which can deliver high energy and power densities (100 Wh kg−1 at 200 W kg−1, and 58.3 Wh kg−1 at 10,000 W kg−1) and simultaneously exhibit superior cycling stability (90% capacity retention over 7000 cycles at 1.0 A g−1). The excellent electrochemical performance of the MCCF-based composites for PIHC electrodes combined with their simple construction renders such materials attractive for further in-depth investigations of alkali-ion battery and capacitor applications.
Uniform and Anisotropic Solid Electrolyte Membrane Enables Superior Solid‐State Li Metal Batteries
Rational structure design is a successful approach to develop high‐performance composite solid electrolytes (CSEs) for solid‐state Li metal batteries. Herein, a novel CSE membrane is proposed, that consists of interwoven garnet/polyethylene oxide‐Li bis(trifluoromethylsulphonyl)imide (LLZO/PEO‐LiTFSI) microfibers. This CSE exhibits high Li‐ion conductivity and exceptional Li dendrite suppression capability, which can be attributed to the uniform LLZO dispersion in PEO‐LiTFSI and the vertical/horizontal anisotropic Li‐ion conduction in the CSE. The uniform LLZO particles can generate large interaction regions between LLZO and PEO‐LiTFSI, which thus form continuous Li‐ion transfer pathways, retard the interfacial side reactions and strengthen the deformation resistance. More importantly, the anisotropic Li‐ion conduction, that is, Li‐ion transfers much faster along the microfibers than across the microfibers, can effectively homogenize the electric field distribution in the CSE during cycling, which thus prevents the excessive concentration of Li‐ion flux. Finally, solid‐state Li||LiFePO4 cells based on this CSE show excellent electrochemical performances. This work enriches the structure design strategy of high‐performance CSEs and may be helpful for further pushing the solid‐state Li metal batteries towards practical applications. A novel composite solid electrolyte that consists of interwoven inorganic/organic hybrid microfibers is proposed, which exhibit uniform inorganic filler dispersion and vertical/horizontal anisotropic Li‐ion conduction. These unique characteristics enable superior Li‐ion conduction properties, especially in terms of even Li plating due to the homogenization of the electric field distribution in the electrolyte.
Diurnal dynamics of different circadian transcription modules in Chinese pine needles and roots during dormancy induction
Winter dormancy ensures that trees in temperate zones respond appropriately to environmental variations, thereby enhancing their adaptability and resilience. In the northern hemisphere, the dormancy of conifers is induced by short-day and cold temperature. Previous studies have revealed that TFL2 is a key regulator involved in conifers’ bud set and growth cessation during the dormancy-induced phase. Based on the annual expression profile analysis of PtTFL2 in Chinese pine ( Pinus tabuliformis Carr.), we identified key time nodes for dormancy initiation in autumn. To provide insight of the diurnal transcriptome dynamic in needles and roots during dormancy introduction, RNA-seq was performed at 12 consecutive time points in 24 h under natural environment in P. tabuliformis . Interestingly, we found that both needles and roots have rhythmic oscillatory genes, even though the roots could not receive light signals directly. We applied weighted gene co-expression network analysis (WGCNA) to integrate differentially expressed genes between needles and roots at different time points into highly correlated gene modules. Although the two modules are subject to different transcriptional controls during dormancy, both contain 35 identical transcriptional regulators. Some transcriptional factors with functional similarities and synergistic effects were found to play a role in the regulatory pathway, which provided some data support for mining gene functions and analyzing related regulatory pathways. Our results provide new insights into the molecular regulatory mechanisms involved in pine dormancy.
Free-Standing Sodium Titanate Ultralong Nanotube Membrane with Oil-Water Separation, Self-Cleaning, and Photocatalysis Properties
In this work, a free-standing sodium titanate ultralong nanotube membrane for multifunctional water purification has been prepared. For obtaining this free-standing membrane with good tenacity, one-dimensional (1D) sodium titanate ultralong nanotubes with a diameter of about 48 nm and length of hundreds of micrometers were prepared from TiO2 nanoparticles by a stirring hydrothermal method, which can be easily assembled into 2D membranes by facile vacuum filtration. After modified with methyltrimethoxysilane (MTMS), the free-standing membrane with hydrophobic surface possesses oil-water separation, self-cleaning and photocatalytic functions at the same time, which is favorable for the recovery of membrane and decontamination of various pollutants including oils, dust, and organic dyes from water. Furthermore, this membrane also exhibits excellent alkaline, acid, and corrosive salt resistance. This free-standing sodium titanate membrane with multifunction has potential applications in efficient wastewater purification and environmental remediation.
Visible-Light Driven TiO2 Photocatalyst Coated with Graphene Quantum Dots of Tunable Nitrogen Doping
Nitrogen doped graphene quantum dots (NGQDs) were successfully prepared via a hydrothermal method using citric acid and urea as the carbon and nitrogen precursors, respectively. Due to different post-treatment processes, the obtained NGQDs with different surface modifications exhibited blue light emission, while their visible-light absorption was obviously different. To further understand the roles of nitrogen dopants and N-containing surface groups of NGQDs in the photocatalytic performance, their corresponding composites with TiO2 were utilized to degrade RhB solutions under visible-light irradiation. A series of characterization and photocatalytic performance tests were carried out, which demonstrated that NGQDs play a significant role in enhancing visible-light driven photocatalytic activity and the carrier separation process. The enhanced photocatalytic activity of the NGQDs/TiO2 composites can possibly be attributed to an enhanced visible light absorption ability, and an improved separation and transfer rate of photogenerated carriers.
Mitigating voltage decay of O3‐NaNi1/3Fe1/3Mn1/3O2 layered oxide cathode for sodium‐ion batteries by incorporation of 5d metal tantalum
The cycling stability of O3‐type NaNi1/3Fe1/3Mn1/3O2 (NFM) as a commercial cathode material for sodium ion batteries (SIBs) is still a challenge. In this study, the Ni/Fe/Mn elements are replaced successfully with tantalum (Ta) in the NFM lattice, which generated additional delocalized electrons and enhanced the binding ability between the transition metal and oxygen, resulting in suppressed lattice distortion during charging and discharging. This caused significant mitigation of voltage decay and improved cycle stability within the potential range of 2.0–4.2 V. The optimized Na(Ni1/3Fe1/3Mn1/3)0.97Ta0.03O2 sample achieved a reversible capacity of 162.6 mAh g−1 at a current rate of 0.1 C and 73.2 mAh g−1 at a high rate of 10 C. Additionally, the average charge/discharge potential retention reached 98% after 100 cycles, significantly mitigating the voltage decay. This work demonstrates a significant contribution towards the practical utilization of NFM cathodes in the SIBs energy storage field. This study addresses the challenge of cycling stability in O3‐NaNi1/3Fe1/3Mn1/3O2 cathode for SIBs by substituting Ni/Fe/Mn with 5d metal tantalum, leading to suppressed lattice distortion. The optimized Na(Ni1/3Fe1/3Mn1/3)0.97Ta0.03O2 sample demonstrates improved reversible capacity, rate performance, voltage decay mitigation, and moisture resistance, showcasing its potential for practical utilization in energy storage applications.
High-Performance Ultraviolet Photodetector Based on Graphene Quantum Dots Decorated ZnO Nanorods/GaN Film Isotype Heterojunctions
A novel isotype heterojunction ultraviolet photodetector was fabricated by growing n-ZnO nanorod arrays on n-GaN thin films and then spin-coated with graphene quantum dots (GQDs). Exposed to UV illumination with a wavelength of 365 nm, the time-dependent photoresponse of the hybrid detectors manifests high sensitivity and consistent transients with a rise time of 100 ms and a decay time of 120 ms. Meanwhile, an ultra-high specific detectivity (up to ~ 10 12 Jones) and high photoresponsivity (up to 34 mA W −1 ) are obtained at 10 V bias. Compared to the bare heterojunction detectors, the excellent performance of the GQDs decorated n-ZnO/n-GaN heterostructure is attributed to the efficient immobilization of GQDs on the ZnO nanorod arrays. GQDs were exploited as a light absorber and act like an electron donor to effectively improve the effective carrier concentration in interfacial junction. Moreover, appropriate energy band alignment in GQDs decorated ZnO/GaN hybrids can also be a potential factor in facilitating the UV-induced photocurrent and response speed.
“All‐In‐One” integrated ultrathin SnS2@3D multichannel carbon matrix power high‐areal–capacity lithium battery anode
Construction of a thickness‐independent electrode with high active material mass loading is crucial for the development of high energy rechargeable lithium battery. Herein, we fabricate an all‐in‐one integrated SnS2@3D multichannel carbon matrix (SnS2@3DMCM) electrode with in‐situ growth of ultrathin SnS2 nanosheets inside the inner walls of three dimensional (3D) multichannels. The interconnected conductive carbon matrix derived from natural wood acts as an integrated porous current collector to avail the electrons transport and accommodate massive SnS2 nanosheets, while plenty of 3D aligned multichannels facilitate fast ions transport with electrode thickness‐independent even under high mass loading. As expected, the integrated SnS2@3DMCM electrode exhibits remarkable electrochemical lithium storage performance, such as exceptional high‐areal‐capacity of 6.4 mAh cm−2, high rate capability of 3 mAh cm−2 under current of 6.8 mA cm−2 (10 C), and stable cycling performance of 6.8 mA cm−2 with a high mass loading of 7 mg cm−2. The 3D integrated porous electrode constructing conveniently with the natural source paves new avenues towards future high‐performance lithium batteries. We construct an “All‐In‐One” integrated electrode with multichannel three‐dimensional carbon matrix confined ultrathin SnS2 nanosheet attaching fast lithium‐ion kinetics even under high active material mass loading over 7 mg cm−2. The as‐prepared SnS2@ multichannel carbon matrix composite electrode can endure a 6.8 mA cm−2 current density, delivering a specific capacity of 3 mAh cm−2 (522 mAh g−1).