MoS2 Hollow Multishelled Nanospheres Doped Fe Single Atoms Capable of Fast Phase Transformation for Fast‐charging Na‐ion Batteries

2024-03-06T13:08:09+00:00March 6th, 2024|Categories: Publications|Tags: , |

Low Na+ and electron diffusion kinetics severely restrain the rate capability of MoS2 as anode for sodium-ion batteries (SIBs). Slow phase transitions between 2H and 1T, and from NaxMoS2 to Mo and Na2S as well as the volume change during cycling, induce a poor cycling stability. Herein, an original Fe single atom doped MoS2 hollow multishelled structure (HoMS) is designed for the first time to address the above challenges. The Fe single atom in MoS2 promotes the electron transfer, companying with shortened charge diffusion path from unique HoMS, thereby achieving excellent rate capability. The strong adsorption with Na+ and self-catalysis of Fe single atom facilitates the reversible conversion between 2H and 1T, and from NaxMoS2 to Mo and Na2S. Moreover, the buffering effect of HoMS on volume change during cycling improves the cyclic stability. Consequently, the Fe single atom doped MoS2 quadruple-shelled sphere exhibits a high specific capacity of 213.3 mAh g-1 at an ultrahigh current density of 30 A g-1, which is superior to previously-reported results. Even at 5 A g-1, 259.4 mAh g-1 (83.68 %) was reserved after 500 cycles. Such elaborate catalytic site decorated HoMS is also promising to realize other “fast-charging” high-energy-density rechargeable batteries.

Published in: "Angewandte Chemie International Edition".

Unraveling the “Gap‐Filling” Mechanism of Multiple Charge Carriers in Aqueous Zn‐MoS2 Batteries

2024-03-05T13:08:19+00:00March 5th, 2024|Categories: Publications|Tags: , |

A novel MoS2/(reduced graphene quantum dots) hybrid featuring ultra-large interlayer spacing, superior electrical conductivity/hydrophilicity, and robust layered structure demonstrates highly reversible NH4 +/Zn2+/H+ co-insertion/extraction chemistry in aqueous Zn-based batteries, where NH4 + and H+ can serve as “gap-filling” ions to improve the utilization rate of active sites and screen electrostatic interactions to facilitate the Zn2+ diffusion. Abstract The utilization rate of active sites in cathode materials for Zn-based batteries is a key factor determining the reversible capacities. However, a long-neglected issue of the strong electrostatic repulsions among divalent Zn2+ in hosts inevitably causes the squander of some active sites (i.e., gap sites). Herein, we address this conundrum by unraveling the “gap-filling” mechanism of multiple charge carriers in aqueous Zn-MoS2 batteries. The tailored MoS2/(reduced graphene quantum dots) hybrid features an ultra-large interlayer spacing (2.34 nm), superior electrical conductivity/hydrophilicity, and robust layered structure, demonstrating highly reversible NH4 +/Zn2+/H+ co-insertion/extraction chemistry in the 1 M ZnSO4+0.5 M (NH4)2SO4 aqueous electrolyte. The NH4 + and H+ ions can act as gap fillers to fully utilize the active sites and screen electrostatic interactions to accelerate the Zn2+ diffusion. Thus, unprecedentedly high rate capability (439.5 and 104.3 mAh g−1 at 0.1 and 30 A g−1, respectively) and ultra-long cycling life (8000 cycles) are achieved.

Published in: "Angewandte Chemie International Edition".

Ligand Modulation of Active Sites to Promote Cobalt‐Doped 1T‐MoS2 Electrocatalytic Hydrogen Evolution in Alkaline Media

2023-11-22T13:07:55+00:00November 22nd, 2023|Categories: Publications|Tags: |

A synergistic ligand modulation plus cobalt doping strategy is applied to modulate the orbital hybridization of 1T-MoS2 catalyst via CoMo-MOF precursors. The polydentate 1,2-bis(4-pyridyl)ethane (bpe) ligand can stably link with 1T-MoS2 layers to achieve expanded interlayer spacing, which promotes the joint participation of highly efficient active sites in the basal plane and the interlayer in alkaline HER processes. Abstract Highly efficient hydrogen evolution reaction (HER) electrocatalyst will determine the mass distributions of hydrogen-powered clean technologies, while still faces grand challenges. In this work, a synergistic ligand modulation plus Co doping strategy is applied to 1T−MoS2 catalyst via CoMo-metal-organic frameworks precursors, boosting the HER catalytic activity and durability of 1T−MoS2. Confirmed by Cs corrected transmission electron microscope and X-ray absorption spectroscopy, the polydentate 1,2-bis(4-pyridyl)ethane ligand can stably link with two-dimensional 1T−MoS2 layers through cobalt sites to expand interlayer spacing of MoS2 (Co−1T−MoS2-bpe), which promotes active site exposure, accelerates water dissociation, and optimizes the adsorption and desorption of H in alkaline HER processes. Theoretical calculations indicate the promotions in the electronic structure of 1T−MoS2 originate in the formation of three-dimensional metal-organic constructs by linking π-conjugated ligand, which weakens the hybridization between Mo-3d and S-2p orbitals, and in turn makes S-2p orbital more suitable for hybridization with H-1s orbital. Therefore, Co−1T−MoS2-bpe exhibits excellent stability and exceedingly low overpotential for alkaline HER (118 mV at 10 mA cm−2). In addition, integrated into an anion-exchange membrane water electrolyzer, Co−1T−MoS2-bpe is much superior to the Pt/C catalyst at the large current densities. This study provides a feasible ligand

Published in: "Angewandte Chemie International Edition".

Photo‐Controlled Gating of Selective Bacterial Membrane Interaction and Enhanced Antibacterial Activity for Wound Healing

2023-11-14T13:08:28+00:00November 14th, 2023|Categories: Publications|Tags: |

Reversible biointerfaces are essential for on-demand molecular recognition to regulate stimuli responsive bioactivity such as specific interactions with cell membrane. The reversibility on a single platform allows the smart material to kill pathogens or attach/detach cells. Herein, we introduce a 2D-MoS2 functionalized with cationic azobenzene that interacts selectively with either Gram-positive or Gram-negative bacteria in a light-gated fashion. The trans conformation (trans-Azo-MoS2) selectively kills Gram-negative bacteria, whereas the cis form (cis-Azo-MoS2) under UV light, exhibits antibacterial activity against Gram-positive strain. The mechanistic investigation indicates that the cis-Azo-MoS2 selectively binds with bacterial membrane of Gram-positive bacteria than trans-Azo-MoS2. In case of Gram-negative bacteria, trans-Azo-MoS2 internalizes more efficiently than cis-Azo-MoS2 and generate intracellular ROS to kill the bacteria. While the trans-Azo-MoS2exhibits strong electrostatic interactions and internalizes faster into Gram-negative bacterial cells, cis-Azo-MoS2 primarily interacts with Gram-positive bacteria through hydrophobic and H-bonding interactions. The difference in molecular mechanism leads to photo-controlled Gram-selectivity and enhanced antibacterial activity. We found strain-specific and high bactericidal activity (minimal bactericidal concentration, 0.65 ug/ml) with low cytotoxicity, which we extended to wound healing applications. This methodology provides a single platform for efficiently switching between conformers to reversibly control the strain selective bactericidal activity regulated by light.

Published in: "Angewandte Chemie International Edition".

Inside Back Cover: Boosting CO2 Hydrogenation to Formate over Edge‐Sulfur Vacancies of Molybdenum Disulfide (Angew. Chem. Int. Ed. 45/2023)

2023-11-01T09:25:49+00:00November 1st, 2023|Categories: Publications|Tags: |

Sn-based perovskite oxides have shown intriguing potential in CO2 electroreduction. In their Research Article (e202307086), Jiawei Zhu and co-workers report an effective strategy to promote CO2-to-HCOOH conversion of Sn-based perovskite oxides by A-site-radius-controlled Sn−O bond lengths. With the Ba1−xSrxSnO3 (x from 0 to 1) series as proof-of-concept catalysts, it is demonstrated that their activity/selectivity for HCOOH featured a volcano-type dependence on the Sn−O bond lengths, with a maximum point corresponding to Ba0.5Sr0.5SnO3.

Published in: "Angewandte Chemie International Edition".

Boosting CO2 Hydrogenation to Formate over Edge‐Sulfur Vacancies of Molybdenum Disulfide

2023-11-01T09:24:59+00:00November 1st, 2023|Categories: Publications|Tags: |

Edge-rich MoS2 is presented as a promising catalyst for CO2 hydrogenation to formate with superior activity and stability. The selective formation of formate is enabled by using surface OH* and H* species from H2O dissociation on the edge-sulfur vacancies as moderate hydrogenating agents. Abstract Synthesis of formate from hydrogenation of carbon dioxide (CO2) is an atom-economic reaction but is confronted with challenges in developing high-performance non-precious metal catalysts for application of the process. Herein, we report a highly durable edge-rich molybdenum disulfide (MoS2) catalyst for CO2 hydrogenation to formate at 200 °C, which delivers a high selectivity of over 99 % with a superior turnover frequency of 780.7 h−1 surpassing those of previously reported non-precious metal catalysts. Multiple experimental characterization techniques combined with theoretical calculations reveal that sulfur vacancies at MoS2 edges are the active sites and the selective production of formate is enabled via a completely new water-mediated hydrogenation mechanism, in which surface OH* and H* species in dynamic equilibrium with water serve as moderate hydrogenating agents for CO2 with residual O* reduced by hydrogen. This study provides a new route for developing low-cost high-performance catalysts for CO2 hydrogenation to formate.

Published in: "Angewandte Chemie International Edition".

Universal Sub‐Nanoreactor Strategy for Synthesis of Yolk‐Shell MoS2 Supported Single Atom Electrocatalysts toward Robust Hydrogen Evolution Reaction

2023-06-21T13:08:16+00:00June 21st, 2023|Categories: Publications|Tags: |

The coordination structure determines the electrocatalytic performances of single atom catalysts (SACs), while it remains a challenge to precisely regulate their spatial location and coordination environment. Herein, we report a universal sub-nanoreactor strategy for synthesis of yolk–shell MoS2 supported single atom electrocatalysts with dual–anchored microenvironment of vacancy-enriched MoS2 and intercalation carbon toward robust hydrogen-evolution reaction. Theoretical calculations reveal that the “E-Lock” and “E-Channel” are conducive to stabilize and activate metal single atoms. A group of SACs is subsequently produced with the assistance of sulfur vacancy and intercalation carbon in the yolk–shell sub-nanoreactor. The optimized C-Co-MoS2 yields the lowest overpotential (η10=17 mV) compared with previously reported MoS2-based electrocatalysts to date, and also affords a 5‒9 fold improvement in activity even comparing with those as-prepared single–anchored analogues. Theoretical results and in-situ characterizations unveil its active center and durability. This work provides a universal pathway to design efficient catalysts for electro-refinery.

Published in: "Angewandte Chemie International Edition".

Directly Imaging and Regulating the Nanoscale Inhomogeneity of S‐Vacancies in Molybdenum Disulfide Monolayer during Electrocatalytic Hydrogen Evolution

2023-06-14T13:07:59+00:00June 14th, 2023|Categories: Publications|Tags: |

The study of electron transfer event on two-dimensional (2D) layered transition metal dichalcogenides has attracted tremendous attentions attributing to their promising applications in electrochemical devices. Herein, we demonstrate an opto-electrochemical strategy to directly map and regulate electron transfer event on molybdenum disulfide (MoS2) monolayer by combining bright field (BF) imaging technique with electrochemical modulation. The heterogeneity of electrochemical activity on MoS2 monolayer down to nanoscale is resolved spatiotemporally. The thermodynamics of MoS2 monolayer is measured during electrocatalytic hydrogen evolution, and the Arrhenius correlations are obtained. We validate that the defect generation engineered by oxygen plasma bombardment dramatically enhances the local electrochemical activity of MoS2 monolayer, which can be attributed to point defects of S-vacancies as evidenced. Furthermore, by comparing the difference of electron transfer event on MoS2 with various layers, the interlayer coupling effect is uncovered. This study represents a facile method to image the heterogeneity of electrochemical properties for nanomaterials with atomic thickness and regulate the local activity within the plane by extrinsic factors. It also has potential applications in the design and evaluation of high-performance layered electrochemical systems down to nanoscale.

Published in: "Angewandte Chemie International Edition".

Chirality‐Dependent Reprogramming of Macrophages by Chiral Nanozymes

2023-06-13T13:07:57+00:00June 13th, 2023|Categories: Publications|Tags: |

It is known that extracellular free radical reactive oxygen species (ROS) rather than intracellular ROS plays a non-substitutable role in regulation of tumor-suppressing (M1) tumor-associated macrophages (TAMs) polarization. However, most therapeutic nanoplatforms mainly provide intracellular ROS and exhibit insufficient accumulation near TAMs, which strongly limits the macrophage-based immunotherapeutic effects. Here we design and synthesize chiral MoS2/CoS2 nanozymes with peroxidase (POD)-like and catalase (CAT)-like activities to efficiently modulate TAMs polarization and reverse tumor immunosuppression by harnessing their chirality-specific interactions with biological systems. MoS2/CoS2 nanoparticles coordinated with d-chirality (d -NPs, right-handed) show improved pharmacokinetics with longer circulating half-life and higher tumor accumulation compared with their l (left-handed)- and dl (racemate)-counterparts. Further, d-NPs can escape from macrophage uptake in the tumor microenvironment (TME) with the aid of cell-unpreferred opposite chirality and act as extracellular hydroxyl radicals (•OH) and oxygen (O2) generators to efficiently repolarize TAMs into M1 phenotype. On the contrary, l-NPs showed high cellular uptake due to chirality-driven homologous adhesion between l-NPs and macrophage membrane, leading to limited M1 polarization performance. As the first example for developing chiral nanozymes as extracellular-localized ROS generators to reprogram TAMs for cancer immunotherapy, this study opens an avenue for applications of chiral nanozymes in immunomodulation.

Published in: "Angewandte Chemie International Edition".

Reversing Free‐Electron Transfer of MoS2+x Cocatalyst for Optimizing Antibonding‐Orbital Occupancy Enables High Photocatalytic H2 Evolution

2023-06-10T13:08:11+00:00June 10th, 2023|Categories: Publications|Tags: , |

To create a beneficial transfer direction for cultivating moderate hydrogen-atom adsorption/desorption on a co-catalyst, an electron-reversal strategy is proposed that optimizes the antibonding-orbital occupancy. The embedded Au can reverse the free-electron transfer to MoS2+x to form electron-rich S(2+δ)−, which causes an increased antibonding-orbital occupancy, thus weakening S−Hads bonds for photocatalytic H2 evolution. Abstract The interaction between a co-catalyst and photocatalyst usually induces spontaneous free-electron transfer between them, but the effect and regulation of the transfer direction on the hydrogen-adsorption energy of the active sites have not received attention. Herein, to steer the free-electron transfer in a favorable direction for weakening S−Hads bonds of sulfur-rich MoS2+x , an electron-reversal strategy is proposed for the first time. The core–shell Au@MoS2+x cocatalyst was constructed on TiO2 to optimize the antibonding-orbital occupancy. Research results reveal that the embedded Au can reverse the electron transfer to MoS2+x to generate electron-rich S(2+δ)− active sites, thus increasing the antibonding-orbital occupancy of S−Hads in the Au@MoS2+x cocatalyst. Consequently, the increase in the antibonding-orbital occupancy effectively destabilizes the H 1s-p antibonding orbital and weakens the S−Hads bond, realizing the expedited desorption of Hads to rapidly generate a lot of visible H2 bubbles. This work delves deep into the latent effect of the photocatalyst carrier on cocatalytic activity.

Published in: "Angewandte Chemie International Edition".

High‐throughput Synthesis of Solution‐Processable van der Waals Heterostructures through Electrochemistry

2023-06-07T13:08:21+00:00June 7th, 2023|Categories: Publications|Tags: , , , , |

A general method is demonstrated for the preparation of high-quality van der Waals heterostructures in solution through an electrochemical strategy. The produced van der Waals heterostructures exhibit strong interlayer coupling, extraordinary structural integrity, large lateral dimension and good optoelectronic properties. Abstract Two-dimensional van der Waals heterostructures (2D vdWHs) have recently gained widespread attention because of their abundant and exotic properties, which open up many new possibilities for next-generation nanoelectronics. However, practical applications remain challenging due to the lack of high-throughput techniques for fabricating high-quality vdWHs. Here, we demonstrate a general electrochemical strategy to prepare solution-processable high-quality vdWHs, in which electrostatic forces drive the stacking of electrochemically exfoliated individual assemblies with intact structures and clean interfaces into vdWHs with strong interlayer interactions. Thanks to the excellent combination of strong light absorption, interfacial charge transfer, and decent charge transport properties in individual layers, thin-film photodetectors based on graphene/In2Se3 vdWHs exhibit great promise for near-infrared (NIR) photodetection, owing to a high responsivity (267 mA W−1), fast rise (72 ms) and decay (426 ms) times under NIR illumination. This approach enables various hybrid systems, including graphene/In2Se3, graphene/MoS2 and graphene/MoSe2 vdWHs, providing a broad avenue for exploring emerging electronic, photonic, and exotic quantum phenomena.

Published in: "Angewandte Chemie International Edition".

Dual‐Functional Z‐Scheme TiO2@MoS2@C Multi‐Heterostructures for Photo‐Driving Ultra‐Fast Sodium Ion Storage

2023-05-29T13:08:25+00:00May 29th, 2023|Categories: Publications|Tags: , , |

Exploiting dual-functional photoelectrodes to harvest and store solar energy is a challenging but efficient way of achieving renewable energy utilization. Herein, TiO2@MoS2@C multi-heterostructures with photoelectric conversion and electronic transmission interfaces are designed as dual-functional photoelectrode for ultra-fast sodium ion storage. When assembled to photo sodium ion battery (photo-SIB), its capacity increases to 444.1 mAh g-1 with a high photo-conversion efficiency of 0.71% switching from dark to visible light at 2.0 A g-1. Remarkably, the photo-SIB can be recharged only by light and provide a striking capacity of 231.4 mAh g-1. Experimental and theoretical results confirm the multi-heterostructures can enhance sodium ion storage kinetics, ensure structural stability, and facilitate photo-excited carrier separation and transmission under light. This work presents a brand-new strategy to design dual-functional photoelectrodes for efficient solar harvesting and storage.

Published in: "Angewandte Chemie International Edition".

Dual‐Functional Z‐Scheme TiO2@MoS2@C Multi‐Heterostructures for Photo‐Driving Ultra‐Fast Sodium Ion Storage

2023-05-28T08:36:08+00:00May 28th, 2023|Categories: Publications|Tags: , , |

Exploiting dual-functional photoelectrodes to harvest and store solar energy is a challenging but efficient way of achieving renewable energy utilization. Herein, TiO2@MoS2@C multi-heterostructures with photoelectric conversion and electronic transmission interfaces are designed as dual-functional photoelectrode for ultra-fast sodium ion storage. When assembled to photo sodium ion battery (photo-SIB), its capacity increases to 444.1 mAh g-1 with a high photo-conversion efficiency of 0.71% switching from dark to visible light at 2.0 A g-1. Remarkably, the photo-SIB can be recharged only by light and provide a striking capacity of 231.4 mAh g-1. Experimental and theoretical results confirm the multi-heterostructures can enhance sodium ion storage kinetics, ensure structural stability, and facilitate photo-excited carrier separation and transmission under light. This work presents a brand-new strategy to design dual-functional photoelectrodes for efficient solar harvesting and storage.

Published in: "Angewandte Chemie International Edition".

Spectroscopic Evidence for Interfacial Charge Separation and Recombination in Graphene-MoS2 Vertical Heterostructures. (arXiv:2304.08724v1 [physics.optics])

2023-04-19T02:30:22+00:00April 19th, 2023|Categories: Publications|Tags: , , |

Vertical van der Waals (vdW) heterostructures consisting of graphene (Gr) and transition metal dichalcogenides (TMDs) have created a fascinating platform for exploring optical and electronic properties in the two-dimensional limit. Previous study has revealed the ultrafast formation of interfacial excitons and the exciton dynamics in the Gr/MoS2 heterostructure. However, a fully understanding of interfacial charge separation and the subsequent dynamics in graphene-based heterostructures remains elusive. Here, we investigate the carrier dynamics of Gr-MoS2 (including Gr/MoS2 and MoS2/Gr stacking sequences) heterostructures under different photoexcitation energies and stacking sequences by comprehensive ultrafast means, including time-resolved terahertz spectroscopy (TRTS), terahertz emission spectroscopy (TES) and transient absorption spectroscopy (TAS). We demonstrate that the Gr/MoS2 heterostructure generates hot electron injection from graphene into the MoS2 layer with photoexcitation of sub-A-exciton of MoS2, while the interfacial charge separation in the MoS2/Gr could be partially blocked by the electric field of substrate. Charge transfer (CT) occurs in same directions for the Gr-MoS2 heterostructures with opposite stacking order, resulting in the opposite orientations of the interfacial photocurrent, as directly demonstrated by the terahertz (THz) emission. Moreover, we demonstrate that the recombination time of interfacial charges after CT is on a timescale of 18 ps to 1 ns, depending on the density of defect states in MoS2 layer. This work provides a comprehensive and unambiguous picture of the interfacial charge dynamics of graphene-based heterostructures, which is essential for developing Gr/TMDs based optoelectronic devices.

Published in: "arXiv Material Science".

Tuning the lattice thermal conductivity in van-der-Waals structures through rotational (dis)ordering. (arXiv:2304.06978v1 [cond-mat.mtrl-sci])

2023-04-17T02:29:35+00:00April 17th, 2023|Categories: Publications|Tags: |

It has recently been demonstrated that MoS2 with irregular interlayer rotations can achieve an extreme anisotropy in the lattice thermal conductivity (LTC), which is for example of interest for applications in waste heat management in integrated circuits. Here, we show by atomic scale simulations based on machine-learned potentials that this principle extends to other two-dimensional materials including C and BN. In all three materials introducing rotational disorder drives the through-plane LTC to the glass limit, while the in-plane LTC remains almost unchanged compared to the ideal bulk materials. We demonstrate that the ultralow through-plane LTC is connected to the collapse of their transverse acoustic modes in the through-plane direction. Furthermore, we find that the twist angle in periodic moir’e structures representing rotational order provides an efficient means for tuning the through-plane LTC that operates for all chemistries considered here. The minimal through-plane LTC is obtained for angles between 1 and 4 degree depending on the material, with the biggest effect in MoS2. The angular dependence is correlated with the degree of stacking disorder in the materials, which in turn is connected to the slip surface. This provides a simple descriptor for predicting the optimal conditions at which the LTC is expected to become minimal.

Published in: "arXiv Material Science".

Electronic properties of 2{it H}-stacking bilayer MoS$_2$ measured by terahertz time-domain spectroscopy. (arXiv:2304.06927v1 [cond-mat.mtrl-sci])

2023-04-17T02:29:30+00:00April 17th, 2023|Categories: Publications|Tags: |

Bilayer (BL) molybdenum disulfide (MoS$_2$) is one of the most important electronic structures not only in valleytronics but also in realizing twistronic systems on the basis of the topological mosaics in Moir’e superlattices. In this work, BL MoS$_2$ on sapphire substrate with 2$H$-stacking structure is fabricated. We apply the terahertz (THz) time-domain spectroscopy (TDS) for examining the basic optoelectronic properties of this kind of BL MoS$_2$. The optical conductivity of BL MoS$_2$ is obtained in temperature regime from 80 to 280 K. Through fitting the experimental data with the theoretical formula, the key sample parameters of BL MoS$_2$ can be determined, such as the electron density, the electronic relaxation time and the electronic localization factor. The temperature dependence of these parameters is examined and analyzed. We find that, similar to monolayer (ML) MoS$_2$, BL MoS$_2$ with 2$H$-stacking can respond strongly to THz radiation field and show semiconductor-like optoelectronic features. The theoretical calculations using density functional theory (DFT) can help us to further understand why the THz optoelectronic properties of BL MoS$_2$ differ from those observed for ML MoS$_2$. The results obtained from this study indicate that the THz TDS can be applied suitably to study the optoelectronic properties of BL MoS$_2$ based twistronic systems for novel applications as optical and optoelectronic materials and devices.

Published in: "arXiv Material Science".

Resolidified Chalcogen Precursors for High‐Quality 2D Semiconductor Growth

2023-04-11T10:21:19+00:00April 11th, 2023|Categories: Publications|Tags: , , , |

Two-dimensional (2D) semiconductors including transition metal dichalcogenides (TMDCs) have gained attention in optoelectronics for their extraordinary properties. However, the large amount and locally distributed lattice defects affect the optical properties of 2D TMDCs, and the defects originate from unstable factors in the synthesis process. In this work, we develop a method of pre-melting and resolidification of chalcogen precursors (sulfur and selenium), namely resolidified chalcogen, as precursor for the chemical vapor deposition growth of TMDCs with ultrahigh quality and uniformity. Taking WS2 as an example, the monolayer WS2 shows uniform fluorescence intensity and a small full-width at half-maximum of photoluminescence peak at low temperatures with an average value of 13.6 ± 1.9 meV. The defect densities at the interior and edge region are both low and comparable, i.e., (9 ± 3) × 1012 cm-2 and (10 ± 4) × 1012 cm-2, indicating its high structural quality and uniformity. This method is universal in growing high quality monolayer MoS2, WSe2, MoSe2, and will benefit their applications.

Published in: "Angewandte Chemie International Edition".

Selective Production of CO from Organic Pollutants by Coupling Piezocatalysis and Advanced Oxidation Processes

2023-03-26T13:07:54+00:00March 26th, 2023|Categories: Publications|Tags: |

To date, the chemical conversion of organic pollutants into value-added chemical feedstocks rather than CO2 remains a major challenge. Herein, we successfully develop a piezocatalysis coupling advanced oxidation process (AOP) system for achieving the conversion of various organic pollutants to CO. The CO product stems from the specific process in which organics are first oxidized to carbonate through peroxymonosulfate (PMS)-based AOPs, and then the as-obtained carbonate is converted into CO by piezoelectric reduction under ultrasonic (US) vibration by using a Co3S4/MoS2 catalyst. Experiments and DFT calculations show that the introduction of Co3S4 can not only effectively promote the transfer and utilization of piezoelectric electrons but also realize the highly selective conversion from carbonate to CO. The Co3S4/MoS2/PMS system has achieved the selective generation of CO in the actual complex wastewater treatment for the first time, indicating its potential practical application prospect.

Published in: "Angewandte Chemie International Edition".

Open-tunneled oxides as intercalation host for multivalent ion (Ca and Al) batteries: A DFT study. (arXiv:2303.12301v1 [cond-mat.mtrl-sci])

2023-03-23T02:29:33+00:00March 23rd, 2023|Categories: Publications|Tags: , , |

Lithium-ion batteries (LIBs) are ubiquitous in everyday applications. However, Lithium (Li) is a limited resource on the planet and is therefore not sustainable. As an alternative to lithium, earth-abundant and cheaper multivalent metals such as aluminum (Al) and calcium (Ca) have been actively researched in battery systems. However, finding suitable intercalation hosts for multivalent-ion batteries is urgently needed. Open-tunneled oxides are a particular category of microparticles distinguished by the presence of integrated one-dimensional channels or nanopores. This work focuses on two promising open-tunnel oxides, viz: Niobium Tungsten Oxide (NTO) and Molybdenum Vanadium Oxide (MoVO). We find that the MoVO structure can adsorb greater numbers of multivalent ions than NTO due to its larger surface area and different shapes. The MoVO structure can adsorb Ca, Li, and Al ions with adsorption potential at around 4 to 5 eV. However, the adsorption potential for hexagonal channels of Al ion drops to 1.73 eV because of less channel area. NTO structure has an insertion/adsorption potential of 4.4 eV, 3.4 eV, and 0.9 eV for one Li, Ca, and Al, respectively. In general, Ca ion is more adsorbable than Al ion in both MoVO and NTO structures. Bader charge analysis and charge density plot reveals the role of charge transfer and ion size on the insertion of multivalent ions such as Ca and Al into MoVO and NTO systems. Our results provide general guidelines to explore other multivalent ions for battery applications.

Published in: "arXiv Material Science".

Landauer-QFLPS model for mixed Schottky-Ohmic contact two-dimensional transistors. (arXiv:2303.11107v1 [physics.app-ph])

2023-03-21T04:30:22+00:00March 21st, 2023|Categories: Publications|Tags: , |

Two-dimensional material-based field effect transistors (2DM-FETs) are playing a revolutionary role in electronic devices. However, after years of development, no device model can match the Pao-Sah model for standard silicon-based transistors in terms of physical accuracy and computational efficiency to support large-scale integrated circuit design. One remaining critical obstacle is the contacts of 2DM-FETs. In order to self-consistently include the contact effect in the current model, it is necessary to perform self-consistent calculations, which is a fatal flaw for applications that prioritize efficiency. Here, we report that the Landauer-QFLPS model effectively overcomes the above contradiction, where QFLPS means quasi-Fermi-level phase space theory. By connecting the physical pictures of the contact and the intrinsic channel part, we have successfully derived a drain-source current formula including the contact effect. To verify the model, we prepared transistors based on two typical 2DMs, black phosphorus (BP) and molybdenum disulfide (MoS2), the former having ambipolar transport and the latter showing electron-dominant unipolar transport. The proposed new formula could describe both 2DM-FETs with Schottky or Ohmic contacts. Moreover, compared with traditional methods, the proposed model has the advantages of accuracy and efficiency, especially in describing non-monotonic drain conductance characteristics, because the contact effect is self-consistently and compactly packaged as an exponential term. More importantly, we also examined the model at the circuit level. Here, we fabricated a three-bit threshold inverter quantizer circuit based on ambipolar-BP process and experimentally demonstrated that the model can accurately predict the circuit performance. This industry-benign 2DM-FET model is supposed to be

Published : "arXiv Mesoscale and Nanoscale Physics".

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