Organic-Inorganic Hybrid Interfaces Enable the Preparation of Nitrogen-Doped Hollow Carbon Nanospheres as High-Performance Anodes for Lithium and Potassium-Ion Batteries.

An abundant hollow nanostructure is crucial for fast Li+ and K+ diffusion paths and sufficient electrolyte penetration, which creates a highly conductive network for ionic and electronic transport. In this study, we successfully developed a molecular-bridge-linked, organic-inorganic hybrid interface that enables the preparation of in situ nitrogen-doped hollow carbon nanospheres. Moreover, the prepared HCNSs, with high nitrogen content of up to 10.4%, feature homogeneous and regular morphologies. The resulting HCNSs exhibit excellent lithium and potassium storage properties when used as electrode materials. Specifically, the HCNS-800 electrode demonstrates a stable reversible discharge capacity of 642 mA h g-1 at 1000 mA g-1 after 500 cycles for LIBs. Similarly, the electrode maintains a discharge capacity of 205 mA h g-1 at 100 mA g-1 after 500 cycles for KIBs. Moreover, when coupled with a high-mass-loading LiFePO4 cathode to design full cells, the HCNS-800‖LiFePO4 cells provide a specific discharge capacity of 139 mA h g-1 at 0.1 C. These results indicate that the HCNS electrode has promising potential for use in high-energy and environmentally sustainable lithium-based and potassium-based batteries.

Controllable Preparation of Core-Shell Composites and Their Templated Hollow Carbons Based on a Well-Orchestrated Molecular Bridge-Linked Organic-Inorganic Hybrid Interface.

Controlling the interfacial effect is facing challenges because of the weak interactions between the inorganic and the organic materials. We found that the silane coupling agents with -NH2 groups (e.g., KH550) play a key role as a molecular bridge that links an inorganic silica template with an organic precursor (i.e., pyrrole) in the process of constructing a spherical silica core-polypyrrole shell structure. The molecular bridge is also suitable for inorganic core templates with cube or rod shapes for the construction of different core-shell structures. These template core-polymeric shell structures can be transformed into well-defined hollow carbons after carbonization and template removal. The outer diameter, hollow-core size, and carbon shell thickness of hollow carbon materials (e.g., hollow carbon spheres) could be facilely controlled by changing the template size or the pyrrole amount. We believe that our work will provide a guideline for the preparation of well-orchestrated carbon-based composites and their templated hollow carbons.

Thermoelectric transports in pristine and functionalized boron phosphide monolayers.

Recently, a new monolayer Group III-V material, two-dimensional boron phosphide (BP), has shown great potential for energy storage and energy conversion applications. We study the thermoelectric properties of BP monolayer as well as the effect of functionalization by first-principles calculation and Boltzmann transport theory. Combined with a moderate bandgap of 0.90 eV and ultra-high carrier mobility, a large ZT value of 0.255 at 300 K is predicted for two-dimensional BP. While the drastically reduced thermal conductivity in hydrogenated and fluorinated BP is favored for thermoelectric conversion, the decreased carrier mobility has limited the improvement of thermoelectric figure of merit.

Biomimetic Copper Forest Wick Enables High Thermal Conductivity Ultrathin Heat Pipe.

Electronic devices with high heat flux are currently facing heat dissipation problems. Heat pipes can be used as efficient heat spreaders to address this critical problem. However, as electronic devices become smaller, the space for heat dissipation is becoming ever so limited; hence, ultrathin heat pipes are desired. This study proposes a biomimetic copper forest wick for an ultrathin heat pipe (UTHP). It is made by a simple one-step electrodeposition process and appears as a natural forest structure with abundant Ω-like grooves. Capillary rise tests with ethanol were performed to characterize the capillary force of the wick structure. Compared to traditional sintered particles, this wick structure has a much higher capillary performance parameter, K/Reff. The biomimetic copper forest wick was used to fabricate a 0.6 mm thick UTHP. The UTHP was tested at different filling ratios; the optimum filling ratio was found to be about 71%. At a heating power of 6 W, the temperature difference between the condenser and evaporator was only 1.2 °C, with an effective thermal conductivity, λeff, up to 1.26 × 104 W m-1 K-1.

Carbon-coated SnO2 riveted on a reduced graphene oxide composite (C@SnO2/RGO) as an anode material for lithium-ion batteries.

The research on graphene-based anode materials for high-performance lithium-ion batteries (LIBs) has been prevalent in recent years. In the present work, carbon-coated SnO2 riveted on a reduced graphene oxide sheet composite (C@SnO2/RGO) was fabricated using GO solution, SnCl4, and glucose via a hydrothermal method after heat treatment. When the composite was exploited as an anode material for LIBs, the electrodes were found to exhibit a stable reversible discharge capacity of 843 mA h g-1 at 100 mA g-1 after 100 cycles with 99.5% coulombic efficiency (CE), and a specific capacity of 485 mA h g-1 at 1000 mA g-1 after 200 cycles; these values were higher than those for a sample without glucose (SnO2/RGO) and a pure SnO2 sample. The favourable electrochemical performances of the C@SnO2/RGO electrodes may be attributed to the special double-carbon structure of the composite, which can effectively suppress the volume expansion of SnO2 nanoparticles and facilitate the transfer rates of Li+ and electrons during the charge/discharge process.

Cauliflower-like Nickel with Polar Ni(OH)2/NiO x F y Shell To Decorate Copper Meshes for Efficient Oil/Water Separation.

In recent years, superhydrophilic and underwater superoleophobic membranes have shown promising results in advanced oil/water separation. However, these membranes still have some drawbacks, like tedious preparation process and instability, which hinder their application in oil/water separation. Accordingly, the development of a facile approach to prepare superhydrophilic membranes with excellent oil/water separation performance is still coveted. Here, a copper mesh decorated with cauliflower-like nickel (Cu mesh@CF-Ni) is synthesized via a facile one-step electrodeposition method. Due to the surface polar -OH and -O-Ni-F groups of the Ni(OH)2/NiO x F y shell of the cauliflower-like nickel (CF-Ni), this Cu mesh@CF-Ni displays superhydrophilic and underwater superoleophobic wettability. The results show that the Cu mesh@CF-Ni has excellent oil/water separation efficiency (higher than 99.2%) and ultrahigh water flux (around 20 L h-1 cm-2). Moreover, it also displays good stability in a 10 wt % NaCl solution and 1 M NaOH solution for oil/water separation. By introducing the CF-Ni with polar Ni(OH)2/NiO x F y components onto the surface of the materials via a simple electrodeposition method, the materials will acquire the capability to not only achieve oil/water separation but also realize many other applications, like self-cleaning, underwater bubble manipulation, and fog harvesting.

Predicted high thermoelectric performance in a two-dimensional indium telluride monolayer and its dependence on strain.

In recent years, another two-dimensional (2D) family, monolayer metal monochalcogenides (group IIIA-VIA), has attracted extensive attention. In this work, we adopt density functional theory (DFT) and the non-equilibrium Green's function (NEGF) method to systematically investigate the ballistic thermoelectric properties of the IIIA-VIA family, including GaS, GaSe, GaTe, InS, InSe, and InTe. Among others, the InTe monolayer possesses the highest figure of merit, ZT = 2.03 at 300 K, due to its ultra-low thermal conductance. Biaxial strain in the range of -10% (compressive) to 10% (tensile) is applied to the InTe monolayer and the strain-induced electronic and thermal transport properties are discussed. The maximum ZT (up to 2.7) for the InTe monolayer at 300 K is achieved under an 8% tensile strain.

Synthesis of MnCO3/Multiwalled Carbon Nanotube Composite as Anode Material for Lithium-Ion Batteries.

A MnCO3 /Multiwalled carbon nanotube (MnCO3/MWCNT) composite has been successfully fabricated by an in-suit hydrothermal method. When the MnCO3/MWCNT composite is applied as anode materials in lithium-ion batteries (LIBs), the electrodes exhibit a reversible capacity of 645 mA h g-1 at 100 mA g-1 after 80 cycles, reaching an initial coulombic efficiency (CE) of up to 60.6%. Furthermore, the as-prepared MnCO3/MWCNT composite displays more excellent rate performances than the pure multiwalled carbon nanotube (MWCNT) and pure MnCO3 particles. The reason is that the MnCO3 particles can be effectively connected by the MWCNT, thus enhancing the electrochemical performance of the MnCO3/MWCNT composite.

Preparation of novel two-stage structure MnO micrometer particles as lithium-ion battery anode materials.

MnO micrometer particles with a two-stage structure (composed of mass nanoparticles) were produced via a one-step hydrothermal method using histidine and potassium permanganate (KMnO4) as reagents, with subsequent calcination in a nitrogen (N2) atmosphere. When the MnO micrometer particles were utilized in lithium-ion batteries (LIBs) as anode materials, the electrode showed a high reversible specific capacity of 747 mA h g-1 at 100 mA g-1 after 100 cycles, meanwhile, the electrode presented excellent rate capability at various current densities from 100 to 2000 mA g-1 (∼203 mA h g-1 at 2000 mA g-1). This study developed a new approach to prepare two-stage structure micrometer MnO particles and the sample can be a promising anode material for lithium-ion batteries.

Theoretical design of a new family of two-dimensional topological insulators.

A new family of two-dimensional topological insulator, hydrogenated monolayer Pb2XY (X = Ga/In, Y = Sb/Bi), has been predicted using first-principles density functional theory. The electronic bulk band gap of the proposed systems can be induced in the presence of a spin-orbit coupling effect and its highest value (0.25 eV) was observed in the hydrogenated monolayer Pb2GaBi, which is suitable for practical application. Our simulation study points out that the nanoribbons derived from this new family harbor gapless edge channels. The non-trivial topological nature was further confirmed by calculating the Z2 topological invariant. These novel systems provide a new platform for topological phenomena observation and spintronic applications.

WSe2 nanoribbons: new high-performance thermoelectric materials.

In this work, for the first time, we systematically investigate the ballistic transport properties of WSe2 nanoribbons using first-principles methods. Armchair nanoribbons with narrow ribbon width are mostly semiconductive but the zigzag nanoribbons are metallic. Surprisingly, an enhancement in thermoelectric performance is discovered moving from monolayers to nanoribbons, especially armchair ones. The maximum room-temperature thermoelectric figure of merit of 2.2 for an armchair nanoribbon is discovered. This may be contributed to by the effects of the disordered edges, owing to the existence of dangling bonds at the ribbon edge. H-passivation has turned out to be an effective way to stabilize the edge atoms, which enhances the thermodynamic stability of the nanoribbons. In addition, after H-passivation, all of the armchair nanoribbons exhibit semiconductive properties with similar band gaps (∼1.3 eV). Our work provides instructional theoretical evidence for the application of armchair WSe2 nanoribbons as promising thermoelectric materials. The enhancement mechanism of the disordered edge effect can also encourage further exploration to achieve outstanding thermoelectric materials.

On the thermoelectric transport properties of graphyne by the first-principles method.

Graphyne, another two-dimensional carbon allotrope, has received increased attentions in recent years. By using the first-principles density functional calculations combined with the non-equilibrium Green's function formalism, we investigated the electronic, thermal, and thermoelectric transport properties of graphyne systematically and comparatively. It is found that the phonon thermal conductance of graphyne is greatly reduced compared to that of graphene in most temperature regions while larger than that of graphene at low temperatures, which is attributed to the different bond strengths and phonon spectra of graphyne and graphene. Due to the semiconductor property of graphyne, the thermoelectric power (TEP) is found to be one magnitude larger than that of graphene. Besides, distinct peak value regions of TEP in the contour of chemical potential and temperature are displayed for graphyne and graphene. Finally, the thermoelectric figure of merit (ZT) of graphyne is found to be much larger than that of graphene as a result of large TEP and greatly reduced thermal conductance in graphyne, which indicates preferred thermoelectric applications for graphyne.