Ting Liao

Hybrid graphene and graphitic carbon nitride nanocomposite: gap opening, electron-hole puddle, interfacial charge transfer, and enhanced visible light response

Opening up a band gap and finding a suitable substrate material are two big challenges for building graphene-based nanodevices. Using state-of-the-art hybrid density functional theory incorporating long-range dispersion corrections, we investigate the interface between optically active graphitic carbon nitride (g-C(3)N(4)) and electronically active graphene. We find an inhomogeneous planar substrate (g-C(3)N(4)) promotes electron-rich and hole-rich regions, i.e., forming a well-defined electron-hole puddle, on the supported graphene layer. The composite displays significant charge transfer from graphene to the g-C(3)N(4) substrate, which alters the electronic properties of both components. In particular, the strong electronic coupling at the graphene/g-C(3)N(4) interface opens a 70 meV gap in g-C(3)N(4)-supported graphene, a feature that can potentially allow overcoming the graphenes band gap hurdle in constructing field effect transistors. Additionally, the 2-D planar structure of g-C(3)N(4) is free of dangling bonds, providing an ideal substrate for graphene to sit on. Furthermore, when compared to a pure g-C(3)N(4) monolayer, the hybrid graphene/g-C(3)N(4) complex displays an enhanced optical absorption in the visible region, a promising feature for novel photovoltaic and photocatalytic applications.

Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets

Two-dimensional (2D) transition metal oxide systems present exotic electronic properties and high specific surface areas, and also demonstrate promising applications ranging from electronics to energy storage. Yet, in contrast to other types of nanostructures, the question as to whether we could assemble 2D nanomaterials with an atomic thickness from molecules in a general way, which may give them some interesting properties such as those of graphene, still remains unresolved. Herein, we report a generalized and fundamental approach to molecular self-assembly synthesis of ultrathin 2D nanosheets of transition metal oxides by rationally employing lamellar reverse micelles. It is worth emphasizing that the synthesized crystallized ultrathin transition metal oxide nanosheets possess confined thickness, high specific surface area and chemically reactive facets, so that they could have promising applications in nanostructured electronics, photonics, sensors, and energy conversion and storage devices.

Fly-eye inspired superhydrophobic anti-fogging inorganic nanostructures

Fly-eye bio-inspired inorganic nanostructures are synthesized via a two-step self-assembly approach, which have low contact angle hysteresis and excellent anti-fogging properties, and are promising candidates for anti-freezing/fogging materials to be applied in extreme and hazardous environments.

First-principles prediction of low shear-strain resistance of Al3BC3: A metal borocarbide containing short linear BC2 units

The elastic stiffness and shear deformation mode of Al3BC3, a metal borocarbide containing linear C–B–C units, are studied based on the first-principles total energy calculations. The predominant effect of C–B–C units on mechanical properties is reported by leading to low shear modulus. The low shear-strain resistance originates from the deformation mode as follows: the rigid linear C–B–C units tilt with respect to the c direction easily, and the corner-sharing Al5C bipyramid slabs simultaneously slide along the basal plane with low resistance. The proposed deformation mode may be universal for the ternary metal borocarbides family containing short linear C–B–C units.

Zr4+ Doping in Li4Ti5O12 Anode for Lithium‐Ion Batteries: Open Li+ Diffusion Paths through Structural Imperfection

One-dimensional nanomaterials have short Li(+) diffusion paths and promising structural stability, which results in a long cycle life during Li(+) insertion and extraction processes in lithium rechargeable batteries. In this study, we fabricated one-dimensional spinel Li4Ti5O12 (LTO) nanofibers using an electrospinning technique and studied the Zr(4+) doping effect on the lattice, electronic structure, and resultant electrochemical properties of Li-ion batteries (LIBs). Accommodating a small fraction of Zr(4+) ions in the Ti(4+) sites of the LTO structure gave rise to enhanced LIB performance, which was due to structural distortion through an increase in the average lattice constant and thereby enlarged Li(+) diffusion paths rather than changes to the electronic structure. Insulating ZrO2 nanoparticles present between the LTO grains due to the low Zr(4+) solubility had a negative effect on the Li(+) extraction capacity, however. These results could provide key design elements for LTO anodes based on atomic level insights that can pave the way to an optimal protocol to achieve particular functionalities.

Two-dimensional metal oxide nanomaterials for next-generation rechargeable batteries

The exponential increase in research focused on two-dimensional (2D) metal oxides has offered an unprecedented opportunity for their use in energy conversion and storage devices, especially for promising next-generation rechargeable batteries, such as lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs), as well as some post-lithium batteries, including lithium-sulfur batteries, lithium-air batteries, etc. The introduction of well-designed 2D metal oxide nanomaterials into next-generation rechargeable batteries has significantly enhanced the performance of these energy-storage devices by providing higher chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier-/charge-transport kinetics, which have greatly promoted the development of nanotechnology and the practical application of rechargeable batteries. Here, the recent progress in the application of 2D metal oxide nanomaterials in a series of rechargeable LIBs, NIBs, and other post lithium-ion batteries is reviewed relatively comprehensively. Current opportunities and future challenges for the application of 2D nanomaterials in energy-storage devices to achieve high energy density, high power density, stable cyclability, etc. are summarized and outlined. It is believed that the integration of 2D metal oxide nanomaterials in these clean energy devices offers great opportunities to address challenges driven by increasing global energy demands.

Electronic coupling and catalytic effect on H2 evolution of MoS2/graphene nanocatalyst.

Inorganic nano-graphene hybrid materials that are strongly coupled via chemical bonding usually present superior electrochemical performance. However, how the chemical bond forms and the synergistic catalytic mechanism remain fundamental questions. In this study, the chemical bonding of the MoS2 nanolayer supported on vacancy mediated graphene and the hydrogen evolution reaction of this nanocatalyst system were investigated. An obvious reduction of the metallic state of the MoS2 nanolayer is noticed as electrons are transferred to form a strong contact with the reduced graphene support. The missing metallic state associated with the unsaturated atoms at the peripheral sites in turn modifies the hydrogen evolution activity. The easiest evolution path is from the Mo edge sites, with the presence of the graphene resulting in a decrease in the energy barrier from 0.17 to 0.11 eV. Evolution of H2 from the S edge becomes more difficult due to an increase in the energy barrier from 0.43 to 0.84 eV. The clarification of the chemical bonding and catalytic mechanisms for hydrogen evolution using this strongly coupled MoS2/graphene nanocatalyst provide a valuable source of reference and motivation for further investigation for improved hydrogen evolution using chemically active nanocoupled systems.

First-principles investigation of intrinsic defects and (N, O) impurity atom stimulated Al vacancy in Ti2AlC

We use first-principles calculations to study the energetics of intrinsic defects in Ti 2 AlC and the effect of N or O impurity atoms on the generation of Al vacancies. The insertion of impurity atoms lowers the vacancy formation energy of its neighboring Al. The formation of Al vacancies is related to the experimental observations of growth of AlN or Al 2 O 3 nanowires and nanofibers on the surface of Ti 2 AlC. Since the growth of these nanostructures is controlled by the generation and migration of intrinsic defects, we propose that a tunable method for synthesis of such nanostructures is possible by controlling impurities.

Strategies for designing metal oxide nanostructures

There has been exponential growth in research activities on nanomaterials and nanotechnology for applications in emerging technologies and sustainable energy in the past decade. The properties of nanomaterials have been found to vary in terms of their shapes, sizes, and number of nanoscale dimensions, which have also further boosted the performance of nanomaterial-based electronic, catalytic, and sustainable energy conversion and storage devices. This reveals the importance and, indeed, the linchpin role of nanomaterial synthesis for current nanotechnology and high-performance functional devices. In this review, we provide an overview of the synthesis strategies for designing metal oxide nanomaterials in zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) forms, particularly of the selected typical metal oxides TiO2, SnO2 and ZnO. The pros and cons of the typical synthetic methods and experimental protocols are reviewed and outlined. This comprehensive review gives a broad overview of the synthetic strategies for designing “property-on-demand” metal oxide nanostructures to further advance current nanoscience and nanotechnology.摘要在过去十几年里, 纳米材料和纳米技术在新兴技术和新能源方面的应用获得了长足发展. 纳米材料的性能由于其异于块体材料的独特性能完全改变了人们对材料性质的认识, 并且极大地提高了基于纳米材料的电子、催化、可持续能源转化与存储等元器件的性能. 纳米材料的性能随着材料形状、尺寸、以及维度的变化而改变, 因此, 纳米材料的合成与设计在合理使用与进一步提高现有纳米材料技术与功能材料性能上是至关重要的一步. 本综述总结概述了不同维度金属氧化物纳米材料, 尤其是以应用最为广泛的氧化钛、氧化锌和氧化锡为代表的纳米材料比较通行的合成方法与策略. 此外归纳了各类合成方法以及实验方案并分析了各方法中存在的优缺点. 通过对现行合成策略的纵览和理解, 我们期待能够进一步发展和优化出以性能为导向的纳米结构并进一步推动纳米科学和技术的发展与进步.

Basal-plane slip systems and polymorphic phase transformation in Ti2AlC and Ti2AlN: a first-principles study

Deformation modes are studied for two basal-plane slip systems, [1 (2) over bar 10](0001) and [(1) over bar 010](0001), in ternary-layered Ti2AlC and Ti2AlN ceramics using the first-principles plane-wave pseudopotential total energy method. Based on the theoretical stress-strain curves, the [(1) over bar 010](0001) slip system leads to smaller ideal shear strength compared to the [1 (2) over bar 10](0001) mode, implying that the [(1) over bar 010]( 0001) slip system is predominant to the mechanical properties of these ternary-layered compounds. Bond-length relaxations are examined for materials strained from elasticity to structural instability. Interatomic bonds are demonstrated to respond to shear strain inhomogeneously because of different bonding strengths. The slips of atomic planes are determined by the failure of weak Ti-Al bonds. In addition, we predict a polymorphic phase transformation along the [1 (2) over bar 10](0001) shear deformation path. For the [(1) over bar 010](0001) slip system, in contrast, no polymorphic phase transformation is observed because TiC slabs do not hold the original NaCl-type structure and, in addition, Al layers change from a hexagonal to a cubic stacking in the shear deformed lattice. In other words, the structural units undergo different atomic configurations from those in the two polymorphs under applied shear strain.