Zhaoshun Meng

Efficient band structure tuning, charge separation, and visible-light response in ZrS2-based van der Waals heterostructures

As a fast emerging topic, van der Waals heterostructures can modify two-dimensional (2D) layered materials with desired properties, thus greatly extending the applications of these materials. Via state-of-the-art first-principles calculations, we systematically study four types of van der Waals heterostructures formed by monolayer graphene, h-BN, g-C3N4, and polyphenylene on ZrS2 nanosheets. A direct band gap can be obtained in the graphene/ZrS2 heterostructure, endowing graphene with the real ability to be applied in nanoelectronics, whereas the van der Waals interactions of graphene significantly broadens the optical absorption of ZrS2. The conduction band and valence band of the four heterostructures are contributed by the ZrS2 layer and the other layer, respectively, meaning good charge separation is achieved. We proposed that the strained h-BN/ZrS2 and g-C3N4/ZrS2 heterostructures satisfy fundamental aspects for photocatalytic water splitting, with the reduction and oxidation levels well inside their band gaps. By forming heterostructures with ZrS2, the optical properties of h-BN, g-C3N4 and polyphenylene show a remarkable improvement in the visible-light region. The findings in this study will be of broad interest in van der Waals heterostructure research and in the photocatalysis field.

Ultrahigh energy storage and ultrafast ion diffusion in borophene-based anodes for rechargeable metal ion batteries

Since the turn of the new century, the increasing demand for high-performance energy storage systems has generated considerable interest in rechargeable ion batteries (IBs). However, current IB technologies are not entirely satisfactory, especially the electrodes. We report here, via density functional theory calculations and first principles molecular dynamics simulations, that a borophene anode material has the fascinating properties of ultrahigh energy storage and ultrafast ion diffusion in metal (Li, Na, K, Mg, Al) IBs. Particularly for Li IBs with a borophene anode, a specific density of 3306 mA h g−1 and a high charging voltage of 1.46 V can be maintained at room temperature. Furthermore, non-ideal borophene anodes, including those with defects or oxidation and nanoribbon samples, still possess good properties for practical applications. This theoretical exploration will provide helpful guidance in searching for available or novel boron nanosheets as promising anode materials to advance commercial IB technology.

Lithium decoration of three dimensional boron-doped graphene frameworks for high-capacity hydrogen storage

Based on density functional theory and the first principles molecular dynamics simulations, a three-dimensional B-doped graphene-interconnected framework has been constructed that shows good thermal stability even after metal loading. The average binding energy of adsorbed Li atoms on the proposed material (2.64 eV) is considerably larger than the cohesive energy per atom of bulk Li metal (1.60 eV). This value is ideal for atomically dispersed Li doping in experiments. From grand canonical Monte Carlo simulations, high hydrogen storage capacities of 5.9 wt% and 52.6 g/L in the Li-decorated material are attained at 298 K and 100 bars.

Graphdiyne as a High-Efficiency Membrane for Separating Oxygen from Harmful Gases: A First-Principles Study

We theoretically explored the adsorption and diffusion properties of oxygen and several harmful gases penetrating the graphdiyne monolayer. According to our first-principles calculations, the oxidation of the acetylenic bond in graphdiyne needs to surmount an energy barrier of ca. 1.97 eV, implying that graphdiyne remains unaffected under oxygen-rich conditions. In a broad temperature range, graphdiyne with well-defined nanosized pores exhibits a perfect performance for oxygen separation from typical noxious gases, which should be of great potential in medical treatment and industry.

Influences of lithium doping and fullerene impregnation on hydrogen storage in metal organic frameworks

Using the grand canonical ensemble Monte Carlo method, two similar metal organic frameworks (isoreticular MOFs [IRMOF]-12 and -14) and their modified structures by doping lithium (Li) atoms above the organic units and/or impregnating with fullerenes in their cavities have been employed to investigate the capacities of H2 storage. Our simulations show that the H2 uptakes of Li-C60@Li-IRMOF-12 and Li-C60@Li-IRMOF-14 achieve the U.S. Department of Energy targets before 2017 both in gravimetric density and in volumetric density at 243 K and 100 bar. Combining the results of IRMOF-10-based structures, we further study the relationships between the H2 uptakes and the physical properties of the materials to identify the influence factors on the H2 storage at room temperature.

Nanoporous MoS2 monolayer as a promising membrane for purifying hydrogen and enriching methane

We present a theoretical prediction of a highly efficient membrane for hydrogen purification and natural gas upgrading, i.e. laminar MoS2 material with triangular sulfur-edged nanopores. We calculated from first principles the diffusion barriers of H2 and CO2 across monolayer MoS2 to be, respectively, 0.07 eV and 0.17 eV, which are low enough to warrant their great permeability. The permeance values for H2 and CO2 far exceed the industrially accepted standard. Meanwhile, such a porous MoS2 membrane shows excellent selectivity in terms of H2/CO, H2/N2, H2/CH4, and CO2/CH4 separation (>103, >  103, >  106, and  >  104, respectively) at room temperature. We expect that the findings in this work will expedite theoretical or experimental exploration on gas separation membranes based on transition metal dichalcogenides.