Qilong Sun

Chemical Adsorption Enhanced CO2 Capture and Photoreduction over a Copper Porphyrin Based Metal Organic Framework

Effective CO2 capture and activation is a prerequisite step for highly efficient CO2 reduction. In this study, we reported a case of Cu(2+) in a porphyrin based MOF promoted enhanced photocatalytic CO2 conversion to methanol. Compared with the sample without Cu(2+), the methanol evolution rate was improved as high as 7 times. In situ FT-IR results suggested that CO2 chemical adsorption and activation over Cu(2+) played an important role in improving the conversion efficiency.

Ab Initio Prediction and Characterization of Mo2C Monolayer as Anodes for Lithium-Ion and Sodium-Ion Batteries

Identifying suitable electrodes materials with desirable electrochemical properties is urgently needed for the next generation of renewable energy technologies. Here we report an ideal candidate material, Mo2C monolayer, with not only required large capacity but also high stability and mobility by means of first-principles calculations. After ensuring its dynamical and thermal stabilities, various low energy Li and Na adsorption sites are identified, and the electric conductivity of the host material is also maintained. The calculated minor diffusion barriers imply a high mobility and cycling ability of Mo2C. In addition, the Li-adsorbed Mo2C monolayer possesses a high theoretical capacity of 526 mAh·g(-1) and a low average electrode potential of 0.14 eV. Besides, we find that the relatively low capability of Na-adsorbed Mo2C (132 mAh·g(-1)) arises from the proposed competition mechanism. These results highlight the promise of Mo2C monolayer as an appealing anode material for both lithium-ion and sodium-ion batteries.

A Bismuth‐Based Metal–Organic Framework as an Efficient Visible‐Light‐Driven Photocatalyst

A visible-light-responsive bismuth-based metal-organic framework (Bi-mna) is demonstrated to show good photoelectric and photocatalytic properties. Combining experimental and theoretical results, a ligand-to-ligand charge transfer (LLCT) process is found to be responsible for the high performance, which gives rise to a longer lifetime of photogenerated charge carriers. Our results suggest that bismuth-based MOFs could be promising candidates for the development of efficient visible-light photocatalysts.

Design of lateral heterostructure from arsenene and antimonene

Lateral heterostructures fabricated by two-dimensional building blocks have opened up exciting realms in material science and device physics. Identifying suitable materials for creating such heterostructures is urgently needed for the next-generation devices. Here, we demonstrate a novel type of seamless lateral heterostructures with excellent stabilities formed within pristine arsenene and antimonene. We find that these heterostructures could possess direct and reduced energy gaps without any modulations. Moreover, the highly coveted type-II alignment and the high carrier mobility are also identified, marking the enhanced quantum efficiency. The tensile strain can result in efficient bandgap engineering. Besides, the proposed critical condition for favored direct energy gaps would have a guiding significance on the subsequent works. Generally, our predictions not only introduce new vitality into lateral heterostructures, enriching available candidate materials in this field, but also highlight the potential of these lateral heterostructures as appealing materials for future devices.

Lateral heterojunctions within monolayer h-BN/graphene: a first-principles study

Very recently, the lateral heterojunctions of hexagonal boron nitride (h-BN)/graphene were experimentally realized for the time. To study the related properties of such heterojunctions with the purpose of searching for new avenues to realize controllable and tunable 2D electric devices, in the present work we perform a systematic theoretical investigation on a series of structures constructed by zigzag h-BN and zigzag graphene monolayers based on first-principles calculations. Our results demonstrate that the electronic structures as well as the magnetic properties of the hybridized monolayers can be modified efficiently. Furthermore, the character transition from insulator to metal can also be realized by the proposed approaches of adjusting the numbers or the ratios of the zigzag h-BN and zigzag graphene. Interestingly, the investigation of the strain dependence of the electronic properties in the selected structure reveals that the external strain applied along the Y-axis plays a decisive role in the bandgap engineering. Moreover, the calculated effective masses give a reasonable physical representation of the carrier transport properties. Our results show that the mobility direction of the charge carriers is parallel to the interface. These predictions provide new potential strategies for tuning electronic properties and will allow new device functionalities, such as in-plane transistors, diodes and spintronic devices, to be integrated within a single thin layer.

Two-dimensional metalloporphyrin monolayers with intriguing electronic and spintronic properties

Recently, intensive efforts have been focused on the search of novel two-dimensional (2D) materials for memory and spintronic applications. In the present work, we provide a practical avenue for achieving the long-cherished nanomaterial via novel 2D periodic metalloporphyrin frameworks (referred to as M-Pp0 and M-Pp45, M = Cr, Mn, Fe, Co, Ni, Cu and Zn) with regularly and separately distributed transition-metals (TMs) by means of first-principles calculations combined with Monte Carlo simulations. The electronic and magnetic properties of these novel 2D systems are systematically investigated. Our results reveal that Ni-Pp0 and Zn-Pp0 are nonmagnetic, while Cr-Pp0, Fe-Pp0 and Cu-Pp0 are weak antiferromagnetic and Co-Pp0 is paramagnetic. For M-Pp45 frameworks, however, the spin couplings are all identified to be paramagnetic arising from their long spin coherence length. Remarkably, the introduced TMs have tremendous influence on the band gap of the M-Pp45 frameworks. What is more interesting is that the Mn-Pp0 framework exhibits long-range ferromagnetic spin coupling as well as half-metallic nature. By performing Monte Carlo simulations based on the Ising model, we further demonstrate that the Mn-Pp0 framework would possess a Curie temperature (TC) of 320 K, suggesting a real sense of room temperature is achieved. These results would shed light on future experimental researches on spintronics.

Vertical and Bidirectional Heterostructures from Graphyne and MSe2 (M = Mo, W).

Vertical and lateral heterostructures with atomically clean and sharp interfaces have opened up new realms in materials science, device physics and engineering. Herein, inspired by recent experiments, the unprecedented bidirectional heterostructures (BDHs) of γ-graphyne@MoSe2/WSe2 as well as γ-graphyne@MoSe2 and γ-graphyne@WSe2 are proposed and examined on the basis of first-principles calculations. Our results reveal that a novel wrinkled γ-graphyne with narrowed energy gap and strong binding strength is achieved on the planar and smooth substrate in γ-graphyne@MoSe2/WSe2. The direct-indirect band gap crossover is also found in terms of interlayer coupling. Furthermore, we demonstrate that electron-hole pairs can be spatially separated, and the carrier mobility would be benefited from the absorbed γ-graphyne in the BDHs. These results provide not only new insights into the physical and chemical properties of the vertical and bidirectional heterostructures, but also a new strategy for fabricating unprecedented 2D nanomaterials with exciting properties.

Sc2C as a Promising Anode Material with High Mobility and Capacity: A First-Principles Study

Two-dimensional (2D) Sc2 C, an example of a MXene, has been attracting extensive attention due to its distinctive properties and great potential in applications such as energy storage. In light of its high capacity and fast charging-discharging performance, Sc2 C exhibits significant potential as an anode material for lithium- and sodium-ion batteries. Herein, a systematic investigation of Li/Na atom adsorption and diffusion on Sc2 C planes was performed based on density functional calculations. The metallic character of pristine and adsorbed Sc2 C ensures desirable electric conductivity, which indicates the advantages of 2D Sc2 C for lithium- and sodium-ion batteries. A significant charge transfer from the Li/Na atoms to Sc2 C is predicted, which indicates the cationic state of the adatoms. In addition, the diffusion barriers are as low as 0.018 and 0.012 eV for Li and Na, respectively, which illustrates the high mobility and cycling ability of Sc2 C. In particular, each formula unit of Sc2 C can adsorb up to two Li/Na atoms, which corresponds to a relatively high theoretical capacity of 462 or 362 mAh g-1 . The average electrode potential was calculated to be as low as 0.32 and 0.24 V for stoichiometric Li2 Sc2 C and Na2 Sc2 C, respectively, which makes Sc2 C attractive for the overall voltage of the cell. Herein, our results suggest that Sc2 C could be a promising anode candidate for both lithium-ion and sodium-ion batteries.

Ideal Spintronics in Molecule-Based Novel Organometallic Nanowires

With the purpose of searching for new intriguing nanomaterial for spintronics, a series of novel metalloporphyrin nanowires (M-PPNW, M = Cr, Mn, Fe, Co, Ni, Cu and Zn) and hybrid nanowires fabricated by metalloporphyrin and metal-phthalocyanine (M-PCNW) are systematically investigated by means of first-principles calculations. Our results indicate that the transition metal atoms (TMs) embedded in the frameworks distribute regularly and separately, without any trend to form clusters, thus leading to the ideally ordered spin distribution. Except for the cases embedded with Ni and Zn, the others are spin-polarized. Remarkably, the Mn-PPNW, Mn-PCNW, MnCu-PPNW, MnCr-PCNW, and MnCu-PCNW frameworks all favor the long-ranged ferromagnetic spin ordering and display half-metallic nature, which are of greatest interest and importance for electronics and spintronics. The predicted Curie temperature for the Mn-PCNW is about 150 K. In addition, it is found that the discrepancy in magnetic coupling for these materials is related to the competition mechanisms of through-bond and through-space exchange interactions. In the present work, we propose not only two novel sets of 1D frameworks with appealing magnetic properties, but also a new strategy in obtaining the half-metallic materials by the combination of different neighboring TMs.

In-plane heterostructures of Sb/Bi with high carrier mobility

In-plane two-dimensional (2D) heterostructures have been attracting public attention due to their distinctive properties. However, the pristine materials that can form in-plane heterostructures are reported only for graphene, hexagonal BN, transition-metal dichalcogenides. It will be of great significance to explore more suitable 2D materials for constructing such ingenious heterostructures. Here, we demonstrate two types of novel seamless in-plane heterostructures combined by pristine Sb and Bi monolayers by means of first-principle approach based on density functional theory. Our results indicate that external strain can serve as an effective strategy for bandgap engineering, and the transition from semiconductor to metal occurs when a compressive strain of -8% is applied. In addition, the designed heterostructures possess direct band gaps with high carrier mobility (∼4000 cm2 V-1 s-1). And the mobility of electrons and holes have huge disparity along the direction perpendicular to the interface of Sb/Bi in-plane heterostructures. It is favorable for carriers to separate spatially. Finally, we find that the band edge positions of Sb/Bi in-plane heterostructures can meet the reduction potential of hydrogen generation in photocatalysis. Our results not only offer alternative materials to construct versatile in-plane heterostructures, but also highlight the applications of 2D in-plane heterostructures in diverse nanodevices and photocatalysis.