Xingshuai Lv

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.

SnO2/Reduced Graphene Oxide Interlayer Mitigating the Shuttle Effect of Li–S Batteries

The short cycle life of lithium-sulfur batteries (LSBs) plagues its practical application. In this study, a uniform SnO2/reduced graphene oxide (denoted as SnO2/rGO) composite is successfully designed onto the commercial polypropylene separator for use of interlayer of LSBs to decrease the charge-transfer resistance and trap the soluble lithium polysulfides (LPSs). As a result, the assembled devices using the separator modified with the functional interlayer (SnO2/rGO) exhibit improved cycle performance; for instance, over 200 cycles at 1C, the discharge capacity of the cells reaches 734 mAh g-1. The cells also display high rate capability, with the average discharge capacity of 541.9 mAh g-1 at 5C. Additionally, the mechanism of anchoring behavior of the SnO2/rGO interlayer was systematically investigated using density functional theory calculations. The results demonstrate that the improved performance is related to the ability of SnO2/rGO to effectively absorb S8 cluster and LPS. The strong Li-O/Sn-S/O-S bonds and tight chemical adsorption between LPS and SnO2 mitigate the shuttle effect of LSBs. This study demonstrates that engineering the functional interlayer of metal oxide and carbon materials in LSBs may be an easy way to improve their rate capacity and cycling life.

Two-dimensional GeSe for high performance thin-film solar cells

GeSe has emerged as an appealing photovoltaic material due to the desirable electronic and optical properties as well as being an earth-abundant constituent element. We systematically explore for the first time the contact properties of bilayer GeSe with commonly used back electrode metals in detail, such as the geometric features, electronic properties, Schottky barrier, tunneling barrier, and band alignment. Our results reveal that the metals investigated, especially Au, Pt, and Ni, show great potential in forming favorable contacts with GeSe due to a low Schottky barrier and tunneling barrier. More importantly, we find that when a SnS monolayer is superimposed with GeSe layers, the combined system can be used as an effective solar cell material with type-II heterostructure alignment. The power conversion efficiency is predicted to be as high as ∼18%, which is comparable or even higher than that of previously reported solar cells. Our results not only provide microscopic insights into the characteristics between layered GeSe and metals, but also pave the way for further experimental improvements of GeSe thin-film solar cells.

Self-assembled supramolecular system PDINH on TiO 2 surface enhances hydrogen production

Constructing organic-inorganic hybrids is one of the hopeful strategies to improve photocatalyst performance. In this study, perylene-3,4,9,10-tetracarboxylic diimide (PDINH) and commercial TiO2 P25 are chosen as raw materials to construct a PDINH/TiO2 organic-inorganic hybrid, which has higher photocatalytic H2 production activity and photocurrent intensity than pure PDINH and TiO2, respectively. The apparent quantum efficiency for H2 production over 0.5%PDINH/TiO2 reaches as high as 70.69% using irradiation at 365 nm. Moreover, XRD, DRS, HRTEM, FT-IR, and XPS are used to characterize the crystal structure, optical absorption, morphology, molecular structure, and chemical bonds, as well as the elemental and chemical states of PDINH/TiO2 organic-inorganic hybrid. The interfaces between PDINH and TiO2, which largely determine photocatalytic performance, is also analyzed systematically. Furthermore, charge density difference (Δρ) is used to analyze the electron-ion interactions of PDINH and TiO2, and reveals that substantial charge transfer occurs from PDINH to TiO2.

Group IV Monochalcogenides MX (M=Ge, Sn; X=S, Se) as Chemical Anchors of Polysulfides for Lithium-Sulfur Batteries

Although rechargeable lithium-sulfur batteries are considered as advanced energy systems, their practical implementation is impeded by many factors, in particular the rapid capacity fade and low Coulomb efficiency caused by the shuttle effect. To overcome this problem for achieving longer cycle life and higher rate performance, anchoring materials for lithium polysulfides are highly desirable. In this work, for the first time, we report phosphorene-like MX (M=Ge, Sn; X=S, Se) monolayers as promising anchoring materials to restrain the lithium polysulfides shuttling. Our study provides fundamental selection criteria for the effective suppression of the polysulfides shuttling. Adsorption calculations reveal that polysulfide capture by the MX is through chemisorption with a suitable range of adsorption energies. Morever, we show that excellent surface diffusion of Li and polysulfides endow a fast charge/discharge rate for lithium-sulfur batteries. Graphene with desirable electronic properties is constructed to improve the electrical conductivity in the new graphene@MX heterostructures. Based on the strong anchoring ability, improved rate capability, and enhanced conductivity, MX-based composites hold great promise as an anchoring material for high-energy lithium-sulfur batteries.