Dihua Wu

Enhanced Li Adsorption and Diffusion on MoS2 Zigzag Nanoribbons by Edge Effects: A Computational Study.

By means of density functional theory computations, we systematically investigated the adsorption and diffusion of Li on the 2-D MoS2 nanosheets and 1-D zigzag MoS2 nanoribbons (ZMoS2NRs), in comparison with MoS2 bulk. Although the Li mobility can be significantly facilitated in MoS2 nanosheets, their decreased Li binding energies make them less attractive for cathode applications. Because of the presence of unique edge states, ZMoS2NRs have a remarkably enhanced binding interaction with Li without sacrificing the Li mobility, and thus are promising as cathode materials of Li-ion batteries with a high power density and fast charge/discharge rates.

S‐Doped N‐Rich Carbon Nanosheets with Expanded Interlayer Distance as Anode Materials for Sodium‐Ion Batteries

2D composites with S doping into N-rich carbon nanosheets are fabricated, whose interlayer distance becomes large enough for Na+ insertion and diffusion. The large surface area and stable structure also provide more sites for Na+ adsorption, leading to high Na-storage capacity and excellent rate performance. Moreover, Faradaic reactions between Na+ and tightly bound S is beneficial for further improvement of Na-storage capacity.

MnPSe3 Monolayer: A Promising 2D Visible‐Light Photohydrolytic Catalyst with High Carrier Mobility

The 2D material single‐layer MnPSe3 would be a promising photocatalyst for water splitting, as indicated by the proper positions of band edges, strong absorption in visible‐light spectrum, broad applicability (pH = 0 – 7), and high carrier mobility.

A Ti-anchored Ti2CO2 monolayer (MXene) as a single-atom catalyst for CO oxidation

First-principles computations were performed to investigate the catalytic oxidation of CO on a Ti-anchored Ti2CO2 monolayer, a typical MXene. The Ti2CO2 monolayer could prevent the formation of Ti clusters. Both Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) mechanisms were considered, and the results manifest that the Ti-anchored Ti2CO2 monolayer exhibits very high activity even comparable to many noble metal catalysts for low-temperature CO oxidation. This work contributes to designing more effective and nonprecious-metal single-atom catalysts and widening the applications of MXene-based materials.

Stable layered P3/P2 Na0.66Co0.5Mn0.5O2 cathode materials for sodium-ion batteries

Rechargeable sodium-ion batteries are promising next-generation energy storage devices due to the low cost and rich natural abundance of Na. However, it is still a great challenge to suppress phase changes of cathode materials in the high-voltage region. Unlike P-type single-phase composites, herein we present a facile strategy for preparing P3/P2-type biphasic layered Na0.66Co0.5Mn0.5O2, namely, integrating P2 into P3-layered materials. The crystalline structure of Na0.66Co0.5Mn0.5O2, which was investigated by ex situ X-ray diffraction, was well maintained over long cycling in a high-voltage range. Taking advantage of their structural stabilization, Na0.66Co0.5Mn0.5O2 cathode materials displayed remarkably steady discharge capacity at high rates. With outstanding structural flexibility and electrochemical performance, Na0.66Co0.5Mn0.5O2 would stimulate the development of sodium-ion batteries.

Ti2CO2 MXene: a highly active and selective photocatalyst for CO2 reduction

Photocatalytic reduction of carbon dioxide (CO2) into hydrocarbons could promote the CO2 utilization and retard the greenhouse effect, which has gained much attention. Due to high surface–bulk ratio, two-dimensional materials can be promising candidates for catalysis. In this study, by means of first-principles computations, we have investigated the reduction of CO2 at the oxygen vacancy on MXene monolayers. Among Ti2CO2, V2CO2 and Ti3C2O2, Ti2CO2 has exhibited the best catalytic performance for the reduction of CO2. The reaction pathway CO2 → HCOO → HCOOH was found to be favorable with an energy barrier of 0.53 eV. The energy barriers of the reaction pathways for other single-carbon organic products were much higher, indicating high selectivity for HCOOH. Moreover, we have proposed that CO and H2 can introduce sufficient oxygen vacancies on O-terminated MXene. This study provides new insights into the design of catalysts for the reduction of CO2 and further widens the applications of MXene-based materials.

Designing high-voltage carbonyl-containing polycyclic aromatic hydrocarbon cathode materials for Li-ion batteries guided by Clar's theory

Increasing the voltage of organic electrodes is critical in improving their energy density. Here, we examined the correlation between the electron delocalization (aromaticity) and the lithiation voltage of carbonyl-containing polycyclic aromatic hydrocarbons by means of density functional theory computations. Our analyses revealed that the correlation can be well explained by Clars aromatic sextet theory. An index denoted as ΔC2Li is introduced to characterize the aromaticity change during lithiation. Several molecules with high ΔC2Li and high voltage were designed, and we also experimentally investigated a molecule with positive ΔC2Li as the cathode material. Our results demonstrated the importance and the feasibility of Clars theory in screening and developing high-voltage organic electrode materials.

Ab initio investigations on bulk and monolayer V2O5 as cathode materials for Li-, Na-, K- and Mg-ion batteries

First-principles computations based on density functional theory (DFT) were performed to investigate the performance of bulk and monolayer V2O5 as the cathode material for Li-, Na-, K- and Mg-ion batteries. Both the average voltage and ion migration barrier were studied. The results indicate that alkali metal ions with a large ionic radius (such as Na and K) have much lower migration barriers (0.44 and 0.39 eV for Na and K, respectively) on monolayer V2O5 than in bulk V2O5 (1.17 and 1.66 eV) without great voltage loss, while for Li polymorphs, the difference between monolayer and bulk V2O5 is minimal. However, the performance of monolayer V2O5 is not ideal enough as the cathode material for multivalent metal-ion (such as Mg) batteries. As a result, for Na- and K-ion batteries with a large ionic size, monolayer V2O5 is an attractive cathode material.

High Carrier Mobility and Pronounced Light Absorption in Methyl-Terminated Germanene: Insights from First-Principles Computations.

On the basis of Herd-Scuseria-Emzerhof hybrid functional (HSE06) within the framework of density functional theory (DFT), we have computationally explored the intrinsic electronic and optical properties of 2D methyl-terminated germanene (GeCH3). GeCH3 monolayer possesses an opportune direct band gap of 1.76 eV, which can be effectively tuned by applying elastic strain and decreases with increasing the tensile strain, while it increases with small compressive strain. Also, anisotropic carrier mobility was disclosed in the armchair (x) and zigzag (y) directions of GeCH3 monolayer. Moreover, GeCH3 monolayer shows significant light absorption in the visible and ultraviolet range of solar spectrum and is attractive for light harvesting. The results can help us better understand the intrinsic properties of GeCH3 and provide reliable guidance for its experimental applications to electronics and optoelectronics.

Structure-modulated crystalline covalent organic frameworks as high-rate cathodes for Li-ion batteries

Sustainable and resourceful organic materials are of long-standing interest for lithium-ion batteries. However, the lack of structural stability and cyclic capability is still the bottleneck for their practical use. Here, two new chemically stable naphthalimide-based crystalline covalent organic frameworks (COFs) were first synthesized through a simple solvothermal route. Excellent electrochemical performances were achieved as cathode materials for Li-ion batteries, mainly due to their open ordered nanoporous framework and robust structure. Moreover, their electrochemical performance can be improved by simply altering the linker of COFs at the molecular level. This work provides a possible approach to obtain the desired performance by structural modulation of organic materials.