Yuanyuan Qu

Germanium sulfide nanosheet: a universal anode material for alkali metal ion batteries

As the most promising energy storage system (ESS), rechargeable alkali-metal (AM) ion batteries have been attracting great attention. A suitable anode material is quite crucial for successful development of AM ion batteries. Using first-principles calculations, we propose that a two-dimensional (2D) group-IV monochalcogenide, germanium sulfide nanosheet (GSNS), can serve as high-performance anodes for the AM (AM = Li, Na, and K) ion batteries. The interaction between AM atoms and GSNS is strong enough to prevent the clustering of the intercalated AM atoms that may occur in other 2D materials. The low energy barriers for the diffusion of AM atoms on GSNS, 0.236 (Li), 0.090 (Na) and 0.050 eV (K), suggest the high charge/discharge rate of the GSNS anodes. Low average electrode potentials and a high AM storage capacity up to 512 mA h g−1 (for Na) can be achieved in the AM/GSNS systems. In view of the higher abundance of Na and K than that of Li, our work offers a promising anode material for the development of low-cost Na and K ion batteries with high performance.

Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation.

Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

Strain-Modulated Electronic Structure and Infrared Light Adsorption in Palladium Diselenide Monolayer.

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit intriguing properties for both fundamental research and potential application in fields ranging from electronic devices to catalysis. Based on first-principles calculations, we proposed a stable form of palladium diselenide (PdSe2) monolayer that can be synthesized by selenizing Pd(111) surface. It has a moderate band gap of about 1.10 eV, a small in-plane stiffness, and electron mobility larger than that of monolayer black phosphorus by more than one order. Additionally, tensile strain can modulate the band gap of PdSe2 monolayer and consequently enhance the infrared light adsorption ability. These interesting properties are quite promising for application in electronic and optoelectronic devices.

Efficient hydrogen isotopologues separation through a tunable potential barrier: The case of a C 2 N membrane

Isotopes separation through quantum sieving effect of membranes is quite promising for industrial applications. For the light hydrogen isotopologues (eg. H2, D2), the confinement of potential wells in porous membranes to isotopologues was commonly regarded to be crucial for highly efficient separation ability. Here, we demonstrate from first-principles that a potential barrier is also favorable for efficient hydrogen isotopologues separation. Taking an already-synthesized two-dimensional carbon nitride (C2N-h2D) as an example, we predict that the competition between quantum tunneling and zero-point-energy (ZPE) effects regulated by the tensile strain leads to high selectivity and permeance. Both kinetic quantum sieving and equilibrium quantum sieving effects are considered. The quantum effects revealed in this work offer a prospective strategy for highly efficient hydrogen isotopologues separation.

Forming heterojunction: an effective strategy to enhance the photocatalytic efficiency of a new metal-free organic photocatalyst for water splitting

Photocatalytic water splitting is a new technology for the conversion and utilization of solar energy and has a potential prospect. One important aspect of enhancing the photocatalytic efficiency is how to improve the electron-hole separation. Up to now, there is still no ideal strategy to improve the electron-hole separation. In this article, for metal-free organic photocatalysts, we propose a good strategy- forming heterojunction, which can effectively improve the electron-hole separation. We provide a metal-free organic photocatalyst g-C12N7H3 for water splitting. The stability of g-C12N7H3 has been investigated, the X-ray diffraction spectra has been simulated. Using first-principles calculations, we have systematically studied the electronic structure, band edge alignment, and optical properties for the g-C12N7H3. The results demonstrated that g-C12N7H3 is a new organocatalyst material for water splitting. In order to enhance the photocatalytic efficiency, we provided four strategies, i.e., multilayer stacking, raising N atoms, forming g-C9N10/g-C12N7H3 heterojunction, and forming graphene/g-C12N7H3 heterojunction. Our research is expected to stimulate experimentalists to further study novel 2D metal-free organic materials as visible light photocatalysts. Our strategies, especially forming heterojunction, will substantially help to enhance the photocatalytic efficiency of metal-free organic photocatalyst.

Cu3N and its analogs: a new class of electrodes for lithium ion batteries

Electrode materials with low diffusion energy barriers and high storage capacity of lithium are crucial for high performance rechargeable lithium-ion batteries (LIBs). Based on first-principles calculations, we demonstrate a new class of electrode materials. Taking advantage of the large voids in Cu3N crystals, high lithium mobility and storage capacity can be achieved. The diffusion of Li on Cu3N nanosheets experiences an energy barrier of about 0.09 eV, which is much lower than those of presently proposed electrode materials. The maximum Li capacity of Cu3N nanosheets can reach 1008 mA h g−1. In view of a large number of crystals sharing the same lattice structure as Cu3N, this work opens an avenue for developing electrode materials for high performance LIBs.