Previous investigations [H. L. Zhuang and R. G. Hennig, J. Phys. Chem. C, 2013, 117, 20440-20445; J. Kang, S. Tongay, J. Zhou, J. Li and J. Wu, Appl. Phys. Lett., 2013, 102, 012111] demonstrated that molybdenum disulfide (MoS2) is a potential photocatalyst for water splitting. However, the photogenerated electron-hole pairs in MoS2 remain in the same spatial regions, resulting in a high rate of recombination. Using first-principles calculations, we designed a MoS2-based heterostructure by stacking MoS2 on two-dimensional zinc oxide (ZnO) and investigated its structural, electronic, and optical properties. The interaction at the MoS2/ZnO interface was found to be dominated by van der Waals (vdW) forces. The energy levels of both water oxidation and reduction lie within the bandgap of the MoS2/ZnO vdW heterostructure, which guarantee their occurrence for water splitting. Moreover, a type-II band alignment and a large built-in electric field are formed at the MoS2/ZnO interface, which ensure the enhanced separation of the photogenerated electron-hole pairs. In addition, strong optical absorption in the visible region was also found in the MoS2/ZnO vdW heterostructure, indicating that it has potential for application in photovoltaic and photocatalytic devices.

Most reported carbonaceous anodes of potassium‐ion batteries (PIBs) have limited capacities. One approach to improve the performance of carbon anodes is edge‐nitrogen doping, which effectively enhances the K‐ion adsorption energy. It remains challenging to achieve high edge‐nitrogen doping due to the difficulty in controlling the nitrogen dopant configuration. Herein, a new synthesis strategy is proposed to prepare carbon anodes with ultrahigh edge‐nitrogen doping for high‐performance PIBs. Specifically, self‐assembled supermolecule precursors derived from pyromellitic acid and melamine are directly pyrolyzed. During the pyrolysis process, the amidation and imidization reactions between pyromellitic acid and melamine before carbonization enable the successful carbonization of pyromellitic acid–melamine supermolecule. The obtained 3D nitrogen‐doped turbostratic carbon (3D‐NTC) possesses a 3D framework composed of carbon nanosheets, turbostratic crystalline structure, and an ultrahigh edge‐nitrogen‐doping level up to 16.8 at% (73.7% of total 22.8 at% nitrogen doping). These features endow 3D‐NTCs with remarkable performances as PIB anodes. The 3D‐NTC anode displays a high capacity of 473 mAh g−1, robust rate capability, and a long cycle life of 500 cycles with a high capacity retention of 93.1%. This new strategy will boost the development of carbon anodes for rechargeable alkali‐metal‐ion batteries.

The structural, electronic, and optical properties of heterostructures formed by transition metal dichalcogenides MX2 (M = Mo, W; X = S, Se) and graphene-like zinc oxide (ZnO) were investigated using first-principles calculations. The interlayer interaction in all heterostructures was characterized by van der Waals forces. Type-II band alignment occurs at the MoS2/ZnO and WS2/ZnO interfaces, together with the large built-in electric field across the interface, suggesting effective photogenerated-charge separation. Meanwhile, type-I band alignment occurs at the MoSe2/ZnO and WSe2/ZnO interfaces. Moreover, all heterostructures exhibit excellent optical absorption in the visible and infrared regions, which is vital for optical applications.

Recently, a new two-dimensional allotrope of carbon (biphenylene) was experimentally synthesized. Using first-principles calculations, we systematically investigated the structural, mechanical, electronic, and HER properties of biphenylene. A large cohesive energy, absence of imaginary phonon frequencies, and an ultrahigh melting point up to 4500 K demonstrate its high stability. Biphenylene exhibits a maximum Young’s modulus of 259.7 N/m, manifesting its robust mechanical performance. Furthermore, biphenylene was found to be metallic with a n-type Dirac cone, and it exhibited improved HER performance over that of graphene. Our findings suggest that biphenylene is a promising material with potential applications in many important fields, such as chemical catalysis.

Our investigations revealed that the structural imperfection greatly influences the electronic properties of G/WSe2 vdW heterostructures.

Herein, we report a comprehensive study on the structural and electronic properties of bulk, monolayer, and multilayer PdSe 2 sheets. First, we present a benchmark study on the structural properties of bulk PdSe 2 by using 13 commonly used density functional theory (DFT) functionals. Unexpectedly, the most commonly used van der Waals (vdW)-correction methods, including DFT-D2, optB88, and vdW-DF2, fail to provide accurate predictions of lattice parameters compared to experimental data (relative error > 15%). On the other hand, the PBE-TS series functionals provide significantly improved prediction with a relative error of <2%. Unlike hexagonal two-dimensional materials like graphene, transition metal dichalcogenides, and h-BN, the conduction band minimum of monolayer PdSe 2 is not located along the high symmetry lines in the first Brillouin zone; this highlights the importance of the structure–property relationship in the pentagonal lattice. Interestingly, high valley convergence is found in the conduction and valence bands in monolayer, bilayer, and trilayer PdSe 2 sheets, suggesting promising application in thermoelectric cooling.

No abstract

Both anisotropic and Janus two-dimensional materials are known for extraordinary properties. We predict a two-dimensional material, B2P6, which combines anisotropy with the Janus geometry, based on evolutionary search and first-principles calculations. High stability of the material is demonstrated in terms of the cohesive energy, phonon spectrum, and melting point. B2P6 turns out to be an indirect band gap semiconductor with anisotropic electronic transport and strong absorption of solar radiation. Importantly, its Janus structure results in an intrinsic electric field, which significantly suppresses the recombination of photogenerated carriers. We demonstrate high efficiency of photocatalytic water splitting with a solar-to-hydrogen efficiency of 28.2%, by far in excess of the conventional theoretical limit of 18%. The structural anisotropy is found to be promising for application in metal-ion batteries. We observe directional diffusion with Li, Na, and K diffusion barriers of only 0.07, 0.04, and 0.03 eV, respectively, suggesting ultrafast charge/discharge characteristics.