Dramatically Enhanced Visible Light Response of Monolayer ZrS2 via Non-covalent Modification by Double-Ring Tubular B20 Cluster

First-principles study on the electronic structure and photocatalytic property of a novel two-dimensional ZrS2/InSe heterojunction

Photocatalytic water cracking technology provides a broad prospect for solving the current energy crisis using solar energy and water resources. In this paper, a two-dimensional ZrS2/InSe heterojunction for accelerating the process of hydrogen production from water decomposition was constructed, and its electronic structure and photocatalytic property were studied using first-principles calculation. The results show that the lattice mismatch rate of the heterojunction from monolayer ZrS2 and monolayer InSe is 2.48%, and its binding energy is -1.696 eV, indicating that the structure of the heterojunction is stable. The ZrS2/InSe heterojunction is an indirect bandgap with a bandgap value of 1.41 eV and a typical type-II band arrangement. Importantly, the ZrS2/InSe heterostructure has a Z-scheme structure, which is beneficial to the separation of photogenerated electron hole pairs. Moreover, the ZrS2/InSe heterojunction has a strong absorption ability for visible light (up to 3.84 × 105 cm-1), which is helpful for improving its photocatalytic efficiency. The two-dimensional ZrS2/InSe heterojunction is a very promising photocatalyst, as concluded from the above studies.

Penta-Graphene as a Potential Gas Sensor for NOx Detection

Two-dimensional (2D) penta-graphene (PG) with unique properties that can even outperform graphene is attracting extensive attention because of its promising application in nanoelectronics. Herein, we investigate the electronic and transport properties of monolayer PG with typical small gas molecules, such as CO, CO2, NH3, NO and NO2, to explore the sensing capabilities of this monolayer by using first-principles and non-equilibrium Green's function (NEGF) calculations. The optimal position and mode of adsorbed molecules are determined, and the important role of charge transfer in adsorption stability and the influence of chemical bond formation on the electronic structure of the adsorption system are explored. It is demonstrated that monolayer PG is most preferred for the NOx (x = 1, 2) molecules with suitable adsorption strength and apparent charge transfer. Moreover, the current-voltage (I-V) curves of PG display a tremendous reduction of 88% (90%) in current after NO2 (NO) adsorption. The superior sensing performance of PG rivals or even surpasses that of other 2D materials such as graphene and phosphorene. Such ultrahigh sensitivity and selectivity to nitrogen oxides make PG a superior gas sensor that promises wide-ranging applications.

Ultrahigh power factors in P-type 1T-ZrX2 (X = S, Se) single layers

The thermoelectric performances of 1T-ZrX₂ (X = S and Se) single layers were investigated using a combination of density functional calculations and semi-classical Boltzmann transport theory. Because of the high hole mobilities at 300 K, ultrahigh power factors (PF=S²σ) were found in the P-type compounds; these values were ∼ 11.95 and ∼13.58 mW K^-2 m^-1 for 1T-ZrS₂ and 1T-ZrSe₂ single layers, respectively. However, because of the Lorenz relation between the electrical conductivity (σ) and an electron's thermal conductivity (κ_el) given by the Wiedemann-Franz law, the electronic figures of merit (Z_elT=PF·T/κ_el) at 300 K were approximately 0.67 and 0.75 for the N- and P-type 1T-ZrSe₂, respectively. In addition, the lattice thermal conductivities (κ_ph) were calculated, giving values of ∼1.43 and ∼0.97 W K^-1 m^-1 for 1T-ZrS₂ and 1T-ZrSe₂ single layers, respectively. Therefore, because of the lower κ_ph/κ_el ratio, the P-type 1T-ZrX₂ single layers possess higher figure-of-merits (ZT=Z_elT/1+κ_phκ_el) than their counterparts. This signifies that the P-type samples demonstrate better thermoelectric performance than the N-type ones. The thermoelectric properties of metastable 2H-ZrX₂ (X = S and Se) single layers were also investigated.