ZnCdO2 monolayer - A complex 2D structure of ZnO and CdO monolayers for photocatalytic water splitting driven by visible-light.

ZnO monolayer possesses band structure matching the conditions of water splitting for hydrogen generation but cannot well response to the visible light, while CdO one, contrariwise, have obvious optical absorption in the visible light range but no satisfactory band edges for the water splitting to produce hydrogen. Here, we predict a two-dimensional ZnCdO2 structure comprising of ZnO and CdO ones to achieve their strengths. The band structures, optical properties, carrier mobility, and the strain engineering for ZnCdO2, ZnO and CdO monolayers are investigated by using the first-principles hybridization functional calculations. The results demonstrate that the two-dimensional ZnCdO2 structure is a promising candidate for water splitting to produce hydrogen. All the structures show a direct band energy gap and the character remains unchanged under the considered biaxial strains. All the conduction band minimums are suitable for water splitting reaction even under the -4% to +4% strain. Moreover, the valence band maximum of ZnCdO2 monolayer matches the conditions of the water-splitting reaction under the -2% to +4% strain. Interestingly, the unsatisfactory valence band maximum of CdO monolayer can be overcome by strain larger than +2%. As expected, the enhanced optical absorption in the visible light range is observed for the ZnCdO2 monolayer. Additionally, the mobilities of the hole and the electron are significantly different for the three monolayers, implying that the low recombination ratio of the photogenerated carrier pairs is available, which is also beneficial for the photocatalytic performance. Therefore, ZnCdO2 monolayer and CdO monolayer (with tensile strain larger than 2%) is a promising candidate for the water splitting to produce hydrogen under the irradiation of the solar light.

Photocatalytic hydrogen production from water splitting with N-doped ß-Ga2O3 and visible light.

Based on the first principles calculations, the feasibility of the photocatalytic hydrogen production from water splitting driven by N-doped ß-Ga2O3 in the visible light is investigated. The formation energy and dynamics properties are used to examine the stability of the doped structures. The absolute positions of the band energy edges are obtained and compared to the redox potentials of the hydrogen production reaction. Moreover, we calculate the carrier lifetime and mobility for both electron and hole of all the considered structures. The optical absorption is also calculated for each structure. The results show that the 5.00 at.% N-doped ß-Ga2O3 has the satisfactory band energy edges, obvious difference of mobilities between electron and hole, and significant enhancement of absorption in visible light range, indicating it is a promising photocatalytic material to catalyze hydrogen production from water splitting under the irradiation of the visible light.

Globally Accurate Potential Energy Surface for HCS(A2A″) by Extrapolation to the Complete Basis Set Limit.

A global potential energy surface (PES) representation of the C(3P) + SH(X 2Π) → H(2S) + CS(a 3Π) system is developed by fitting plenty of precise energies obtained through the ab initio calculation with aug-cc-pV QZ and aug-cc-pV5Z basis sets via extrapolation to the complete basis set limit. The topographical characteristics of the PES are examined in detail, and it is found that they agree well with previous calculations available in the literature. By utilizing the PES of HCS(A2A″), the corresponding reaction is investigated using the quasi-classical trajectory (QCT) method in the collision energy range of 0.08-1.0 eV. The minimum energy paths (MEPs) calculated on the basis of the present PES indicate that the C(3P) + SH(X 2Π) → H(2S) + CS(a 3Π) reaction is exothermic, with the exothermicity ∼0.204 eV. The calculation for the capture time indicates that the reaction is mainly governed by the indirect mechanism at the lower collision energy, while, for higher collision energy, the direct mechanism is in coexistence with the indirect mechanism, and the latter one plays a dominant role.

Globally accurate potential energy surface for the ground-state HCS(X2A') and its use in reaction dynamics.

A globally accurate many-body expansion potential energy surface is reported for HCS(X2A') by fitting a wealth of accurate ab initio energies calculated at the multireference configuration interaction level using aug-cc-pVQZ and aug-cc-pV5Z basis sets via extrapolation to the complete basis set limit. The topographical features of the present potential energy surface are examined in detail and is in good agreement with the raw ab initio results, as well as other theoretical results available in literatures. By utilizing the potential energy surface of HCS(X2A'), the dynamic studies of the C(3P) + SH(X2Π) → H(2S) + CS(X1∑+) reaction has been carried out using quasi-classical trajectory method.

State-to-State Quantum Dynamics of Reactions O((3)P) + HD (v = 0-1, j = 0) → OH+D and OD+H: Reaction Mechanism and Vibrational Excitation.

Time-dependent quantum wave packet dynamics calculations have been performed in order to characterize the dynamics and mechanism of O((3)P) + HD (v = 0-1, j = 0) → OH+D and OD+H reactive collisions using the adiabatic potential energy surface by Rogers et al. [J. Phys. Chem. A 2000, 104, 2308] Special attention has been paid to the calculations and discussion of the state resolved integral and differential cross sections and the product state distributions. In addition, the intramolecular isotopic branching ratio has been determined. The results revealed that the OD + H is the favored product channel and the product OH has the same quantum number v as the reactant HD. For low collision energy, the product angular distributions concentrate in the backward region being consistent with a rebounding mechanism. In the case of higher collision energy, the stripping collisions with larger impact parameters tend to produce sideways and forward scatterings, especially for the HD vibrationally excited state. The cross section and intramolecular isotopic branching ratio are in agreement with the previous theoretical results. A cartoon depiction collision model is built and works well for our calculation results.