Theoretical Study on the Dehydrogenation Reaction of H_2S by VS^+ (~3Σ^-)

The dehydrogenation reaction of H2S by the ^3Σ^- ground state of VS^＋： VS^＋ ＋ H2S → VS2^＋ ＋ H2 has been studied by using Density Functional Theory （DPT） at the B3LYP/DZVP level. It is found that the reaction proceeds along two possible pathways （A and B） yielding two isomer dehydrogenation products VS2^＋-1 （^3B2） and VS2^＋-2 （^3A1）, respectively. For both pathways, the reaction has a two-step-reaction mechanism that involves the migration of two hydrogen atoms from S2 to V^＋, respectively. The migration of the second hydrogen via TS3 and that of the first via TS4 are the rate-determining steps for pathways A and B, respectively. The activation energy is 17.4 kcal/mol for pathway A and 22.8 kcal/mol for pathway B relative to the reactants. The calculated reaction heat of 9.9 kcal/mol indicates the endothermicity of pathway A and that of -11.9 kcal/mol suggests the exothermicity of pathway B.

High-capacity lithium-rich cathode oxides with multivalent cationic and anionic redox reactions for lithium ion batteries

Lithium-rich cathode oxides with capability to realize multivalent cationic and anionic redox reactions have attracted much attention as promising candidate electrode materials for high energy density lithium ion batteries because of their ultrahigh specific capacity. However, redox reaction mechanisms, especially for the anionic redox reaction of these materials, are still not very clear. Meanwhile, several pivotal challenges associated with the redox reactions mechanisms, such as structural instability and limited cycle life, hinder the practical applications of these high-capacity lithium-rich cathode oxides. Herein, we review the lithium-rich oxides with various crystal structures. The multivalent cationic/anionic redox reaction mechanisms of several representative high capacity lithium-rich cathode oxides are discussed, attempting to understand the origins of the high lithium storage capacities of these materials. In addition, we provide perspectives for the further development of these lithium-rich cathode oxides based on multivalent cationic and anionic redox reactions, focusing on addressing the fundamental problems and promoting their practical applications.

Synthesis of halide perovskite microwires via methylammonium cations reaction

Low-dimensional halide perovskites(HPs)have received considerable attention in recent years due to their novel physical properties such as compositional flexibility,high quantum yield,quantum size effects and superior charge transport.Here we show room temperature solution synthesis of 1D organic-inorganic lead bromide perovskite microwires(MWs).Our method uses acetone as a reactant,and when CH3NH3PbBr3 is immersed,acetone reacts with CH3NH3+cations in the CH3NH3PbBr3 single crystal by the dehydration condensation.The reaction generates a large(CH3)2C=NHCH3+A-site which cannot be accommodated by the cuboctahedron formed by the corner-sharing[PbBr6]4−octahedral,leading to the transition of corner-sharing octahedra to face-sharing triangular prism and the crystal structure transformation from 3D to 1D.The formation process of(CH3)2C=NHCH3PbBr3 MWs does not involve any ligands,templates or catalysts.A two-terminal memory device was constructed using the(CH3)2C=NHCH3PbBr3 MWs,showing great potential of the method in fabrication of electronic and optoelectronic devices.

Telluride semiconductor nanocrystals:progress on their liquid-phase synthesis and applications

The synthesis of colloidal telluride semiconductor nanocrystals(CT-SNCs)is more challenging than that of chalcogenides,due to the smaller electron affinity of tellurium than that of sulfur and selenium,which is attributed to its metalloid property.While some new potential strategies were developing with the increasing demand of CT-SNCs,the cation exchange reaction(CER)has particularly become a new strategy to synthesize highquality CT-SNCs and their corresponded hetero-nanostructures.This review summarizes the synthesis strategies of CT-SNCs,including traditional methods and new methods with emphasis on CERs,and their resulting CTSNCs with well-controlling size,shape,composition,crystallization and hetero-interfaces cooperatively.The progressive synthesis methods give rise to the excellent optical properties of CT-SNCs.This review also covers the recent progress of their applications in the field of photoelectric detection,catalysis,batteries and biology.The new hybrid CT-SNCs nanostructures are also emphasized and systematically discussed due to their enhanced properties.