Size-Dependent Reactivity of Co ( = 5-25) Cluster Anions toward Carbon Dioxide.

A fundamental understanding of the reactivity evolution of nanosized clusters at an atomically precise level is pivotal to assemble desired materials with promising candidates. Benefiting from the tandem mass spectrometer coupled with a high-temperature ion-trap reactor, the reactions of mass-selected Co ( = 5-25) clusters with CO were investigated and the increased reactivity of Co was newly discovered herein. This finding marks an important step to understand property evolution of subnanometer metal clusters (Co, ∼0.

Filtration of the preferred catalyst for reverse water-gas shift among Rh ( = 3-11) clusters by mass spectrometry under variable temperatures.

The key to optimizing energy-consuming catalytic conversions lies in acquiring a fundamental understanding of the nature of the active sites and the mechanisms of elementary steps at an atomically precise level, while it is challenging to capture the crucial step that determines the overall temperature of a real-life catalytic reaction. Herein, benefiting from a newly-developed high-temperature ion trap reactor, the reverse water-gas shift (CO + H → CO + HO) reaction catalyzed by the Rh ( = 3-11) clusters was investigated under variable temperatures (298-783 K) and the critical temperature that each elementary step (Rh + CO and RhO + H) requires to take place was identified. The Rh cluster strikingly surpasses other Rh clusters to drive the catalysis at a mild starting temperature (∼440 K).

Facile CO bond cleavage on polynuclear vanadium nitride clusters VN.

Identifying the structural configurations of precursors for CO dissociation is fundamentally interesting and industrially important in the fields of, , Fischer-Tropsch synthesis. Herein, we demonstrated that CO could be dissociated on polynuclear vanadium nitride VN clusters at room temperature, and a key intermediate, with CO in a N-assisted tilted bridge coordination where the C-O bond ruptures easily, was discovered. The reaction was characterized by mass spectrometry, photoelectron spectroscopy, and quantum-chemistry calculations, and the nature of the adsorbed CO on product VNCO was further characterized by a collision-induced dissociation experiment.

Water-Gas Shift Catalyzed by Iridium-Vanadium Oxide Clusters IrVO with Iridium in a Rare Oxidation State of -II.

The discovery of compounds containing transition metals with an unusual and well-established oxidation state is vital to enrich our horizon on formal oxidation state. Herein, benefiting from the study of the water-gas shift reaction (CO + HO → CO + H) mediated with the iridium-vanadium oxide cluster IrVO, the missing -II oxidation state of iridium was identified. The reactions were performed by using our newly developed double ion trap reactors that can spatially separate the addition of reactants and are characterized by mass spectrometry and quantum-chemical calculations.

Multiple CO reduction mediated by heteronuclear metal carbide cluster anions RhTaC.

Noble metals dispersed on transition-metal carbides exhibit extraordinary activity in CO catalytic conversion and bimetallic carbides generated at the interface were proposed to contribute to the observed activity. Heteronuclear metal carbide clusters (HMCCs) that compositionally resemble the bimetallic carbides are suitable models to get a fundamental understanding of the reactivity of the related condensed-phase catalysts, while the reaction of HMCCs with CO has not been touched in the gas phase. Herein, benefiting from the newly designed double ion trap reactors, the reaction of laser-ablation generated and mass-selected RhTaC clusters with CO was studied.

Reverse water-gas shift reaction catalyzed by diatomic rhodium anions.

The reverse water-gas shift (RWGS, CO + H → CO + HO, Δ = +0.44 eV) reaction mediated by the diatomic anion Rh was successfully constructed. The generation of a gas-phase HO molecule and ion product [Rh(CO)] was identified unambiguously at room temperature and the only elementary step that requires extra energy to complete the catalysis is the desorption of CO from [Rh(CO)].

An IrVO Cluster Catalytically Oxidizes Four CO Molecules: Importance of Ir-V Multiple Bonding.

The generation and characterization of multiple metal-metal (M-M) bonds between early and late transition metals is vital to correlate the nature of multiple M-M bonds with the related reactivity in catalysis, while the examples with multiple M-M bonds have been rarely reported. Herein, we identified that the quadruple bonding interactions were formed in a gas-phase ion IrV with a dramatically short Ir-V bond. Oxidation of four CO molecules by IrVO is a highly exothermic process driven by the generation of stable products IrV and CO, and then IrV can be oxidized by NO to regenerate IrVO.

Activation of Carbon Dioxide by CoCD ( = 0-4) Anions.

Laser ablation generated CoCD ( = 0-4) anions were mass selected and then reacted with CO in an ion trap reactor. The reactions were characterized by mass spectrometry and quantum chemical calculations. The experimental results demonstrated that the CoC anion can convert CO into CO.

Reactivity of Iron Hydride Anions FeH ( = 0-3) with Carbon Dioxide.

The hydrogenation of CO into value-added complexes is of great importance for both environmental and economic issues. Metal hydrides are good models for the active sites to explore the nature of CO hydrogenation; however, the fundamental insights into C-H bond formation are still far from clear because of the complexity of real-life catalysts. Herein, gas-phase reactions of the FeH ( = 0-3) anions with CO were investigated using mass spectrometry and quantum chemical calculations.

[Optimum selection of acupuncture treatment programs of cerebral infarction and its effects on insulin resistance].

Objective: To study the optimum acupuncture treatment program and the mechanism for treatment of cerebral infarction.

Methods: Sixty-three cases were randomly divided into 9 groups. The four factors, times of manipulation, the retaining time of the needle, acupuncture instrument and acupoints,and their corresponding three levels were adopted respectively in treatment of each group.