First-principles kinetics study of carbon monoxide promoted Ostwald ripening of Au particles on FeO/Pt(111)

The dynamic and kinetic evolution of supported metal particles in the presence of reactants is decisive in shaping the nature of the catalytic active sites and the deactivation process. Ostwald ripening of FeO/Pt(111) supported Au particles in the presence of carbon monoxide is addressed here by firstprinciples kinetics. It is found that CO stabilizes the ripening monomer(Au atom) by forming favorable Au carbonyls with lower total activation energy, and corresponding phase diagram at wide range of temperature and CO pressures is constructed. Evolution of particle number, dispersion and particle size distribution of supported Au particles are explored. Great influence of CO promotion on ripening kinetics is revealed and explored in details, and mbar range of CO can lower the onset temperature of ripening by a few hundred kelvins. The present work reveals the crucial role of the metal-reactant complexes formed under reaction conditions on ripening of metal catalysts.

Creatine kinase in the diagnosis and prognostic prediction of amyotrophic lateral sclerosis:a retrospective case-control study

Creatine kinase is a muscle enzyme that has been reported at various levels in different studies involving patients with amyotrophic lateral sclerosis.In the present retrospective case-control study,we included 582 patients with amyotrophic lateral sclerosis and 582 age-and sexmatched healthy controls.All amyotrophic lateral sclerosis participants received treatment in the Department of Neurology,West China Hospital,China,between May 2008 and December 2018.Serum creatine kinase levels in patients with amyotrophic lateral sclerosis were significantly higher than those in healthy controls.Subgroup analysis revealed that serum creatine kinase levels in men were higher than those in women in both amyotrophic lateral sclerosis patients and healthy controls.Compared with patients with bulbar-onset amyotrophic lateral sclerosis,patients with limb-onset amyotrophic lateral sclerosis had higher creatine kinase levels.Spearman's correlation analysis revealed that serum creatine kinase levels were not correlated with body mass index,Amyotrophic lateral Sclerosis Functional Rating ScaleRevised score,or progression rate.After adjusting for prognostic covariates,higher log creatine kinase values were correlated with higher overall survival in the amyotrophic lateral sclerosis patients.We also investigated the longitudinal changes in serum creatine kinase levels in 81 amyotrophic lateral sclerosis patients;serum creatine kinase levels were decreased at the second blood test,which was sampled at least 6 months after the first blood test.Together,our results suggest that serum creatine kinase levels can be used as an independent factor for predicting the prognosis of amyotrophic lateral sclerosis patients.This study received ethical approval from the Ethics Committee of West China Hospital,China(approval No.2015(236))on December 23,2015.

First-Principles Microkinetic Study of Methanol Synthesis on Cu(221)and ZnCu(221)Surfaces

First-principle based microkinetic simulations are performed to investigate methanol synthesis from CO and CO2 on Cu(221)and CuZn(221)surfaces.It is found that regardless of surface structure,the carbon consumption rate follows the order:CO hydrogenation>CO/CO2 hydrogenation>CO2 hydrogenation.The superior CO hydrogenation activity mainly arises from the lower barriers of elementary reactions than CO2 hydrogenation.Compared to Cu(221),the introduction of Zn greatly lowers the activity of methanol synthesis,in particularly for CO hydrogenation.For a mixed CO/CO2 hydrogenation,CO acts as the carbon source on Cu(221)while both CO and CO2 contribute to carbon conversion on CuZn(221).The degree of rate control studies show that the key steps that determine the reaction activity of CO/CO2 hydrogenation are HCO and HCOO hydrogenation on Cu(221),instead of HCOOH hydrogenation on CuZn(221).The present work highlights the effect of the Zn doping and feed gas composition on methanol synthesis.

Dynamic chemical processes on ZnO surfaces tuned by physisorption under ambient conditions

The catalytic properties of non-reducible metal oxides have intrigued continuous interest in the past decades.Often time,catalytic studies of bulk non-reducible oxides focused on their high-temperature applications owing to their weak interaction with small molecules.Hereby,combining ambient-pressure scanning tunneling microscopy(AP-STM),AP X-ray photoelectron spectroscopy(AP-XPS)and density functional theory(DFT)calculations,we studied the activation of CO and CO_(2)on ZnO,a typical nonreducible oxide and major catalytic material in the conversion of C1 molecules.By visualizing the chemical processes on ZnO surfaces at the atomic scale under AP conditions,we showed that new adsorbate structures induced by the enhanced physisorption and the concerted interaction of physisorbed molecules could facilitate the activation of CO and CO_(2)on ZnO.The reactivity of ZnO towards CO could be observed under AP conditions,where an ordered(2×1)–CO structure was observed on ZnO(1010).Meanwhile,chemisorption of CO_(2)on ZnO(1010)under AP conditions was also enhanced by physisorbed CO_(2),which minimizes the repulsion between surface dipoles and causes a(3×1)–CO_(2)structure.Our study has brought molecular insight into the fundamental chemistry and catalytic properties of ZnO surfaces under realistic reaction conditions.

Synthesis of Iron-Carbide Nanoparticles:Identification of the Active Phase and Mechanism of Fe-Based Fischer-Tropsch Synthesis

Despite the extensive study of the Fe-based Fischer-Tropsch synthesis(FTS)over the past 90 years,its active phases and reaction mechanisms are still unclear due to the coexistence of metals,oxides,and carbide phases presented under realistic FTS reaction conditions and the complex reaction network involving CO activation,C-C coupling,and methane formation.To address these issues,we successfully synthesized a range of pure-phase iron and iron-carbide nanoparticles(Fe,Fe_(5)C_(2),Fe_(3)C,and Fe_(7)C_(3))for the first time.By using them as the ideal model catalysts on high-pressure transient experiments,we identified unambiguously that all the iron carbides are catalytically active in the FTS reaction while Fe_(5)C_(2) is the most active yet stable carbide phase,consistent with density functional theory(DFT)calculation results.The reaction mechanism and kinetics of Fe-based FTS were further explored on the basis of those model catalysts by means of transient high-pressure stepwise temperature-programmed surface reaction(STPSR)experiments and DFT calculations.Our work provides new insights into the active phase of iron carbides and corresponding FTS reaction mechanism,which is essential for better iron-based catalyst design for FTS reactions.

Incorporating Sulfur Atoms into Palladium Catalysts by Reactive Metal–Support Interaction for Selective Hydrogenation

Developing highly active and selective catalysts for the hydrogenation of nitroarenes,an environmentally benign process to produce industrially important aniline intermediates,is highly desirable but very challenging.Pd catalysts are generally recognized as active but nonselective catalysts for this important reaction.Here,we report an effective strategy to greatly improve the selectivity of Pd catalysts based on the reactive metal–support interaction.

An Integrated Carbon Dioxide Capture and Methanation Process

Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.