Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Review of Scientific Instruments and may be found at https://aip.scitation.org/doi/10.1063/1.4946877.Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily

Design of a new reactor-like high temperature near ambient pressure scanning tunneling microscope for catalysis studies

This is the published version. ©Copyright 2013 American Institute of PhysicsHere, we present the design of a new reactor-like high-temperature near ambient pressure scanning tunneling microscope (HT-NAP-STM) for catalysis studies. This HT-NAP-STM was designed for exploration of structures of catalyst surfaces at atomic scale during catalysis or under reaction conditions. In this HT-NAP-STM, the minimized reactor with a volume of reactant gases of ∼10 ml is thermally isolated from the STM room through a shielding dome installed between the reactor and STM room. An aperture on the dome was made to allow tip to approach to or retract from a catalyst surface in the reactor. This dome minimizes thermal diffusion from hot gas of the reactor to the STM room and thus remains STM head at a constant temperature near to room temperature, allowing observation of surface structures at atomic scale under reaction conditions or during catalysis with minimized thermal drift. The integrated quadrupole mass spectrometer can simultaneously measure products during visualization of surface structure of a catalyst. This synergy allows building an intrinsic correlation between surface structure and its catalytic performance. This correlation offers important insights for understanding of catalysis. Tests were done on graphite in ambient environment, Pt(111) in CO, graphene on Ru(0001) in UHV at high temperature and gaseous environment at high temperature. Atom-resolved surface structure of graphene on Ru(0001) at 500 K in a gaseous environment of 25 Torr was identified

Action of bimetallic nanocatalysts under reaction conditions and during catalysis: evolution of chemistry from high vacuum conditions to reaction conditions

This is the published version. Copyright 2012 Royal Society of ChemistryBimetallic catalysts are one of the main categories of metal catalysts due to the tunability of electronic and geometric structures through alloying a second metal. The integration of a second metal creates a vast number of possibilities for varying the surface structure and composition of metal catalysts toward designing new catalysts. It is well acknowledged that the surface composition, atomic arrangement, and electronic state of bimetallic catalysts could be different from those before a chemical reaction or catalysis based on ex situ studies. Thanks to advances in electron-based surface analytical techniques, the surface chemistry and structure of bimetallic nanoparticles can be characterized under reaction conditions and during catalysis using ambient pressure analytical techniques including ambient pressure XPS, ambient pressure STM, X-ray absorption spectroscopy and others. These ambient pressure studies revealed various restructurings in the composition and arrangement of atoms in the surface region of catalysts under reaction conditions or during catalysis compared to that before reaction. These restructurings are driven by thermodynamic and kinetic factors. The surface energy of the constituent metals and adsorption energy of reactant molecules or dissociated species on a metal component are two main factors from the point of view of thermodynamics. Correlations between the authentic surface structure and chemistry of catalysts during catalysis and simultaneous catalytic performance were built for understanding catalytic mechanisms of bimetallic catalysts toward designing new catalysts with high activity, selectivity, and durability

Generative Adversarial Mapping Networks

Generative Adversarial Networks (GANs) have shown impressive performance in generating photo-realistic images. They fit generative models by minimizing certain distance measure between the real image distribution and the generated data distribution. Several distance measures have been used, such as Jensen-Shannon divergence, $f$-divergence, and Wasserstein distance, and choosing an appropriate distance measure is very important for training the generative network. In this paper, we choose to use the maximum mean discrepancy (MMD) as the distance metric, which has several nice theoretical guarantees. In fact, generative moment matching network (GMMN) (Li, Swersky, and Zemel 2015) is such a generative model which contains only one generator network $G$ trained by directly minimizing MMD between the real and generated distributions. However, it fails to generate meaningful samples on challenging benchmark datasets, such as CIFAR-10 and LSUN. To improve on GMMN, we propose to add an extra network $F$, called mapper. $F$ maps both real data distribution and generated data distribution from the original data space to a feature representation space $\mathcal{R}$, and it is trained to maximize MMD between the two mapped distributions in $\mathcal{R}$, while the generator $G$ tries to minimize the MMD. We call the new model generative adversarial mapping networks (GAMNs). We demonstrate that the adversarial mapper $F$ can help $G$ to better capture the underlying data distribution. We also show that GAMN significantly outperforms GMMN, and is also superior to or comparable with other state-of-the-art GAN based methods on MNIST, CIFAR-10 and LSUN-Bedrooms datasets.Comment: 9 pages, 7 figure

A Lifting Relation from Macroscopic Variables to Mesoscopic Variables in Lattice Boltzmann Method: Derivation, Numerical Assessments and Coupling Computations Validation

In this paper, analytic relations between the macroscopic variables and the mesoscopic variables are derived for lattice Boltzmann methods (LBM). The analytic relations are achieved by two different methods for the exchange from velocity fields of finite-type methods to the single particle distribution functions of LBM. The numerical errors of reconstructing the single particle distribution functions and the non-equilibrium distribution function by macroscopic fields are investigated. Results show that their accuracy is better than the existing ones. The proposed reconstruction operator has been used to implement the coupling computations of LBM and macro-numerical methods of FVM. The lid-driven cavity flow is chosen to carry out the coupling computations based on the numerical strategies of domain decomposition methods (DDM). The numerical results show that the proposed lifting relations are accurate and robust

The relationship between job performance and perceived organizational support in faculty members at Chinese universities: a questionnaire survey

BACKGROUND: Although several studies have been conducted to investigate the relationship between perceived organizational support (POS) and job performance (JP), it remains unclear whether this relationship is appropriate for faculty members at Chinese universities. The objectives of this study were to (a) examine the correlation between POS andJP; (b) identify the predictors of POS, including demographic and organizational characteristics among faculty members at a Chinese university; (c) investigate the influence of mediating factors between POS and JP; and (d) compare the findings of this study with related studies. METHODS: A cross-sectional questionnaire survey was used in this study. The questionnaire was administered to 700 faculty members who were randomly selected from all faculty members at six universities. A total of 581 questionnaires were obtained. A statistical model for JP was developed based on the literature review. RESULTS: The analysis results indicated that the relationship between POS and JP was mediated by job satisfaction (JS), positive affectivity (PA), and affective commitment (AC). In addition, procedural and distributive justice contribute to POS. CONCLUSIONS: The study concludes that the relationship between POS and JP is mediated by JS, PA, and AC and is influenced by POS. These results can provide evidence for university administrators to improve POS and increase the JP of faculty members at universities

catena-Poly[[[bis­(4-methyl­benzoato-κ2 O,O′)zinc(II)]-μ-4,4′-bipyridine-κ2 N:N′] tetra­hydrate]

The asymmetric unit of the title compound, {[Zn(C7H7O2)2(C10H8N2)]·4H2O}n, contains a highly distorted octa­hedral ZnII metal center strongly coordinated by two N atoms of two 4,4′-bipyridine (4,4′-bipy) ligands and chelated by two 4-methyl­benzoate anions. The crystallographic inversion center and glide plane present at the center of the C—C single bond of 4,4′-bipy, along with the cis coordination motif of the 4,4′-bipy, lead to one-dimensional zigzag chains. There are a large number of water mol­ecules in the crystal structure, which also form one-dimensional chains through O—H⋯O hydrogen bonds

Effect of congenital ptosis on astigmatism and axis length

AIM: To investigate the effects of congenital ptosis degree on total astigmatism, corneal astigmatism, intraocular astigmatism and axis length, and to discuss the relation with amblyopia. <p>METHODS: Fifty patients(100 eyes)with congenital ptosis were selected and divided into four groups: 33 eyes in group Ⅰ(normal); 20 eyes in group Ⅱ(mild); 17 eyes in group Ⅲ(moderate); 30 eyes in group Ⅳ(severity). Firstly, they received standardized medical optometry. Absolute value of astigmatism was recorded as total astigmatism. Then, corneal topography was used to measure double eyes for at least 3 times, and the best results were used to record the SimK. Define absolute value of △SimK as corneal astigmatism. Finally, axial length was measured for 5 times by A super-measurement, and take the mean value. Formula: intraocular astigmatism=total astigmatism-corneal astigmatism.<p>RESULTS: There was a significance difference between total astigmatism and cornea astigmatism(<i>P</i>=0.000, 0.002<0.05). Also they were positive correlation with severity of ptosis(Spearman <i>r</i>_s=0.514, 0.721,<i>P</i><0.05), but there was not significance difference in axial orientation, intraocular astigmatism and axial length(all <i>P</i>>0.05). The axial orientation, intraocular astigmatism had no correlation with severity of ptosis.<p>CONCLUSION: The congenital ptosis affects on eye astigmatism through the change of cornea astigmatism, which is related to severity of ptosis, but has no effect on axial length. The rate of amblyopia is higher than normal on congenital ptosisespecially severity. Amblyopia is related to high astigmatism which is moderate astigmatism with rule