Surface of a catalyst in a gas phase

Tang, Yu; Nguyen, Luan; Li, Yuting; Wang, Nan; Tao, Franklin Feng

doi:10.1016/j.coche.2016.02.007

Cited by 10 publications

(9 citation statements)

References 33 publications

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“…This AP-XPS uses a monochromated Al Kα X-ray source to generate photoelectrons. A new high-temperature reaction cell was designed and built by the Tao group . This home-built AP-XPS system equipped with a new reaction cell has been previously used in tracking the surface chemistry of catalysts under reaction conditions and during catalysis. ,− The catalyst particles were loaded on a roughened silver foil affixed onto a sample holder.…”

Section: Methodsmentioning

confidence: 99%

“…In situ/operando characterization of the surface of the 15.0 wt % NiO/CeO 2 catalyst during catalysis was carried out using the lab-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS) system built by the Tao group. 31 This AP-XPS uses a monochromated Al Kα X-ray source to generate photoelectrons. A new high-temperature reaction cell was designed and built by the Tao group.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

See 1 more Smart Citation

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO₂ Nanorods through Synergistic Effect

Zhang

House

Tang

et al. 2018

ACS Sustainable Chem. Eng.

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Catalytic complete oxidation of CH4 at relatively low temperatures is significant for removing unburned CH4 from the exhaust of combustion engines fueled with natural gas or liquefied petroleum gas. Here a nanocomposite catalyst (NiO/CeO2) consisting of CeO2 nanorods and supported NiO nanoclusters was prepared by a two-step wet-chemistry method. This nanocomposite catalyst exhibits high catalytic activity for the complete oxidation of CH4 in the temperature range of 350–600 °C. A CH3-like intermediate bound to Ni cations was observed at a relatively low temperature by ambient pressure X-ray photoelectron spectroscopy under catalytic conditions. Parallel kinetic studies of NiO/SiO2, CeO2 and NiO/CeO2 catalysts show that the apparent barrier for complete oxidation of CH4 on NiO/CeO2 (69.4 ± 4 kJ/mol) is much lower than the 95.1 ± 5 kJ/mol of pure CeO2 and 98.4 ± 5 kJ/mol of NiO/SiO2, supported by the turnover frequency of NiO/CeO2 being significantly higher than NiO/SiO2 and CeO2. These differences indicate a synergistic effect between the CeO2 nanorods and the supported NiO nanoclusters. This synergistic effect occurs at the interface of NiO and CeO2, observed in TEM. The lattice oxygen atoms at the interface exhibit high activity based on the lower reduction temperature uncovered in studies of the temperature-programmed reduction of H2.

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Section: Methodsmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO₂ Nanorods through Synergistic Effect

Zhang

House

Tang

et al. 2018

ACS Sustainable Chem. Eng.

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“…franklin.tao.2011@gmail.com of temperature or/and pressure-dependent entropy could restructure the catalyst surface, the chemistry and structure of an active catalyst surface in a reactant gas cannot be simply extrapolated from the surface chemistry and structure identified in ultrahigh vacuum (UHV) condition. [7][8][9][10][11][12] From this point of view, tracking surface chemistry and structure of the catalyst in a gas environment of one or more reactants at a specific pressure or/and temperature is necessary. Unfortunately, in most cases, an electron gun of X-ray source and an electrostatic lens of energy analyzer must be performed in a high vacuum condition.…”

Section: Introductionmentioning

confidence: 99%

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

Nguyen

Tao

2016

Review of Scientific Instruments

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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.

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“…The need to clarify these structure-property relationships in catalyst materials has spurred the adaption of several surface characterization techniques [4][5][6][7] , including infrared (IR) absorption spectroscopy 8 , synchrotron X-ray-based methods 9 , and X-ray photoelectron spectroscopy 10,11 , to enable measurements during reactions and at realistic gas pressures. However, these approaches typically look at bulk single-crystal surfaces, and so, it is not straightforward to extrapolate their results towards the actual behavior of NP catalysts.…”

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confidence: 99%

Structural changes in noble metal nanoparticles during CO oxidation and their impact on catalyst activity

Chee

Arce‐Ramos

et al. 2020

Nat Commun

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The dynamical structure of a catalyst determines the availability of active sites on its surface. However, how nanoparticle (NP) catalysts restructure under reaction conditions and how these changes associate with catalytic activity remains poorly understood. Using operando transmission electron microscopy, we show that Pd NPs exhibit reversible structural and activity changes during heating and cooling in mixed gas environments containing O 2 and CO. Below 400°C, the NPs form flat low index facets and are inactive towards CO oxidation. Above 400°C, the NPs become rounder, and conversion of CO to CO 2 increases significantly. This behavior reverses when the temperature is later reduced. Pt and Rh NPs under similar conditions do not exhibit such reversible transformations. We propose that adsorbed CO molecules suppress the activity of Pd NPs at lower temperatures by stabilizing low index facets and reducing the number of active sites. This hypothesis is supported by thermodynamic calculations.

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Surface of a catalyst in a gas phase

Cited by 10 publications

References 33 publications

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO₂ Nanorods through Synergistic Effect

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO₂ Nanorods through Synergistic Effect

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

Structural changes in noble metal nanoparticles during CO oxidation and their impact on catalyst activity

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Surface of a catalyst in a gas phase

Cited by 10 publications

References 33 publications

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO2 Nanorods through Synergistic Effect

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO2 Nanorods through Synergistic Effect

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

Structural changes in noble metal nanoparticles during CO oxidation and their impact on catalyst activity

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Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO₂ Nanorods through Synergistic Effect

Complete Oxidation of Methane on NiO Nanoclusters Supported on CeO₂ Nanorods through Synergistic Effect