Surface and bulk properties, catalytic activities and selectivities in methane oxidation on near-stoichiometric calcium hydroxyapatites

1996 ◽  
Vol 6 (3) ◽  
pp. 459 ◽  
Author(s):  
Shigeru Sugiyama ◽  
Toshimitsu Minami ◽  
Toshihiro Moriga ◽  
Hiromu Hayashi ◽  
Kichiro Koto ◽  
...  
Keyword(s):  
Methane Oxidation ◽  
Bulk Properties ◽  
Catalytic Activities

CATALYTIC ACTIVITY FOR METHANE OXIDATION OF GOETHITE SUPPORTED ON ALUMINA

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4249-4254 ◽  
Author(s):  
KEI-ICHIRO MURAI ◽  
KOHEI TOMITA ◽  
SUGURU TOJO ◽  
TOSHIHIRO MORIGA ◽  
ICHIRO NAKABAYASHI
Keyword(s):  
Catalytic Activity ◽  
Specific Surface ◽  
Methane Oxidation ◽  
Model Experiment ◽  
The Other ◽  
Catalytic Activities ◽  
Surface Areas ◽  
Oxidation Of Methane ◽  
Other Hand ◽  
Specific Surface Areas

Two kinds of α- Fe 2 O 3 catalysts supported on χ- Al 2 O 3 and γ- Al 2 O 3 were synthesized. α- Fe 2 O 3 was prepared from α- FeOOH . As a model experiment, an investigation was made with the oxidation of methane. As all catalysts with various Fe contents supported on χ- Al 2 O 3 with various Fe contents had higher specific surface areas than those supported on γ- Al 2 O 3, α- Fe 2 O 3/χ- Al 2 O 3 catalyst has higher catalytic activities than α- Fe 2 O 3/γ- Al 2 O 3 catalyst. From SEM-EDS analyses, it is concluded that in α- Fe 2 O 3/χ- Al 2 O 3 catalyst, α- Fe 2 O 3 exists mainly on the surface of the support, because of flatness of the surface of χ- Al 2 O 3. On the other hand, in the case of α- Fe 2 O 3/γ- Al 2 O 3 catalyst, as the surface of support, γ- Al 2 O 3, is uneven, α- Fe 2 O 3 do not partially exist on the surface but in the pores.

Methane Oxidation on a Coverage Layer Study

2008 ◽  
Author(s):  
Juliana L. Rose ◽  
Pedro Paulo F. Gouvêa ◽  
Cláudio F. Mahler
Keyword(s):  
Methane Oxidation

Photocatalytic activity of TiO2 synthesized by anodization and anodic spark deposition

MRS Advances ◽  
2020 ◽  
Vol 5 (61) ◽  
pp. 3141-3152
Author(s):  
Alma C. Chávez-Mejía ◽  
Génesis Villegas-Suárez ◽  
Paloma I. Zaragoza-Sánchez ◽  
Rafael Magaña-López ◽  
Julio C. Morales-Mejía ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Activity ◽  
Surface Characteristics ◽  
Amorphous Solids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalytic Activities ◽  
Anodic Spark Oxidation ◽  
Porous Surfaces ◽  
Scanning Electron

AbstractSeveral photocatalysts, based on titanium dioxide, were synthesized by spark anodization techniques and anodic spark oxidation. Photocatalytic activity was determined by methylene blue oxidation and the catalytic activities of the catalysts were evaluated after 70 hours of reaction. Scanning Electron Microscopy and X Ray Diffraction analysis were used to characterize the catalysts. The photocatalyst prepared with a solution of sulfuric acid and 100 V presented the best performance in terms of oxidation of the dye (62%). The electric potential during the synthesis (10 V, low potential; 100 V, high potential) affected the surface characteristics: under low potential, catalyst presented smooth and homogeneous surfaces with spots (high TiO2 concentration) of amorphous solids; under low potential, catalyst presented porous surfaces with crystalline solids homogeneously distributed.

Atomistic Simulation Study of Controlled Nanostructure Patterning

2003 ◽  
Vol 775 ◽  
Author(s):  
Byeongchan Lee ◽  
Kyeongjae Cho
Keyword(s):  
Diffusion Barrier ◽  
Atomistic Simulation ◽  
Degrees Of Freedom ◽  
Embedded Atom Method ◽  
Surface Kinetics ◽  
Bulk Properties ◽  
Embedded Atom ◽  
Kinetics Of ◽  
Dissociation Barrier ◽  
Strain Dependent

AbstractWe investigate the surface kinetics of Pt using the extended embedded-atom method, an extension of the embedded-atom method with additional degrees of freedom to include the nonbulk data from lower-coordinated systems as well as the bulk properties. The surface energies of the clean Pt (111) and Pt (100) surfaces are found to be 0.13 eV and 0.147 eV respectively, in excellent agreement with experiment. The Pt on Pt (111) adatom diffusion barrier is found to be 0.38 eV and predicted to be strongly strain-dependent, indicating that, in the compressive domain, adatoms are unstable and the diffusion barrier is lower; the nucleation occurs in the tensile domain. In addition, the dissociation barrier from the dimer configuration is found to be 0.82 eV. Therefore, we expect that atoms, once coalesced, are unlikely to dissociate into single adatoms. This essentially tells that by changing the applied strain, we can control the patterning of nanostructures on the metal surface.

Metal-Assisted Plasma Etching of Silicon: A Liquid-Free Alternative to MACE

2018 ◽  
Author(s):  
Julia Sun ◽  
Benjamin Almquist
Keyword(s):  
Liquid Phase ◽  
Plasma Etching ◽  
Chemical Etching ◽  
Gold Films ◽  
Metallic Films ◽  
Au Catalyst ◽  
Feed Concentration ◽  
Catalytic Activities ◽  
Metal Assisted Chemical Etching ◽  
Complex Nanostructures

For decades, fabrication of semiconductor devices has utilized well-established etching techniques to create complex nanostructures in silicon. Of these, two of the most common are reactive ion etching in the gaseous phase and metal-assisted chemical etching (MACE) in the liquid phase. Though these two methods are highly established and characterized, there is a surprising scarcity of reports exploring the ability of metallic films to catalytically enhance the etching of silicon in dry plasmas via a MACE-like mechanism. Here, we discuss a <u>m</u>etal-<u>a</u>ssisted <u>p</u>lasma <u>e</u>tch (MAPE) performed using patterned gold films to catalyze the etching of silicon in an SF<sub>6</sub>/O<sub>2</sub> mixed plasma, selectively increasing the rate of etching by over 1000%. The degree of enhancement as a function of Au catalyst configuration and relative oxygen feed concentration is characterized, along with the catalytic activities of other common MACE metals including Ag, Pt, and Cu. Finally, methods of controlling the etch process are briefly explored to demonstrate the potential for use as a liquid-free fabrication strategy.

Ultra-Low Amounts of Palladium (0.005-0.05 Wt% Pd) Supported on Titania: Remarkable Low-Temperature Activity for NO Reduction with CO and Structure-Function Property Relationships in Methane Oxidation

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Libor Kovarik ◽  
Nicholas R. Jaegers ◽  
János Szanyi ◽  
Yong Wang
Keyword(s):  
Nitric Oxide ◽  
Carbon Monoxide ◽  
Methane Oxidation ◽  
Steam Reforming ◽  
Methane Steam Reforming ◽  
Oxide Reduction ◽  
Water Steam ◽  
Methane Steam ◽  
Anatase Titania ◽  
Nitric Oxide Reduction

<p>Atomically dispersed Pd +2 cations with ultra-dilute loading of palladium (0.005-0.05 wt%) were anchored on anatase titania and characterized with FTIR, microscopy and catalytic tests. CO infrared adsorption produces a sharp, narrow mono-carbonyl Pd(II)-CO band at ~2,130 cm<sup>-1</sup> indicating formation of highly uniform and stable Pd+2 ions on anatase titania. The 0.05 wt% Pd/TiO<sub>2</sub> sample was evaluated for methane combustion under dry and wet (industrially relevant) conditions in the presence and absence of carbon monoxide. Notably, we find the isolated palladium atoms respond dynamically upon oxygen concentration modulation (switching-on and switching off). When oxygen is removed from the wet methane stream, palladium ions are reduced to metallic state by methane and catalyze methane steam reforming instead of complete methane oxidation. Re-admission of oxygen restores Pd<sup>+2</sup> cations and switches off methane steam reforming activity. Moreover, 0.05 wt% Pd/TiO<sub>2</sub> is a competent CO oxidation catalyst in the presence of water steam with 90% CO conversion and TOF ~ 4,000 hr<sup>-1</sup> at 260 ⁰C. </p><p>More importantly, we find that diluting 0.05 wt% Pd/titania sample with titania to ultra-low 0.005 wt% palladium loading produces a remarkably active material for nitric oxide reduction with carbon monoxide under industrially relevant conditions with >90% conversion of nitric oxide at 180 ⁰C (~460 ppm NO and 150 L/g*hr flow rate in the presence of >2% water steam) and TOF ~6,000 hr<sup>-1</sup>. Pd thus outperforms state-of-the-art rhodium containing catalysts with (15-20 times higher rhodium loading; rhodium is ~ 3 times more expensive than palladium). Furthermore, palladium catalysts are more selective towards nitrogen and produce significantly less ammonia relative to the more traditional rhodium catalysts due to lower Pd amount nd lower water-gas-shift activity. Our study is the first example of utilizing ultra-low (0.05 wt% and less) noble metal (Pd) amounts to produce heterogeneous catalysts with extraordinary activity for nitric oxide reduction. This opens up a pathway to study other Pd, Pt and Rh containing materials with ultra-low loadings of expensive noble metals dispersed on titania or titania-coated oxides for industrially relevant nitric oxide abatement.</p>

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