scholarly journals Photocatalytic Hydrogen Evolution Using Bi-Metallic (Ni/Pt) Na2Ti3O7 Whiskers: Effect of the Deposition Order

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 285 ◽  
Author(s):  
Luis F. Garay-Rodríguez ◽  
S. Murcia-López ◽  
T. Andreu ◽  
Edgar Moctezuma ◽  
Leticia M. Torres-Martínez ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Characterization ◽  
Sodium Titanate ◽  
H2 Production ◽  
Superior Performance ◽  
Hydrogen Yield ◽  
Wet Impregnation ◽  
X Ray ◽  
Co Catalysts ◽  
H2 Yield

Photocatalytic hydrogen production through ethanol photo-reforming using Na2Ti3O7 whiskers increases if the sodium titanate is decorated with well-known metallic catalysts such as Ni and Pt. Whereas wet impregnation with nickel gives only a slight increase in the activity, photo-deposition of Pt increased the H2 production by more than one order of magnitude. Through the combination of both co-catalysts (Ni and Pt) a superior performance in terms of H2 production is further observed. However, hydrogen yield is largely enhanced (almost three-fold), up to 778 μmol·g−1·h−1, if the Pt is photo-deposited on the surface of the catalyst before wet impregnation with Ni species (NTO/Pt/Ni) compared to H2 yield (283 μmol·g−1·h−1) achieved with the catalyst prepared in the reverse order (NTO/Ni/Pt). Structural, morphological, optical, and chemical characterization was carried out in order to correlate physicochemical properties with their photocatalytic activity. The X-ray photoelectron spectroscopy (XPS) results show a higher concentration of Pt2+ species if this metallic layer is under the nickel oxide layer. Moreover, X-ray diffraction patterns (XRD) show that Na2Ti3O7 surface is modified for both metal decoration processes.

scholarly journals Photocatalytic activity of graphene oxide–TiO 2 thin films sensitized by natural dyes extracted from Bactris guineensis

2019 ◽  
Vol 6 (3) ◽  
pp. 181824 ◽  
Author(s):  
William Vallejo ◽  
Angie Rueda ◽  
Carlos Díaz-Uribe ◽  
Carlos Grande ◽  
Patricia Quintana
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Graphene Oxide ◽  
Photocatalytic Degradation ◽  
Photoelectron Spectroscopy ◽  
Chemical Characterization ◽  
Sem Analysis ◽  
Visible Range ◽  
X Ray ◽  
Natural Sensitizer

This study synthesized and characterized composites of graphene oxide and TiO 2 (GO–TiO 2 ). GO–TiO 2 thin films were deposited using the doctor blade technique. Subsequently, the thin films were sensitized with a natural dye extracted from a Colombian source ( Bactris guineensis ). Thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements were used for physico-chemical characterization. All the samples were polycrystalline in nature, and the diffraction signals corresponded to the TiO 2 anatase crystalline phase. Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) verified the synthesis of composite thin films, and the SEM analysis confirmed the TiO 2 films morphological modification after the process of GO incorporation and sensitization. XPS results suggested a possibility of appearance of titanium (III) through the formation of oxygen vacancies (O v ). Furthermore, the optical results indicated that the presence of the natural sensitizer and GO improved the optical properties of TiO 2 in the visible range. Finally, the photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution, and pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. These results indicated that the presence of GO has an important synergistic effect in conjunction with the natural sensitizer, reaching a photocatalytic yield of 33%.

scholarly journals {CeO2/Bi2Mo1−xRuxO6} and {Au/Bi2Mo1−xRuxO6} Catalysts for Low-Temperature CO Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 947 ◽  
Author(s):  
Edson Edain González ◽  
Ricardo Rangel ◽  
Javier Lara ◽  
Pascual Bartolo-Pérez ◽  
Juan José Alvarado-Gil ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Photoelectron Spectroscopy ◽  
Supported Catalysts ◽  
Pollutant Emissions ◽  
Impregnation Method ◽  
Wet Impregnation ◽  
X Ray ◽  
Low Temperature Co Oxidation ◽  
Carbon Dioxide Co2 ◽  
Wet Impregnation Method

Nowadays, one of the most important challenges that humanity faces is to find alternative ways of reducing pollutant emissions. CeO2/Bi2Mo1−xRuxO6 and Au/Bi2Mo1−xRuxO6 catalysts were prepared to efficiently transform carbon monoxide (CO) to carbon dioxide (CO2) at low temperatures. The systems were prepared in a two-step process. First, Bi2Mo1−xRuxO6 supports were synthesized through the hydrothermal procedure under microwave heating. Then, CeO2 was deposited on Bi2Mo1−xRuxO6 using the wet impregnation method, while the incipient impregnation method was selected to deposit gold nanoparticles. The CeO2/Bi2Mo1−xRuxO6 and Au/Bi2Mo1−xRuxO6 catalysts were characterized using SEM microscopy and XRD. Furthermore, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used. Tests were carried out for the supported catalysts in CO oxidation, and high conversion values, nearing 100%, was observed in a temperature range of 100 to 250 °C. The results showed that the best system was the Au/Bi2Mo0.95Ru0.05O6 catalyst, with CO oxidation starting at 50 °C and reaching 100% conversion at 186 °C.

Anelastic Phenomena at the Fibre-Matrix Interface of the Ti6Al4V-SiCf Composite

2010 ◽  
Vol 425 ◽  
pp. 263-270 ◽  
Author(s):  
Paolo Deodati ◽  
Riccardo Donnini ◽  
Saulius Kaciulis ◽  
Alessio Mezzi ◽  
Roberto Montanari ◽  
...  
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Photoelectron Spectroscopy ◽  
Chemical Characterization ◽  
Matrix Interface ◽  
Ion Sputtering ◽  
Mechanical Spectroscopy ◽  
Monolithic Alloy ◽  
X Ray ◽  
Fibre Matrix

The composite, consisting of Ti6Al4V matrix reinforced by unidirectional SiC fibres (SCS-6), has been investigated by mechanical spectroscopy at temperatures up to 1,173 K. For comparison, the same experiments have been performed on the corresponding monolithic alloy. The internal friction (IF) spectrum of the composite exhibits a new relaxation peak superimposed to an exponentially increasing background. This peak, which is not present in the monolithic alloy, has an activation energy H = 186 kJ mol-1 and a relaxation time 0 = 2.3 x 10-15 s. The phenomenon has been attributed to a reorientation of interstitial-substitutional pairs in the  phase of Ti6Al4V matrix around the fibres. This explanation is supported by the results of micro-chemical characterization carried out by X-ray photoelectron spectroscopy (XPS) combined with Ar ion sputtering.

XPS Studies of the Interactions of Biocells with Various Silicon Based Surfaces

1995 ◽  
Vol 414 ◽  
Author(s):  
S. Seal ◽  
S. Krezoski ◽  
T. L. Barr ◽  
D. H. Petering
Keyword(s):  
Surface Chemistry ◽  
Tumor Cells ◽  
Photoelectron Spectroscopy ◽  
Freeze Drying ◽  
Chemical Characterization ◽  
Chrysotile Asbestos ◽  
X Ray ◽  
Silicon Based ◽  
Rat Tumor

AbstractSiliceous materials are the principal components of Earth's crust and also have become key ingredients of modem technology. Recently, we have expanded our chemical characterization of complex silicates (e.g., framework [1] and sheet types [2]) to include studies of their interaction with select biocells [3,4]. It is becoming apparent that the surface chemistry of these silicates, and perhaps that of silica itself, plays a key role in the oft resulting cell pathogenesis, thus enhancing the value of further investigations with X-ray photoelectron spectroscopy. The present research describes the unique growth of Ehrlich (murine or rat tumor) cells on Sio and SiO2 wafers, and also on select seaentine silicates (such as chrysotile asbestos). Tbese growth studies were followed by both cell/silicate separations and unique freeze drying [3,4]. XPS examination at select stages discovered cell induced alterations in the Si, O, Mg and particularly Fe chemistry of the silicon based systems as well as corresponding changes in the cell chemistry. Many of these features were confirmed by atomic absorption spectroscopy.

scholarly journals Metal and Precursor Effect during 1-Heptyne Selective Hydrogenation Using an Activated Carbon as Support

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Cecilia R. Lederhos ◽  
Juan M. Badano ◽  
Nicolas Carrara ◽  
Fernando Coloma-Pascual ◽  
M. Cristina Almansa ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Selective Hydrogenation ◽  
Photoelectron Spectroscopy ◽  
Palladium Catalysts ◽  
Active Sites ◽  
Ruthenium Catalysts ◽  
Superior Performance ◽  
Support Surface ◽  
Electronic Effects ◽  
X Ray

Palladium, platinum, and ruthenium supported on activated carbon were used as catalysts for the selective hydrogenation of 1-heptyne, a terminal alkyne. All catalysts were characterized by temperature programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. TPR and XPS suggest that the metal in all catalysts is reduced after the pretreatment with H2at 673 K. The TPR trace of the PdNRX catalyst shows that the support surface groups are greatly modified as a consequence of the use of HNO3during the catalyst preparation. During the hydrogenation of 1-heptyne, both palladium catalysts were more active and selective than the platinum and ruthenium catalysts. The activity order of the catalysts is as follows: PdClRX > PdNRX > PtClRX ≫ RuClRX. This superior performance of PdClRX was attributed in part to the total occupancy of the d electronic levels of the Pd metal that is supposed to promote the rupture of the H2bond during the hydrogenation reaction. The activity differences between PdClRX and PdNRX catalysts could be attributed to a better accessibility of the substrate to the active sites, as a consequence of steric and electronic effects of the superficial support groups. The order for the selectivity to 1-heptene is as follows: PdClRX = PdNRX > RuClRX > PtClRX, and it can be mainly attributed to thermodynamic effects.

scholarly journals Pt Deposites on TiO2 for Photocatalytic H2 Evolution: Pt Is Not Only the Cocatalyst, but Also the Defect Repair Agent

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1047 ◽  
Author(s):  
Zhan Shu ◽  
Yandi Cai ◽  
Jiawei Ji ◽  
Changjin Tang ◽  
Shuohan Yu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Charge Separation ◽  
H2 Production ◽  
H2 Evolution ◽  
X Ray ◽  
Production Activity ◽  
Defect Repair ◽  
New Perspective ◽  
Photocatalytic H2 Evolution

Pt, as a common cocatalyst, has been widely used in photocatalytic H2 evolution. However, the specific role of Pt in photocatalytic H2 evolution has not been thoroughly studied. In this paper, by employing three Pt sources with different charges (positive, negative and neutral), we systematically studied the charge effect of Pt sources on photocatalytic H2 evolution via TiO2 catalyst. According to the results of Raman, X-ray photoelectron spectroscopy (XPS), recycle experiments and photocurrent characterizations, it was found that TiO2 would produce electropositive defects during photocatalytic H2 evolution, inevitably leading to the decline of H2 production activity. Thanks to the electrostatic interaction, the electronegative Pt source not only promoted charge separation, but preferential deposited on electropositive defects, which acted as the defect repair agent, and thus resulted in the increased photocatalytic stability. This work may provide a new perspective for enhancing photocatalytic stability of hydrogen production.

Preparation and Properties of Eu3+-Doped TiO2 Nanowires

2012 ◽  
Vol 624 ◽  
pp. 67-71
Author(s):  
Si Qin Zhao ◽  
Hong Liang Wan ◽  
S. Asuha
Keyword(s):  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Sodium Titanate ◽  
X Ray ◽  
Valence States ◽  
Photocatalytic Activities ◽  
Crystallite Sizes ◽  
Degradation Of Methyl Orange

Nanowires of sodium titanate, TiO2 and Eu3+/TiO2 were synthesized by hydrothermal method, and their microstructure, optical properties and valence states of exterior elements were characterized by X-ray powder diffraction (XRD), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy techniques. At the same time, the photocatalytic activities of the materials for degradation of methyl orange under visible-light irradiation were also investigated. The results showed the formation of nanowires of sodium titanate with average crystallite sizes of 50-200 nm and in lengths from several microns to several dozens microns, and its chemical formula was determined to be Na2Ti3O7. TiO2 and Eu3+ /TiO2nanowires were prepared from the Na2Ti3O7 nanowires via ion exchange (i.e., with H+ and Eu3+ ions) and high temperature sintering processes. These three kinds of nanowires showed different photocatalytic activities for degradation of methyl orange. Na2Ti3O7 nanowire did not show any photocatalytic activity for methyl orange degradation, while TiO2 nanowire was superior to Na2Ti3O7 nanowire; and, Eu3+/ TiO2 nanowire possessed the highest photocatalytic activity.

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