scholarly journals Evolution of anatase surface active sites probed by in situ sum-frequency phonon spectroscopy

2016 ◽  
Vol 2 (9) ◽  
pp. e1601162 ◽  
Author(s):  
Yue Cao ◽  
Shiyou Chen ◽  
Yadong Li ◽  
Yi Gao ◽  
Deheng Yang ◽  
...  
Keyword(s):  
Active Sites ◽  
Oxygen Vacancies ◽  
Surface Reactivity ◽  
Ambient Conditions ◽  
Sum Frequency ◽  
Surface Active ◽  
Surface Phonon Mode ◽  
Titanium Dioxides ◽  
Associated Species

Surface active sites of crystals often govern their relevant surface chemistry, yet to monitor them in situ in real atmosphere remains a challenge. Using surface-specific sum-frequency spectroscopy, we identified the surface phonon mode associated with the active sites of undercoordinated titanium ions and conjoint oxygen vacancies, and used it to monitor them on anatase (TiO2) (101) under ambient conditions. In conjunction with theory, we determined related surface structure around the active sites and tracked the evolution of oxygen vacancies under ultraviolet irradiation. We further found that unlike in vacuum, the surface oxygen vacancies, which dominate the surface reactivity, are strongly regulated by ambient gas molecules, including methanol and water, as well as weakly associated species, such as nitrogen and hydrogen. The result revealed a rich interplay between prevailing ambient species and surface reactivity, which can be omnipresent in environmental and catalytic applications of titanium dioxides.

Directly monitoring the active sites of charge transfer in heterocycles in situ and in real time

2019 ◽  
Vol 55 (4) ◽  
pp. 541-544 ◽  
Author(s):  
Shuji Ye ◽  
Junjun Tan ◽  
Kangzhen Tian ◽  
Chuanzhao Li ◽  
Jiahui Zhang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Real Time ◽  
Vibrational Spectroscopy ◽  
Active Sites ◽  
Electronic States ◽  
Sum Frequency Generation ◽  
Vibrational Modes ◽  
Label Free ◽  
Sum Frequency

Coherent degenerate infrared-infrared-visible sum frequency generation vibrational spectroscopy provides a powerful label-free probe for identifying the vibrational modes that are coupled through the electronic states in situ and in real time.

Metalloporphyrin immobilized CeO2: in situ generation of active sites and synergistic promotion of photocatalytic water oxidation

2021 ◽  
Author(s):  
Jiao Meng ◽  
Yue Zhao ◽  
Haining Li ◽  
Ruiping Chen ◽  
Xun Sun ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Electron Coupling ◽  
Catalytically Active ◽  
In Situ Generation ◽  
The Creation

CoTCPP transfer photoexcited electrons to CeO2 by d–f electron coupling. The in situ generation of catalytically active sites: reduction on CeO2 accompanied with the creation of oxygen vacancies and oxidation on CoTCPP that transforms into CoOOH.

scholarly journals The effect of precursors salts on surface state of Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts

2004 ◽  
Vol 76 (4) ◽  
pp. 825-832 ◽  
Author(s):  
André L. Guimarães ◽  
Lídia C. Dieguez ◽  
Martin Schmal
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Oxygen Storage ◽  
Promoting Effect ◽  
X Ray ◽  
Surface Active ◽  
Al2o3 Catalyst

The influence of the precursors on the promoting effect of ceria on Pd/Al2O3 catalyst, when ceria is coated over alumina was studied. The reaction of propane oxidation proceeded under different feed conditions and the surface active sites were characterized by X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance spectroscopy (DRS). XPS and DRS results show that PdO/Pd0 interface are the active sites independent of the precursor, while the catalysts containing CeO2 showed formation of palladium species in the highest oxidation state, probably PdO2 (338 eV) after the oxidation of propane. Besides, the O/Al and O/Ce ratios evidenced the increase of oxygen storage in the presence of CeO2. In addition, the precursor acetylacetonate favors the oxygen storage in the lattice.

Enhancing electrocatalytic N2 conversion to NH3 by MnO2 ultralong nanowires with oxygen vacancies

2021 ◽  
Vol 02 ◽  
Author(s):  
Guangbin Wang ◽  
Renna Zhao ◽  
Fahao Ma ◽  
Zeyan Wang ◽  
Peng Wang ◽  
...  
Keyword(s):  
Active Sites ◽  
Manganese Oxides ◽  
Oxygen Vacancies ◽  
High Energy ◽  
Reduction Reaction ◽  
Ambient Conditions ◽  
Hydrogen Electrode ◽  
Faradaic Efficiency ◽  
Vacancy Defects ◽  
One Step

Background: At present, industrial synthesis of NH3 mainly relies on the Haber-Bosch process, which is characterized by harsh reaction conditions and high energy consumption. Electrochemical nitrogen reduction is considered to be a mild and sustainable alternative method for producing NH3, but efficient electrocatalyst under ambient conditions is the prerequisite for NH3 production. Objective: To demonstrate that CP@MnO2 ultralong nanowires is a highly-efficient electrocatalyst for N2 reduction reaction (NRR) under ambient conditions. Methods: The α-phase MnO2 synthesized by one-step hydrothermal method has an ultralong nanowires structure and oxygen vacancy defects. The catalysts was characterized by XRD, TEM, XPS, etc. The produced NH3 was estimated by indophenol blue method by UV-vis absorption spectra. Results: Such catalyst attains high Faradaic efficiency (FE) of 8.8% and a large NH3 yield of 1.13×10−10 mol cm−2 s−−1 at −0.7 V versus reversible hydrogen electrode in 0.1 M Na2SO4. In addition, the catalyst also shows high electrochemical stability and selectivity for NH3 formation. Conclusion: MnO2 ultralong nanowires can expose higher density of active sites and the spontaneously formed oxygen vacancies can manipulate the electronic structure of manganese oxides and provide coordination unsaturation sites (CUS) to enhance the adsorption of N2, which is the main reason for the high activity of the catalyst.

scholarly journals Spiers Memorial Lecture : Heterogeneous catalysis: understanding the fundamentals for catalyst design

2016 ◽  
Vol 188 ◽  
pp. 9-20
Author(s):  
Avelino Corma
Keyword(s):  
Active Sites ◽  
Catalyst Design ◽  
Memorial Lecture ◽  
Base Case ◽  
Synthesis Methods ◽  
Materials Synthesis ◽  
Chemoselective Hydrogenation ◽  
Isotopic Studies ◽  
Surface Active

Taking the chemoselective hydrogenation of substituted nitroaromatics as a base case, it will be shown that it is possible to design improved and new catalysts by attacking the problem in a multidisciplinary way. By combining molecular modeling with in situ operando spectroscopy, and with micro-kinetic and isotopic studies, it is possible to determine how and where on the catalysts the reactant molecules interact. Then, materials synthesis methods can be applied to prepare catalysts with the desired surface active sites and their selective interaction with the reactants.

Simultaneously adsorption, activation and in-situ reduction of carbon dioxide over Au loading BiOCl with rich oxygen vacancies

Nanoscale ◽  
2021 ◽  
Author(s):  
Yi-lei Li ◽  
Ying Liu ◽  
Hui-Ying Mu ◽  
Rui-hong Liu ◽  
ying-juan hao ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Main Process ◽  
In Situ Reduction ◽  
Co2 Photoreduction ◽  
Carbon Dioxide Co2

The main process of carbon dioxide (CO2) photoreduction is that the excited electrons are transported to the surfaced active sites to reduce the adsorbed CO2 molecules. Obviously, electron transfer to...

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

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