ELECTRONIC STRUCTURE AND REACTIVITY OF TM-DOPED La1-xSrxCoO3 (TM = Ni, Fe) CATALYSTS

2002 ◽  
Vol 09 (01) ◽  
pp. 277-283 ◽  
Author(s):  
S. C. GRICE ◽  
W. R. FLAVELL ◽  
A. G. THOMAS ◽  
S. WARREN ◽  
P. G. MARR ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Defect Structure ◽  
Decomposition Reaction ◽  
Surface Reactivity ◽  
Local Defect ◽  
Water Binding ◽  
Crotyl Alcohol ◽  
Doped Materials ◽  
Electron Holes

The catalytic properties of LaCoO 3 in the oxidation of organic molecules in aqueous solution are explored as a function of doping with both Sr substitution for La and Fe and Ni substitution for Co. VUV photoemission is used to explore the surface reactivity of the ceramic catalysts in aqueous solution, using H 2 O as a probe molecule. These measurements are complemented by EXAFS and XANES measurements designed to probe the local defect structure and by GC measurements of catalytic activity in the aqueous epoxidation of crotyl alcohol. We relate the observed catalytic activity to the defect structure of the doped materials. In Ni-doped materials, oxygen vacancies appear to be the predominant defect, whereas in Fe-doped samples, electron holes are stabilised on Fe, leading to very different behaviour in oxidation. The surface reactivity to water is also influenced by the TM d electron count, with water binding more strongly to Fe-doped materials than to those containing Ni. The influence of these factors on the rate of the unwanted hydrogen peroxide decomposition reaction and hence on activity in epoxidation is discussed.

CATALYTIC ACTIVITY OF THE COBALT(II) ION WITH PHENYLALANINE COMPLEX IN THE DECOMPOSITION REACTION OF CUMENE HYDROPEROXIDE IN AQUEOUS SOLUTION

2020 ◽  
Vol 54 (2 (252)) ◽  
pp. 105-111
Author(s):  
G.S. Grigoryan
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Kinetic Study ◽  
Decay Rate ◽  
Arrhenius Equation ◽  
Cumene Hydroperoxide ◽  
Catalytic Decomposition ◽  
Decomposition Reaction ◽  
Effective Constant ◽  
Kinetic Expression

The formation of Cօ2+ : phenylalanine (Phe) 1:1 complex has been confirmed via kinetic study in aqueous solution at pH>7, which acts as a model catalyst for the decomposition of cumene hydroperoxide (ROOH) in Co2++Phe+ROOH+H2O system. The kinetic expression of a single catalytic decomposition reaction of ROOH under the influence of [CoPhe]+ complex, as well as the Arrhenius equation describing the temperature dependence of the effective constant Keff (=Kcat[Co2+]0[Phe]0) of ROOH decay rate in the temperature range from 323 to 343 K are brought out.

Decomposition of hydrogen peroxide on a two-component NiO-CdO catalyst and the effect of ionizing radiation on its catalytic properties

1979 ◽  
Vol 44 (4) ◽  
pp. 1015-1022 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Nickel Oxide ◽  
Catalytic Properties ◽  
Cadmium Oxide ◽  
Chemisorb Oxygen ◽  
Composition Region ◽  
Chemisorbed Oxygen ◽  
Two Component

The catalytic properties of two-component catalyst nickel oxide-cadmium oxide with the proportions of the components covering the whole composition region 0-100% were examined by studying the decomposition of hydrogen peroxide in aqueous solution on it. In the range 0-25 mol.% CdO, cadmium oxide is found to affect infavourably the ability of nickel oxide to chemisorb oxygen. The amount of the chemisorbed oxygen increases several times on gamma irradiation of the samples. The effect of cadmium oxide on the catalytic activity of the system shows up in fresh samples only indirectly via the changed amount of the oxygen chemisorbed. In older samples the initial catalytic activity of the system is changed, which can be explained based on the concept of bivalent catalytic centres in terms of the co-action of the catalytic centres of the two oxides, which are in equilibrium. The irradiation of the system under study speeds up the processes leading to the establishing of this equilibrium which is thermally very stable, and results in a substantial increase of the catalytic activity of the samples investigated.

Stimuli-responsive Janus mesoporous nanosheets towards robust interfacial emulsification and catalysis

2020 ◽  
Vol 7 (12) ◽  
pp. 3242-3249
Author(s):  
Jiangyan Yang ◽  
Jialin Wang ◽  
Yijiang Liu ◽  
Huaming Li ◽  
Zhiqun Lin
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Stimuli Responsive ◽  
Phase Type

Stimuli-responsive amphiphilic Janus mesoporous nanosheets with pH-triggered emulsification performance, switchable catalytic activity in aqueous solution and oil-phase-type-dependent catalytic activity at an emulsion interface were crafted.

Ionic conductivity, phase composition, and local defect structure of ZrO2-Gd2O3system solid solution crystals

2019 ◽  
Vol 23 (9) ◽  
pp. 2619-2626 ◽  
Author(s):  
Ekaterina A. Agarkova ◽  
Mikhail A. Borik ◽  
Tatiana V. Volkova ◽  
Alexey V. Kulebyakin ◽  
Irina E. Kuritsyna ◽  
...  
Keyword(s):  
Solid Solution ◽  
Phase Composition ◽  
Ionic Conductivity ◽  
Defect Structure ◽  
Local Defect

scholarly journals AuNPs-Based Thermoresponsive Nanoreactor as an Efficient Catalyst for the Reduction of 4-Nitrophenol

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 963
Author(s):  
Wei Liu ◽  
Xiaolian Zhu ◽  
Chengcheng Xu ◽  
Zhao Dai ◽  
Zhaohui Meng
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Phase Transformation ◽  
Catalytic Activity ◽  
Catalytic Efficiency ◽  
Environmental Pollutant ◽  
Temperature Sensitive ◽  
Efficient Catalyst ◽  
Catalytic Rate ◽  
Silica Core

A new AuNPs-based thermosensitive nanoreactor (SiO2@PMBA@Au@PNIPAM) was designed and prepared by stabilizing AuNPs in the layer of poly(N,N’-methylenebisacrylamide) (PMBA) and subsequent wrapping with the temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM) layer. The new nanoreactor exhibited high dispersibility and stability in aqueous solution and effectively prevented the aggregation of AuNPs caused by the phase transformation of PNIPAM. The XPS and ATR-FTIR results indicated that AuNPs could be well stabilized by PMBA due to the electron transfer between the N atoms of amide groups in the PMBA and Au atoms of AuNPs. The catalytic activity and thermoresponsive property of the new nanoreactor were invested by the reduction of the environmental pollutant, 4-nitrophenol (4-NP), with NaBH4 as a reductant. It exhibited a higher catalytic activity at 20 °C and 30 °C (below LCST of PNIPAM), but an inhibited catalytic activity at 40 °C (above LCST of PNIPAM). The PNIPAM layer played a switching role in controlling the catalytic rate by altering the reaction temperature. In addition, this nanoreactor showed an easily recyclable property due to the existence of a silica core and also preserved a rather high catalytic efficiency after 16 times of recycling.

scholarly journals Multi-Electron-Transfer Catalysts Needed for Artificial Photosynthesis

2012 ◽  
Vol 1387 ◽  
Author(s):  
James Vickers ◽  
Hongjin Lv ◽  
Petro F. Zhuk ◽  
Yurii V. Geletii ◽  
Craig L. Hill
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Electron Transfer ◽  
Catalytic Activity ◽  
Induction Period ◽  
Water Oxidation ◽  
Fuel Production ◽  
Oxygen Ligand ◽  
Visible Light Driven ◽  
Simple Kinetic Model

ABSTRACTWe report a study on catalytic water oxidation by cobalt in oxygen ligand environments because such systems are as promising as any in the water oxidation component of solar fuel production. We have re-examined the catalytic activity of Co(II) in aqueous solution using either [Ru(bpy)3]3+ as a stoichiometric oxidant or in visible-light-driven reactions with persulfate as a sacrificial electron acceptor. In both systems a distinctive induction period is observed. A simple kinetic model is proposed that describes the experimental data well. The presence of an induction period is explained by relatively slow formation of the true catalyst from aquacobalt(II).

The acid-catalysed hydrolysis of α-methylallyl acetate in aqueous solution

1968 ◽  
Vol 21 (7) ◽  
pp. 1727
Author(s):  
RA Fredlein ◽  
I Lauder
Keyword(s):  
Aqueous Solution ◽  
Reaction Products ◽  
Arrhenius Parameters ◽  
Crotyl Alcohol ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Tracer Experiments

The kinetics of the acid-catalysed hydrolysis of a-methylallyl acetate in aqueous solution have been studied over the range 30-100�. Oxygen-18 tracer experiments reveal the mechanism to be solely Aac2 and the Arrhenius parameters are consistent with this conclusion. Crotyl alcohol is observed in the reaction products. The formation of rearranged alcohol is explained by allylic isomerization of the α-methylallyl alcohol produced by the hydrolysis.

scholarly journals Annihilation of the Catalytic Activity in Butene Isomerization of Porous Vycor Glass by Washing with EDTA Aqueous Solution

1977 ◽  
Vol 50 (12) ◽  
pp. 3411-3412 ◽  
Author(s):  
Shoji Hirai ◽  
Akira Morikawa ◽  
Yoshio Ishinaga ◽  
Kiyoshi Otsuka ◽  
Yuji Wada
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Butene Isomerization

Defect Structure and Network Disorder in Boron Doped Amorphous Silicon

1991 ◽  
Vol 219 ◽  
Author(s):  
M. B. Schubert ◽  
G. Schumm ◽  
E. Lotter ◽  
K. Eberhardt ◽  
G. H. Bauer
Keyword(s):  
Hydrogen Bonding ◽  
Fermi Level ◽  
Amorphous Silicon ◽  
Defect Structure ◽  
Boron Concentration ◽  
Hole Transport ◽  
Local Defect ◽  
Band Tail ◽  
Boron Doped ◽  
Transport Path

ABSTRACTA series of boron doped a-Si:H films have been characterized by PDS, FTIR, Raman, and SIMS in order to evaluate the effects of boron incorporation on structural properties and hydrogen bonding. Doping by B2H6 or B(CH3)3 does not significantly enhance the overall disorder of the silicon network showing up in the TO-like Raman halfwidth whereas remarkable changes in local, defect related structures are evident from PDS. An analysis of the data suggests two bands of defects in the pseudogap at low boron concentration and only one band for higher concentration. To account for Fermi level positions, shifts of the hole transport path well into the valence band tail upon doping must be invoked.

The catalytic activity and defect structure of zinc chromate

1991 ◽  
Vol 8 (5-6) ◽  
pp. 385-389 ◽  
Author(s):  
R. A. Jackson ◽  
C. R. A. Catlow ◽  
J. M. Thomas
Keyword(s):  
Catalytic Activity ◽  
Defect Structure ◽  
Zinc Chromate
Sign in / Sign up

Export Citation Format

Share Document