Investigation of Co3O4 and LaCoO3 interaction by performing N2O decomposition tests under Co3O4-CoO transition temperature

The research presented in this paper addresses the question: How does the addition of a small amount of LaCoO3 impact the activity of a Co3O4 catalyst? By testing such a catalyst in N2O decomposition under conditions at which the thermal decomposition of Co3O4 to CoO is possible, one gains unique insight into how the two phases interact. The activity of such a catalyst increases in the entire studied temperature range, unlike the activity of the undoped cobalt catalyst which is lower at 850 °C than at 800 °C due to the reduction of Co3O4 to CoO. XRD measurements showed that CoO was also the main cobalt oxide present in the Co3.5La catalyst after operating at 850 °C, as did the XPS measurements, but there was no drop of activity associated with this change. The influence of NO, O2 and H2O on the activity of the new catalyst, Co3.5La, was determined. Lack of positive effect of NO, a known oxygen scavenger, on the activity was noticed at all temperatures, showing that the effect of LaCoO3 is probably due to increased oxygen desorption. Temperature programed oxidation (TPO) tests showed that the beneficial effects of the presence of LaCoO3 on the activity of cobalt oxide at 850 °C were probably caused by enhanced diffusion of O2− anions through the entire catalyst, which facilitates desorption of oxygen molecules from the surface

Indium(II) chloride as a precursor in the synthesis of ternary (Ag–In–S) and quaternary (Ag–In–Zn–S) nanocrystals

A new indium precursor, namely, indium(II) chloride, was tested as a precursor in the synthesis of ternary Ag−In−S and quaternary Ag−In−Zn−S nanocrystals. This new precursor, being in fact a dimer of Cl2In−InCl2 chemical structure, is significantly more reactive than InCl3, typically used in the preparation of these types of nanocrystals. This was evidenced by carrying out comparative syntheses under the same reaction conditions using these two indium precursors in combination with the same silver (AgNO3) and zinc (zinc stearate) precursors. In particular, the use of indium(II) chloride in combination with low concentrations of the zinc precursor yielded spherical-shaped (D = 3.7−6.2 nm) Ag−In−Zn−S nanocrystals, whereas for higher concentrations of this precursor, rodlike nanoparticles (L = 9−10 nm) were obtained. In all cases, the resulting nanocrystals were enriched in indium (In/Ag = 1.5−10.3). Enhanced indium precursor conversion and formation of anisotropic, longitudinal nanoparticles were closely related to the presence of thiocarboxylic acid type of ligands in the reaction mixture. These ligands were generated in situ and subsequently bound to surfacial In(III) cations in the growing nanocrystals. The use of the new precursor of enhanced reactivity facilitated precise tuning of the photoluminescence color of the resulting nanocrystals in the spectral range from ca. 730 to 530 nm with photoluminescence quantum yield (PLQY) varying from 20 to 40%. The fabricated Ag−In−S and Ag−In−Zn−S nanocrystals exhibited the longest, reported to date, photoluminescence lifetimes of ∼9.4 and ∼1.4 μs, respectively. It was also demonstrated for the first time that ternary (Ag−In− S) and quaternary (Ag−In−Zn−S) nanocrystals could be applied as efficient photocatalysts, active under visible light (green) illumination, in the reaction of aldehydes reduction to alcohols

Silver-doped TiO2 prepared by microemulsion method: Surface properties, bio- and photoactivity

A series of Ag-TiO2 photocatalysts were obtained in microemulsion system (water/AOT/cyclohexane), using several Ag precursor amounts ranging from 1.5 to 8.5 mol.%. The photocatalysts’ characteristics by X-ray diffraction, STEM microscopy, UV–vis spectroscopy, X-ray photoelectron spectroscopy, BET methods showed that a sample with the highest photo- and bioactivity had anatase structure, about 90m2/g specific surface area, absorbed light over 400nm and contained 1.64 at.% of silver (0.30 at.% of Ag0 and 1.34 at.% of Ag2O) and about 13 at.% of carbon in the surface layer. The photocatalytic activity of the catalysts was estimated by measuring the decomposition rate of phenol in 0.21mM aqueous solution under visible and ultraviolet light irradiation. The bioactivity of silver-doped titanium dioxide nanocomposites was estimated using bacteria Escherichia coli and Staphylococcus aureus, yeast Saccharomyces cerevisiae and pathogenic fungi belonging to Candida family. All modified powders showed localized surface plasmonresonance (LSPR) in visible region with almost the same position of LSPR peaks indicating that similar sizes of silver, regardless of used amount of Ag, is deposited on titania particles during microemulsion method. STEM microscopy revealed that almost 50% of observed silver nanoparticles deposited at the TiO2 surface are in the range from 5 to 10 nm

Investigation of Co3O4 and LaCoO3 Interaction by Performing N2O Decomposition Tests under Co3O4-CoO Transition Temperature

The research presented in this paper addresses the question: How does the addition of a small amount of LaCoO3 impact the activity of a Co3O4 catalyst? By testing such a catalyst in N2O decomposition under conditions at which the thermal decomposition of Co3O4 to CoO is possible, one gains unique insight into how the two phases interact. The activity of such a catalyst increases in the entire studied temperature range, unlike the activity of the undoped cobalt catalyst which is lower at 850 °C than at 800 °C due to the reduction of Co3O4 to CoO. XRD measurements showed that CoO was also the main cobalt oxide present in the Co3.5La catalyst after operating at 850 °C, as did the XPS measurements, but there was no drop of activity associated with this change. The influence of NO, O2 and H2O on the activity of the new catalyst, Co3.5La, was determined. Lack of positive effect of NO, a known oxygen scavenger, on the activity was noticed at all temperatures, showing that the effect of LaCoO3 is probably due to increased oxygen desorption. Temperature programed oxidation (TPO) tests showed that the beneficial effects of the presence of LaCoO3 on the activity of cobalt oxide at 850 °C were probably caused by enhanced diffusion of O2− anions through the entire catalyst, which facilitates desorption of oxygen molecules from the surface

Structure and properties of C60-Pd films formed by electroreduction of C60 and palladium(II) acetate trimer: evidence for the presence of palladium nanoparticles

The compn., surface morphol., structure, and electrochem. properties of thin solid films of the polymer, C60-Pd, were studied by Raman spectroscopy, XPS, powder X-ray diffraction (XRD), and energy dispersive X-ray fluorescence (EDXRF) as well as being examd. by SEM (SEM), high resoln. transmission electron microscopy (HRTEM) with selective area diffraction (SAD) and by cyclic voltammetry (CV), resp. The C60-Pd films were deposited onto Au or Pt electrodes by electroreductive co-polymn. of C60 and the palladium(ii) acetate trimer, [Pd(ac)2]3, in a mixed acetonitrile-toluene (4:1, vol./vol.) soln. of 0.1 M tetra(n-butyl)ammonium perchlorate under multicyclic voltammetry or potentiostatic conditions. The structure and compn. of the C60-Pd films were dependent on the relative concn. of the polymer precursors, i.e., C60 and [Pd(ac)2]3, in the soln. for electropolymn. That is, in films grown in solns. with a high [Pd(ac)2]3:C60 ratio, (-C60-Pd-)n polymeric chains were sepd. by the Pd nanoclusters. These films were relatively smooth and uniform. In contrast, films electropolymd. in solns. with a low [Pd(ac)2]3:C60 ratio were rough, porous and much less uniform. The presence of the Pd nanoclusters in the C60-Pd film influenced the electrode processes of probing redox species dissolved in soln. That is, electro-oxidn. of an N,N,N',N'-tetramethyl-1,4-phenylenediamine (TMPDA) electrochem. redox probe was partially inhibited at the electrode coated by the C60-Pd film with a relatively low Pd nanocluster content. In contrast, electro-oxidn. of TMPDA was effectively mediated by the C60-Pd film contg. appreciable amts. of dispersed Pd nanoclusters