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126 results on '"Čapek, Libor"'

31. Partially Reduced Ni-NiO-TiO 2 Photocatalysts for Hydrogen Production from Methanol–Water Solution.

Author

Drobná, Helena, Meinhardová, Vendula, Dubnová, Lada, Kozumplíková, Kateřina, Reli, Martin, Kočí, Kamila, and Čapek, Libor

Subjects
PHOTOCATALYSTS, SOL-gel processes, OPTICAL properties, SURFACE area, PHOTOCATALYTIC oxidation, HYDROGEN production
Abstract

The study compares the photocatalytic behavior of TiO2, NiO-TiO2, and Ni-NiO-TiO2 photocatalysts in photocatalytic hydrogen production from methanol–water solution. TiO2 and NiO-TiO2 photocatalysts with theoretical NiO loading of 0.5, 1.0, and 3.0 wt. % of NiO were prepared by the sol–gel method. The Ni-NiO-TiO2 photocatalysts were prepared by partial reduction of NiO-TiO2 in hydrogen at 450 °C. The Ni-NiO-TiO2 photocatalysts showed significantly higher hydrogen production than the NiO-TiO2 photocatalysts. The structural, textural, redox, and optical properties of all of the prepared photocatalysts were studied by using XRD, SEM, N2- adsorption, XPS, H2-TPR, and DRS. Attention is focused on the contribution of Ni loading, the surface composition (Ni2+, the lattice O2− species, and OH groups), the distribution of Ni species (dispersed NiO species, crystalline NiO phase, and the metallic Ni0 species), oxygen vacancies, TiO2 modification, the TiO2 crystallite size, and the specific surface area. [ABSTRACT FROM AUTHOR]

Published
2023
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49. The effect of Zr loading in Zr/TiO2 prepared by pressurized hot water on its surface, morphological and photocatalytic properties.

Author

Lang, Jaroslav, Matějová, Lenka, Matěj, Zdeněk, Čapek, Libor, Martaus, Alexandr, and Kormunda, Martin

Abstract

Zr/TiO2 anatase photocatalysts with 0.5, 1, 2, 5 and 7.5 mol.% Zr were prepared using pressurized hot water crystallization and their photocatalytic activity was explored in acid orange 7 photodegradation. Parent TiO2 was also prepared and tested. From all tested photocatalysts, 2 mol.% Zr/TiO2 showed the highest photoactivity, and 7.5 mol.% Zr/TiO2 showed the lowest photoactivity. The poor photoactivity of 7.5 mol.% Zr/TiO2 can be explained by the amorphous ZrO2 present in the surface layer (~1–3 μm depth) of TiO2 anatase nanocrystallite agregates which changed the aggregate morphology and shielded the anatase nanocrystallite surface. The type and amount of defects (e.g., oxygen vacancies, lattice defects) did not effect the photoactivity of Zr/TiO2 in AO7 photodegradation. The addition of Zr to TiO2 significantly affects the photocatalyst morphology and the location where amorphous ZrO2 forms. The optimal Zr loading in TiO2 was determined to be 2 mol.%. Highlights: The type and amount of defects do no effect the Zr/TiO2 photoactivity. Amorphous ZrO2 in surface layer of TiO2 agregates shields the anatase nanocrystallites surface. Amorphous ZrO2 in surface layer of TiO2 agregates decreases the Zr/TiO2 anatase photoactivity Zr4+ dopation in TiO2 affects crucially photocatalyst morphology. 2 mol.% Zr/TiO2 shows the highest photoactivity in acid orange 7 degradation. [ABSTRACT FROM AUTHOR]

Published
2019
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50. Photocatalytic reduction of carbon dioxide over Cu/TiO2 photocatalysts.

Author

Tasbihi, Minoo, Schomäcker, Reinhard, Kočí, Kamila, Troppová, Ivana, Edelmannová, Miroslava, Reli, Martin, and Čapek, Libor

Subjects
WASTEWATER treatment, CARBON dioxide reduction, TITANIUM dioxide, METHANE, SOL-gel processes, PHOTOCATALYSIS
Abstract

The photocatalytic reduction of CO2 with H2O was investigated using Cu/TiO2 photocatalysts in aqueous solution. For this purpose, Cu/TiO2 photocatalysts (with 0.2, 0.9, 2, 4, and 6 wt.% of Cu) have been synthesized via sol-gel method. The photocatalysts were extensively characterized by means of inductively coupled plasma optical emission spectrometry (ICP-OES), N2 physisorption (BET), XRD, UV-vis DRS, FT-IR, Raman spectroscopy, TEM-EDX, and photoelectrochemical measurements. The as-prepared photocatalysts contain anatase as a major crystalline phase with a crystallite size around 13 nm. By increasing the amount of Cu, specific surface area and band gap energy decreased in addition to the formation of large agglomeration of CuO. Results revealed that the photocatalytic reduction of CO2 decreased in the presence of Cu/TiO2 in comparison to pure TiO2, which might be associated to the formation of CuO phase acting as a recombination center of generated electron-hole pair. Decreasing of photoactivity can also be connected with a very low position of conduction band of photocatalysts with high Cu content, which makes H2 production necessary for CO2 reduction more difficult. [ABSTRACT FROM AUTHOR]

Published
2018
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