Authored by Stefan Kartunov*
Abstract
This article analyzes the developments on the subject and draws conclusions for the study 1722/М - 2017 at the UZNIT of TU - Gabrovo BG. Most metals are highly chemically reactive, especially at nanoscale, without having properties that can be easily used with TiO2 composites. As such, most of the metals below will be considered metal oxides of precious metals. In addition, the most common oxide TiO2 will be discussed, as other oxides are probably unstable and thus do not form stable composites.
Keywords: Nanocomposites; Silicon structures; Titanium dioxide
Introduction
A detailed consideration of all precious metals is given in study 1722/М-2017 at the UZNIT of Technical University-Gabrovo and [1]. Only palladium, platinum, silver and gold are considered here.
Technical Requirements
The development of Pd/TiO2-based palladium composites on visible light radiation was studied by Mohapatra. TiO2 nanoparticles were synthesized by Ti foil anodization followed by PdCl2 functionalization and subsequent H2/Ar calcining to crystallize TiO2 and converting the Pd salt to pure Pd. The synthesized composite with optimized 1.25wt % Pd showed significant photocatalytic improvement compared to naked TiO2 nanotubes. A nitrogen-dosed Pd/ TiO2-active to the visible light composite is also prepared. Prepared TiO2 nanotube matrices through a three-stage anodization of Ti foil, followed by calcination and hydrothermal reduction of Pd-nanoparticles on the crystal TiO2 nanotubes in the presence of polyvinylpyrrolidone (PVP) and Na I allow for controlling the PVP-concentration and the hydrothermal reaction time. Figures 1a and 1b show a Scanning electron microscope (SEM)-image of a preconditioned nanotube matrix, and Figures 1c and 1d show the mass after hydrothermal deposition of Pd. Figure 1 shows a Tunnel elec tron microscope (TEM)-image of the nanotube with clearly placed Pd-nanoparticles. No such silicon matrix composites are known.
Photocatalytic production of Pt/TiO2 composites consistently shows increasing growth with the advancement of nanoscale synthesis and controllable/tunable properties of nanomaterials. These composites allow optimization of parameters such as morphology, crystalline phase, crystallinity, porosity and surface area, each of which can alter the photoactivity of the composition. Improving photocatalytic activity with the introduction of Pt is typically attributed to the formation of a Schottky barrier at the metal- TiO2 interface. This happens because the work function of Pt (~ 5,36-5,63 eV) is greater than that of TiO2 (~ 4,6-4,7 eV), so that electrons are transferred at Pt and holes Localized in TiO2 media to improve photocatalytic efficiency. In order to improve the Pt/TiO2 composites, steps have been taken to optimize the interaction between Pt and TiO2 from Kandiel, effectively effecting the surface area and crystal structure of TiO2 in the resulting Pt/TiO2 composite and demonstrating that although the large Area is useful, increasing crystallinity is preferential. Increasing photocatalytic activity is due to the reduction of site defects that act as charge recombination centers when crystallinity increases.
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