TiO2–SnO2 Nanocomposites: Effect of Acid–Base and Structural-Adsorption Properties on Photocatalytic Performance

Catalytic behavior of a ZnO/TiO2 composite in the synthesis of polycarbonate diol

ZnO/TiO2 catalysts with different ZnO contents have been prepared through equal volume impregnation method, characterized by XRD, SEM, Py-IR, ICP, XPS, NH3-TPD and N2 adsorption/desorption, and evaluated in the synthesis of polycarbonate diol (PCDL) through transesterification. The results showed that titanium zinc oxide formed in these catalysts, and the content of acidic sites varied with the ZnO content, and ZnO/TiO2 (10%) has the highest acid amount. The ZnO/TiO2 (20%) with medium acidic sites showed the highest catalytic activity. The synthesis process of polycarbonate glycol was also optimized. Under the optimal reaction conditions, the yield of PCDL was 72.5%, and the M n reached 4829 g mol-1 with a PDI of 1.6.

Synthesis and applications of TiO2/ZnO hybrid nanostructures by ZnO deposition on TiO2 nanotubes using electrochemical processes

In recent years, TiO2/ZnO hybrid nanostructures have been attracting the interest of the scientific community due to their excellent photoelectrochemical properties. The main advantage of TiO2/ZnO hybrid nanostructures over other photocatalysts based on semiconductor materials lies in their ability to form heterojunctions in which the valence and conduction bands of both semiconductors are intercalated. This factor produces a decrease in the band gap and the recombination rate and an increase in the light absorption range. The aim of this review is to perform a revision of the main methods to synthesise TiO2/ZnO hybrid nanostructures by ZnO deposition on TiO2 nanotubes using electrochemical processes. Electrochemical synthesis methods provide an easy, fast, and highly efficient route to carry out the synthesis of nanostructures such as nanowires, nanorods, nanotubes, etc. They allow us to control the stoichiometry, thickness and structure mainly by controlling the voltage, time, temperature, composition of the electrolyte, and concentration of monomers. In addition, a study of the most promising applications for TiO2/ZnO hybrid nanostructures has been carried out. In this review, the applications of dye-sensitised solar cell, photoelectrocatalytic degradation of organic compounds, photoelectrochemical water splitting, gas sensors, and lithium-ion batteries have been highlighted.

A review on TiO2/SnO2 heterostructures as a photocatalyst for the degradation of dyes and organic pollutants

Industrialization, civilization and human activities have all grown steadily in recent years. As a result, small and large industries discharge many organic pollutants into the environment and contribute to environmental pollution. These compounds are quite stable and challenging to break down over time, posing a long-term risk. The heterogeneous advanced oxidation processes technology has gained tremendous attention. It depends on the light-induced formation of e^-/h⁺ pairs, which combine with water and aqueous oxygen to generate highly reactive hydroxyl radicals that degrade the organic pollutants in a solution and convert them ultimately into non-toxic products. In this paper, the synergetic impact of TiO₂-SnO₂ coupling with other semiconductor materials and their photodegradation performance on toxic contaminants in an aqueous medium has been reviewed. In addition, multiple approaches for the synthesis of TiO₂-SnO₂ photocatalysts have been discussed. Among them, hydrothermal, sol-gel, electrospinning, precipitation and even their combination are extensively used to synthesize various forms of nanostructures. These techniques demonstrate better tunability for visible absorption, suppression of e^-/h⁺ pair recombination and enhanced e^-/h⁺ separation to improve photocatalytic performance. This paper also summarises the role of different operating factors such as catalyst loading, pH, pollutants variation concentration, various light sources and oxidizing agents on the photodegradation of organic pollutants.

Application of TiO2-Based Photocatalysts to Antibiotics Degradation: Cases of Sulfamethoxazole, Trimethoprim and Ciprofloxacin

The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more than once. Sulfamethoxazole, trimethoprim and ciprofloxacin are the most commonly detected antibiotics in water systems worldwide. The persistent and toxic nature of these antibiotics makes their elimination by conventional treatment methods at wastewater treatment plants almost impossible. The application of advanced oxidation processes and heterogeneous photocatalysis over TiO2-based materials is a promising solution. This highly efficient technology has the potential to be sustainable, cost-efficient and energy-efficient. A comprehensive review on the application of various TiO2-based photocatalysts for the degradation of sulfamethoxazole, trimethoprim and ciprofloxacin is focused on highlighting their photocatalytic performance under various reaction conditions (different amounts of pollutant and photocatalyst, pH, light source, reaction media, presence of inorganic ions, natural organic matter, oxidants). Mineralization efficiency and ecotoxicity of final products have been also considered. Further research needs have been presented based on the literature findings. Among them, design and development of highly efficient under sunlight, stable, recyclable and cost-effective TiO2-based materials; usage of real wastewaters for photocatalytic tests; and compulsory assessment of products ecotoxicity are the most important research tasks in order to meet requirements for industrial application.

Characterization of Commercial TiO2 P90 Modified with ZnO by the Impregnation Method

This article is devoted to TiO2/ZnO nanocomposites’ creation by modifying with the commercial TiO2/P90 product using the impregnation method and identifying the effect of the ZnO modifier on its adsorption, structural, photocatalytic, and electrical properties. The synthesized TiO2/ZnO nanocomposites were characterized by XRD, XRF, XPS, and low-temperature nitrogen adsorption-desorption methods. As a result, nanostructured TiO2/ZnO composites with the ZnO content of 2, 5, 10, and 15% were obtained. It was shown that the phase composition of TiO2/P90 does not change during the nanocomposite synthesis. XPS studies of TiO2/ZnO nanocomposites indicated the presence of Ti4+, Zn2+, O2−, and OH states on their surface, which is associated with TiO2, ZnO, and hydroxide ions. The nitrogen adsorption-desorption method showed that the commercial TiO2/P90 sample is nonporous, and all TiO2/ZnO nanocomposites are characterized by almost the same homogeneous mesoporous structure. Experimentally established sorption and photocatalytic properties depend on the specific surface area and electrostatic interaction with dyes. The effect of the ZnO modifier on I-V characteristics of the TiO2/P90 sample was revealed. The obtained experimental data showed that the TiO2/P90 sample contains one type of current carriers, and TiO2/2ZnO and TiO2/5ZnO nanocomposites are characterized by two types of current carriers.