Effect of Ag modification on TiO2 and melem/g-C3N4 composite on photocatalytic performances

Here, the comparison of two different semiconductor materials is demonstrated, TiO₂ and melem/g-C₃N₄ composites-modified with balls of approximately 5 nm Ag nanoparticles (NPs) as photocatalysts for the degradation of the model dye acid orange 7 (AO7). The melem molecule synthesized here is one of a series of organic compounds consisting of triazine ring compounds with a structure similar to that of melam and melamine. The photodegradation process of AO7 was carried out to examine all powder materials as a potential photocatalyst. Additionally, two different lamps of wavelengths 368 nm (UV light) and 420 nm (VIS light) were applied to compare the photodegradation tests. A new synthesis route for the acquisition of Ag NPs (Ag content 0.5, 1.0 and 2.5 wt%), based on a wet and low temperature method without the use of reducing reagents was proposed. The best photocatalytic performances under UV and VIS light were obtained for both, TiO₂ and melem/g-C₃N₄ materials (new synthesis route) modified with a very low Ag content-0.5 wt%. The photodegradation activities using UV lamp (3 h, 368 nm irradiation) for samples with 0.5 wt% of Ag: TiO₂ and melem/g-C₃N₄, in excess of 95 and 94%, respectively, were achieved. The highest photoactive materials melem/g-C₃N₄ with 0.5 and 1 wt% Ag revealed 98% of activity under the VIS lamp after 3 h long irradiation. Our work demonstrates a novel, environmentally acceptable, and cost-effective chemical strategy for preparation of photocatalysts suitable for degradation of organic contaminants in wastewater treatment.

Synergistic role of in-situ Zr-doping and cobalt oxide cocatalysts on photocatalytic bacterial inactivation and organic pollutants removal over template-free Fe2O3 nanorods

Herein, we synthesized in-situ Zr-doped Fe₂O₃ NRs photocatalyst by successive simple hydrothermal and air quenching methods. The synergistic roles of CoO_x (1 wt%) and Zr-doping on bacteria inactivation and model organic pollutants over Fe₂O₃ NRs photocatalyst were studied in detail. Initially, rod-like Zr ((0-8) %)-doped Fe₂O₃ NRs were produced via a hydrothermal method. CoO_x was loaded onto the Zr ((0-8) %)-doped Fe₂O₃ NRs) surface by a wet impregnation approach. The Zr-doping conditions and CoO_x loadings were judiciously optimized, and a highly photoactive CoO_x(1 wt%)/Zr(6%)-doped Fe₂O₃ NRs photocatalyst was developed. The CoO_x(1 wt%) loaded Zr(6%)-doped Fe₂O₃ NRs photocatalyst revealed 99.4% inactivation efficiency compared with (0, 4 and 8)% Zr-doped Fe₂O₃ NRs, respectively. After CoO_x(1 wt%)/Zr(6%)-doped Fe₂O₃ NRs photocatalyst treatment, Bio-TEM images of bacterial cells showed extensive morphological deviations in cell membranes, compared with the non-treated ones. Additionally, the optimum CoO_x(1 wt%)/Zr(6%)-doped Fe₂O₃ NRs photocatalyst exhibited 99.2% BPA and 98.3% orange II dye degradation after light radiation for 3 h. This work will provide a rapid method for the development of photostable catalyst materials for bacterial disinfection and organic degradation.

Au/MoS2/Ti3C2 composite catalyst for efficient photocatalytic hydrogen evolution

The Au/MoS₂/Ti₃C₂ composite catalyst has efficient photocatalytic hydrogen evolution performance.

Improved Microbial Electrolysis Cell Hydrogen Production by Hybridization with a TiO2 Nanotube Array Photoanode

A microbial electrolysis cell (MEC) consumes the chemical energy of organic material producing, in turn, hydrogen. This study presents a new hybrid MEC design with improved performance. An external TiO2 nanotube (TNT) array photoanode, fabricated by anodization of Ti foil, supplies photogenerated electrons to the MEC electrical circuit, significantly improving overall performance. The photogenerated electrons help to reduce electron depletion of the bioanode, and improve the proton reduction reaction at the cathode. Under simulated AM 1.5 illumination (100 mW cm−2) the 28 mL hybrid MEC exhibits a H2 evolution rate of 1434.268 ± 114.174 mmol m−3 h−1, a current density of 0.371 ± 0.000 mA cm−2 and power density of 1415.311 ± 23.937 mW m−2, that are respectively 30.76%, 34.4%, and 26.0% higher than a MEC under dark condition.

Porous TiO₂-Based Gas Sensors for Cyber Chemical Systems to Provide Security and Medical Diagnosis

Gas sensors play an important role in our life, providing control and security of technical processes, environment, transportation and healthcare. Consequently, the development of high performance gas sensor devices is the subject of intense research. TiO₂, with its excellent physical and chemical properties, is a very attractive material for the fabrication of chemical sensors. Meanwhile, the emerging technologies are focused on the fabrication of more flexible and smart systems for precise monitoring and diagnosis in real-time. The proposed cyber chemical systems in this paper are based on the integration of cyber elements with the chemical sensor devices. These systems may have a crucial effect on the environmental and industrial safety, control of carriage of dangerous goods and medicine. This review highlights the recent developments on fabrication of porous TiO₂-based chemical gas sensors for their application in cyber chemical system showing the convenience and feasibility of such a model to provide the security and to perform the diagnostics. The most of reports have demonstrated that the fabrication of doped, mixed and composite structures based on porous TiO₂ may drastically improve its sensing performance. In addition, each component has its unique effect on the sensing properties of material.

Black N/H-TiO2 Nanoplates with a Flower-Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

A facile two-step strategy was used to prepare black of hydrogenated/nitrogen-doped TiO₂ nanoplates (NHTA) with a flower-like hierarchical architecture. In situ nitriding and self-assembly was realized by hydrothermal synthesis using tripolycyanamide as a N source and as a structure-directing agent. After thorough characterization, it was found that the hydrogenation treatment did not damage the flower-like architecture but distorted the anatase crystal structure and significantly changed the band structure of NHTA owing to the increased concentration of oxygen vacancies, hydroxyl groups, and Ti³⁺ cations. Under AM 1.5 illumination, the photocatalytic H₂ evolution rate on the black NHTA was approximately 1500 μmol g^-1  h^-1 , which was much better than the N-doped TiO₂ nanoplates (≈690 μmol g^-1  h^-1 ). This improvement in the hydrogen evolution rate was attributed to a reduced bandgap, enhanced separation of the photogenerated charge carriers, and an increase in the surface-active sites.

Hydrothermal synthesis of a Ba and Mg co-doped Bi12GeO20 photocatalyst with enhanced visible light catalytic activity

(Ba, Mg)-codoped Bi₁₂GeO₂₀ was successfully synthesized through the one-step hydrothermal method, and the band gap was greatly narrowed.