Photocatalytic Activity of Nanotubular TiO₂ Films Obtained by Anodic Oxidation: A Comparison in Gas and Liquid Phase

Influences of different carbon substrates on the morphologies of carbon/g-C3N4 photocatalytic composites and the purification capacities of different composites in the weak UV underwater environment

In order to explore the influence of various carbon introduction on the morphology and photodegradation performance of C/g-C₃N₄ composites, three kinds of different carbon materials: carbon nanotubes (CNT), graphene (GN) and carbon fibers (CF) were introduced to modify g-C₃N₄, and the morphologies, light absorption capacities and the underwater purifications of the composite photocatalysts were investigated. Results showed that the composites synthesized with different carbon substrates shows great differences in growth morphology. In addition, the introduction of various carbon sources also has a great impact on the physical and chemical properties of the composites. Compared with GN/g-C₃N₄ and CF/g-C₃N₄, CNT/g-C₃N₄ shows strong light absorption ability, especially in long-wavelength region (570-660 nm). To further study the difference of degradation ability of the composites in the underwater environment, the purification performance of modified g-C₃N₄ at different water depths were carried out. The results show that under 40 cm of water, where the light intensity and ultra violet spectral are seriously attenuated, the purification efficiency of CNT/g-C₃N₄ at 40 cm is 3.35 times than that of g-C₃N₄. This work provides insight in the design of highly efficient metal-free photocatalysts for the environmental remediation.

3D structured TiO2-based aerogel photocatalyst for the high-efficiency degradation of toluene gas

A 3D TiO2-based aerogel is prepared that improves the mass-transfer efficiency of the gas–solid reaction for the high-efficiency degradation of toluene gas.

Immobilized Nano-TiO2 Photocatalysts for the Degradation of Three Organic Dyes in Single and Multi-Dye Solutions

Heterogeneous photocatalysis with titanium dioxide (TiO2) is considered one of the most promising Advanced Oxidation Processes (AOPs). In order to solve issues related to catalyst recovery and possible agglomeration, which are typical of catalysts in nanoparticle form, self-organized nanotubular TiO2 films directly immobilized on a metal substrate can be produced through anodization. In this study, a nanotubular anodic oxide was tested in the degradation of three organic dyes, namely Direct Red 80, Methylene Blue, and Rhodamine B, in single, binary, and ternary mixtures, to simulate industrial effluents with the co-presence of multiple dyes. To better understand the dyes’ behavior and possible interaction effects, spectrophotometry was used to analyze the degradation of each dye in the mixture. The zero-crossing first-order derivative approach and double divisor ratio spectra derivative method were used for the analysis of binary and ternary mixtures, respectively, to overcome quantification problems due to spectra overlapping. The photocatalytic system demonstrated good efficiency, supporting the use of nanotubular TiO2 as a photocatalyst for dye mixtures. Moreover, the interaction among dyes can actually affect, both positively and negatively, photodegradation kinetics, posing an issue in understanding the actual efficiency of the purification process as a function of the effluent composition.

Electrochemical Engineering of Nanoporous Materials for Photocatalysis: Fundamentals, Advances, and Perspectives

Photocatalysis comprises a variety of light-driven processes in which solar energy is converted into green chemical energy to drive reactions such as water splitting for hydrogen energy generation, degradation of environmental pollutants, CO2 reduction and NH3 production. Electrochemically engineered nanoporous materials are attractive photocatalyst platforms for a plethora of applications due to their large effective surface area, highly controllable and tuneable light-harvesting capabilities, efficient charge carrier separation and enhanced diffusion of reactive species. Such tailor-made nanoporous substrates with rational chemical and structural designs provide new exciting opportunities to develop advanced optical semiconductor structures capable of performing precise and versatile control over light–matter interactions to harness electromagnetic waves with unprecedented high efficiency and selectivity for photocatalysis. This review introduces fundamental developments and recent advances of electrochemically engineered nanoporous materials and their application as platforms for photocatalysis, with a final prospective outlook about this dynamic field.

Diethylene Glycol-Assisted Organized TiO2 Nanostructures for Photocatalytic Wastewater Treatment Ceramic Membranes

A high-performance photocatalytic ceramic membrane was developed by direct growth of a TiO2 structure on a macroporous alumina support using a hydrothermal method. The morphological nanostructure of TiO2 on the support was successfully controlled via the interaction between the TiO2 precursor and a capping agent, diethylene glycol (DEG). The growth of anatase TiO2 nanorods was observed both on the membrane surface and pore walls. The well-organized nanorods TiO2 reduced the perturbation of the alumina support, thus controlling the hydrolysis rate of the TiO2 precursor and reducing membrane fouling. However, a decrease in the amount of the DEG capping agent significantly reduced membrane permeability, owing to the formation of nonporous clusters of TiO2 on the support. Distribution of the organized TiO2 nanorods on the support was very effective for the improvement of the organic removal efficiency and antifouling under ultraviolet illumination. The TiO2 nanostructure associated with the reactive crystalline phase, rather than the amount of layered TiO2 formed on the support, which was found to be the key to controlling photocatalytic membrane reactivity. These experimental findings would provide a new approach for the development of efficacious photocatalytic membranes with improved performance for wastewater treatment.

Special Issue: Novel Photoactive Materials

Photoactivity represents the ability of a material to activate when interacting with light. It can be declined in many ways, and several functionalities arising from this behavior of materials can be exploited, all leading to positive repercussions on our environment. There are several classes of effects of photoactivity, all of which have been deeply investigated in the last few decades, allowing researchers to develop more and more efficient materials and devices. The special issue “Novel Photoactive Materials” has been proposed as a means to present recent developments in the field; for this reason the articles included touch different aspects of photoactivity, from photocatalysis to photovoltaics to light emitting materials, as highlighted in this editorial.