C,N co-doped porous TiO2 hollow sphere visible light photocatalysts for efficient removal of highly toxic phenolic pollutants

C,N co-doped TiO2 hollow nanofibers coated stainless steel meshes for oil/water separation and visible light-driven degradation of pollutants

Complex pollutants are discharging and accumulating in rivers and oceans, requiring a coupled strategy to resolve pollutants efficiently. A novel method is proposed to treat multiple pollutants with C,N co-doped TiO₂ hollow nanofibers coated stainless steel meshes which can realize efficient oil/water separation and visible light-drove dyes photodegradation. The poly(divinylbenzene-co-vinylbenzene chloride), P(DVB-co-VBC), nanofibers are generated by precipitate cationic polymerization on the mesh framework, following with quaternization by triethylamine for N doping. Then, TiO₂ is coated on the polymeric nanofibers via in-situ sol-gel process of tetrabutyl titanate. The functional mesh coated with C,N co-doped TiO₂ hollow nanofibers is obtained after calcination under nitrogen atmosphere. The resultant mesh demonstrates superhydrophilic/underwater superoleophobic property which is promising in oil/water separation. More importantly, the C,N co-doped TiO₂ hollow nanofibers endow the mesh with high photodegradation ability to dyes under visible light. This work draws an affordable but high-performance multifunctional mesh for potential applications in wastewater treatment.

Fabrication of MOF-derived tubular In2O3@SnIn4S8 hybrid: Heterojunction formation and promoted photocatalytic reduction of Cr(VI) under visible light

Tubular In₂O₃@SnIn₄S₈ hierarchical hybrid photocatalyst was firstly fabricated by a two-step method. The morphology and composition were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The XRD results show that the obtained In₂O₃ microtubes were highly crystallized, while the SnIn₄S₈ flakes prepared at low temperature were poorly crystallized. The SEM image of the hybrid shows that numerous SnIn₄S₈ nanoflakes were assembled over the surface of In₂O₃ microtubes. In₂O₃ served as dispersing-templates have reduced the agglomeration of SnIn₄S₈ flakes. Meanwhile, the heterojunctions formed at the interfaces between In₂O₃ and SnIn₄S₈ could facilitate the interfacial charge transfer, as well as promote the photocatalytic activity of the hybrid. In the treatment of Cr(VI)-containing wastewater, the In₂O₃@SnIn₄S₈ hybrid not only exhibited strong adsorption ability, but also showed remarkably enhanced photocatalytic activity compared with pure SnIn₄S₈. The photocatalytic reaction constant k for In₂O₃@SnIn₄S₈ was approximately 2.54 times higher than that of SnIn₄S₈. The efficient activity of this hybrid photocatalyst should be ascribed to the promoted separation efficiency of electron/hole pairs, which was proved by the following three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs), photocurrent responds, and EIS characterizations.

C-,N- and S-Doped TiO2 Photocatalysts: A Review

This article presents an overview of the reports on the doping of TiO2 with carbon, nitrogen, and sulfur, including single, co-, and tri-doping. A comparison of the properties of the photocatalysts synthesized from various precursors of TiO2 and C, N, or S dopants is summarized. Selected methods of synthesis of the non-metal doped TiO2 are also described. Furthermore, the influence of the preparation conditions on the doping mode (interstitial or substitutional) with reference to various types of the modified TiO2 is summarized. The mechanisms of photocatalysis for the different modes of the non-metal doping are also discussed. Moreover, selected applications of the non-metal doped TiO2 photocatalysts are shown, including the removal of organic compounds from water/wastewater, air purification, production of hydrogen, lithium storage, inactivation of bacteria, or carbon dioxide reduction.

Effect of Calcination Time on the Physicochemical Properties and Photocatalytic Performance of Carbon and Nitrogen Co-Doped TiO2 Nanoparticles

The application of highly active nano catalysts in advanced oxidation processes (AOPs) improves the production of non-selective hydroxyl radicals and co-oxidants for complete remediation of polluted water. This study focused on the synthesis and characterisation of a highly active visible light C–N-co-doped TiO2 nano catalyst that we prepared via the sol-gel method and pyrolysed at 350 °C for 105 min in an inert atmosphere to prevent combustion of carbon moieties. Then we prolonged the pyrolysis holding time to 120 and 135 min and studied the effect of these changes on the crystal structure, particle size and morphology, electronic properties and photocatalytic performance. The physico-chemical characterisation proved that alteration of pyrolysis holding time allows control of the amount of carbon in the TiO2 catalyst causing variations in the band gap, particle size and morphology and induced changes in electronic properties. The C–N–TiO2 nano composites were active under both visible and UV light. Their improved activity was ascribed to a low electron–hole pair recombination rate that enhanced the generation of OH· and related oxidants for total deactivation of O.II dye. This study shows that subtle differences in catalyst preparation conditions affect its physico-chemical properties and catalytic efficiency under solar and UV light.

Impact of Titanium Dioxide (TiO2) Modification on Its Application to Pollution Treatment—A Review

A high-efficiency method to deal with pollutants must be found because environmental problems are becoming more serious. Photocatalytic oxidation technology as the environmentally-friendly treatment method can completely oxidate organic pollutants into pollution-free small-molecule inorganic substances without causing secondary pollution. As a widely used photocatalyst, titanium dioxide (TiO2) can greatly improve the degradation efficiency of pollutants, but several problems are noted in its practical application. TiO2 modified by different materials has received extensive attention in the field of photocatalysis because of its excellent physical and chemical properties compared with pure TiO2. In this review, we discuss the use of different materials for TiO2 modification, highlighting recent developments in the synthesis and application of TiO2 composites using different materials. Materials discussed in the article can be divided into nonmetallic and metallic. Mechanisms of how to improve catalytic performance of TiO2 after modification are discussed, and the future development of modified TiO2 is prospected.

pH-Controllable regeneration and visible-light photocatalytic redox of carbon and nitrogen co-doped Zn3Nb2O8 towards degradation of multiple contaminants

N/C–Zn₃Nb₂O₈ with a compatible band structure and negative surface demonstrates enhanced visible light photocatalytic activity and stability in degradation of multiple pH-sensitive contaminants.

Synthesis of pure and C/S/N co-doped Titania on Al mesh and their photocatalytic usage in Benzene degradation

Pure and co-doped Titania thin films were prepared on aluminum substrates through the sol-gel method. The co-doped sample showed higher photocatalytic activity on benzene degradation compared to pure TiO₂ under visible light illumination. XRD results showed the anatase phase for both TiO₂ and co-doped TiO₂ lattices with an average crystalline size of 12.9 and 10.4 nm, respectively. According to the UV-visible absorption spectra results, co-doped Titania showed higher visible light absorption compared to pure Titania. The synergistic effect of dopants caused a redshift to visible light absorption and also the lifetime of the photogenerated electron-hole were increased by induced electron levels in Titania lattice. The novelty of this study is the reactor's specific design. We employed Al mesh as thin film substrate for 3 main reasons, first, the large surface area of the Al mesh causes to increase specific surface area of the photocatalysts, also it is a formable substrate which can be engineered geometrically to decrease the shadow spots so the thin films will receive the highest light irradiation. Also, the Al mesh flexibility facilitates the procedure of reactor design to reach a minimum pressure drop of airflow while it is installed in the air conditioners or HVAC systems.

An ionic liquid functionalized polymer for simultaneous removal of four phenolic pollutants in real environmental samples

An ionic liquid functionalized polymer (IL-P) was prepared feasibly and simply by grafting1-butyl-3-vinylimidazolium bromide onto the silica surface. The IL-P was fully characterized, and the results showed that IL-P has a rough surface with a lower specific surface area (205.49 m² g^-1), and the involvement of ionic liquid significantly improved the adsorption performance of IL-P. The pH, initial concentration, adsorption time and temperature were investigated to discuss the adsorption behaviors of IL-P in aqueous solution. The adsorption process of 2,4-dichlorophenol (2,4-DCP), bisphenol A (BPA) and 2,4-dinitrophenol (2,4-DNP) onto IL-P better fitted the pseudo-second-order model, while that of 2-isonaphthol (2-NP) followed the pseudo-first-order model. The adsorption behaviors of IL-P towards 2,4-DCP and 2,4-DNP fitted well with Liu isotherm model, and that of BPA and 2-NP can be described by Langmuir model. The maximum adsorption capacities of 2,4-DCP, BPA, 2,4-DNP and 2-NP bound on IL-P was 239.7, 68.39, 56.86 and 64.28 mg g^-1, respectively, and the adsorption of IL-P is a spontaneous physical process. Comparing with other adsorbent, the as-prepared IL-P showed excellent recognition ability towards the phenolic compounds and can be applied to adsorb and remove trace 2,4-DCP, 2-NP, 2,4-DNP and BPA simultaneously in complicated wastewater and soil samples.

Three-Dimensional Decoupling Co-Catalyst from a Photoabsorbing Semiconductor as a New Strategy To Boost Photoelectrochemical Water Splitting

A cocatalyst is normally deposited on a photoabsorbing semiconductor (PAS) for photoelectrochemical (PEC) water splitting, but with drawbacks of limited loading, reduced light absorption, and tendency of charge recombination. To tackle these problems, a scheme of three-dimensional (3D) decoupling cocatalysts from the PAS with a pore-spanning crisscross conducting polymer host is proposed in this work. To demonstrate the concept, a facile method was developed for the in situ cogrowth of FeO _x nanoparticles and conducting polymer (CP) network in various PAS with different microstructures such as a TiO₂ nanorod array, WO₃ nanosheet array, and planar TiO₂ nanoparticle film, generating the bespoke photoanodes. The as-synthesized photoanodes exhibited a significantly enhanced PEC water splitting performance, which is clearly shown to arise from the improved light utilization, increased catalytic active sites, enhanced charge separation, and decreased electrochemical impedance of the photoelectrode. This 3D decoupling strategy is expected to open a promising direction for designing efficient PEC cells.