Hierarchical Honeycomb Br-, N-Codoped TiO2 with Enhanced Visible-Light Photocatalytic H2 Production

Recent Progress of Ion-Modified TiO2 for Enhanced Photocatalytic Hydrogen Production

Harnessing solar energy to produce hydrogen through semiconductor-mediated photocatalytic water splitting is a promising avenue to address the challenges of energy scarcity and environmental degradation. Ever since Fujishima and Honda's groundbreaking work in photocatalytic water splitting, titanium dioxide (TiO2) has garnered significant interest as a semiconductor photocatalyst, prized for its non-toxicity, affordability, superior photocatalytic activity, and robust chemical stability. Nonetheless, the efficacy of solar energy conversion is hampered by TiO2's wide bandgap and the swift recombination of photogenerated carriers. In pursuit of enhancing TiO2's photocatalytic prowess, a panoply of modification techniques has been explored over recent years. This work provides an extensive review of the strategies employed to augment TiO2's performance in photocatalytic hydrogen production, with a special emphasis on foreign dopant incorporation. Firstly, we delve into metal doping as a key tactic to boost TiO2's capacity for efficient hydrogen generation via water splitting. We elaborate on the premise that metal doping introduces discrete energy states within TiO2's bandgap, thereby elevating its visible light photocatalytic activity. Following that, we evaluate the role of metal nanoparticles in modifying TiO2, hailed as one of the most effective strategies. Metal nanoparticles, serving as both photosensitizers and co-catalysts, display a pronounced affinity for visible light absorption and enhance the segregation and conveyance of photogenerated charge carriers, leading to remarkable photocatalytic outcomes. Furthermore, we consolidate perspectives on the nonmetal doping of TiO2, which tailors the material to harness visible light more efficiently and bolsters the separation and transfer of photogenerated carriers. The incorporation of various anions is summarized for their potential to propel TiO2's photocatalytic capabilities. This review aspires to compile contemporary insights on ion-doped TiO2, propelling the efficacy of photocatalytic hydrogen evolution and anticipating forthcoming advancements. Our work aims to furnish an informative scaffold for crafting advanced TiO2-based photocatalysts tailored for water-splitting applications.

Liquid Metal Interfacial Engineering Strategy to Synthesize All-Carbon-Linked Porous Aromatic Frameworks for the Cycloaddition of CO2 with Epoxides

This study explores the room-temperature synthesis of porous materials and the immobilization of CO2 without the use of metals. The porous aromatic frameworks synthesized at room temperature retain the important functional group structure, and the abundance of carbon-chlorine bonds creates an excellent environment for imidazole linkage. Consequently, a catalyst conducive to the cycloaddition of carbon dioxide is obtained. Hexachloro-p-xylene is explored as the precursor, and a catalyst conducive to carbon dioxide cycloaddition is obtained. The functionalized porous aromatic frameworks (PAF-280-I/B) possess a conversion of 99.6% with a selectivity of 98.9% toward styrene carbonate (SC). The findings of this study can help mitigate the impact of greenhouse gases and enable the production of organic compounds in the circular carbonate platform, turning waste into valuable resources.

Photocatalytic Applications of ReS2-Based Heterostructures

ReS2-based heterostructures, which involve the coupling of a narrow band-gap semiconductor ReS2 with other wide band-gap semiconductors, have shown promising performance in energy conversion and environmental pollution protection in recent years. This review focuses on the preparation methods, encompassing hydrothermal, chemical vapor deposition, and exfoliation techniques, as well as achievements in correlated applications of ReS2-based heterostructures, including type-I, type-II heterostructures, and Z-scheme heterostructures for hydrogen evolution, reduction of CO2, and degradation of pollutants. We believe that this review provides an overview of the most recent advances to guide further research and development of ReS2-based heterostructures for photocatalysis.

Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

In this study, the newly synthesized TiO₂ and N doped TiO₂ clusters were added to silica sol to synthesize N-TiO₂/SiO₂ composites via the sol-gel method. Afterwards, the prepared sols were applied by brushing on portland cement. Doping with nitrogen significantly increased the absorption of TiO₂ towards the visible region, thus, increasing the photocatalytic activity. SEM characterization of the treated samples showed that the clusters were distributed in form of aggregates on the samples' surface. The self-cleaning and air de-polluting performances were assessed through methylene blue degradation and the oxidation of nitrogen oxide, resulting in methylene blue (MB) removal of 85% and 78% after 60 min of irradiation for SN10TiO₂ and STiO₂, respectively. Regarding air de-pollution performance, the newly synthesized photocatalysts showed the ability of NOx reduction. However, their efficiency was somewhat lower, in which 23.81% of NO has been oxidized by the sample SN10TiO₂, while SP25 showed a total NO conversion of 38.98%. The powdered xerogels of the newly synthesized nanoparticles revealed high photocatalytic efficiency concerning NO oxidation, resulting in a higher performance compared to those obtained by the xerogel containing P25.

Morphology-Governed Performance of Multi-Dimensional Photocatalysts for Hydrogen Generation

In the past few decades, extensive studies have been performed to utilize the solar energy for photocatalytic water splitting; however, up to the present, the overall efficiencies reported in the literature are still unsatisfactory for commercialization. The crucial element of this challenging concept is the proper selection and design of photocatalytic material to enable significant extension of practical application perspectives. One of the important features in describing photocatalysts, although underestimated, is particle morphology. Accordingly, this review presents the advances achieved in the design of photocatalysts that are dedicated to hydrogen generation, with an emphasis on the particle morphology and its potential correlation with the overall reaction performance. The novel concept of this work—with the content presented in a clear and logical way—is based on the division into five parts according to dimensional arrangement groups of 0D, 1D, 2D, 3D, and combined systems. In this regard, it has been shown that the consideration of the discussed aspects, focusing on different types of particle morphology and their correlation with the system’s efficiency, could be a promising route for accelerating the development of photocatalytic materials oriented for solar-driven hydrogen generation. Finally, concluding remarks (additionally including the problems connected with experiments) and potential future directions of particle morphology-based design of photocatalysts for hydrogen production systems have been presented.

Noble-metal-free hexagonal wurtzite CdS nanoplates with exposed (110) and (112) crystal facets for efficient visible-light H2 production

Hexagonal wurtzite CdS has been regarded as one of the most promising semiconductors for photocatalysis.

Modified Nano-TiO2 Based Composites for Environmental Photocatalytic Applications

TiO2 probably plays the most important role in photocatalysis due to its excellent chemical and physical properties. However, the band gap of TiO2 corresponds to the Ultraviolet (UV) region, which is inactive under visible irradiation. At present, TiO2 has become activated in the visible light region by metal and nonmetal doping and the fabrication of composites. Recently, nano-TiO2 has attracted much attention due to its characteristics of larger specific surface area and more exposed surface active sites. nano-TiO2 has been obtained in many morphologies such as ultrathin nanosheets, nanotubes, and hollow nanospheres. This work focuses on the application of nano-TiO2 in efficient environmental photocatalysis such as hydrogen production, dye degradation, CO2 degradation, and nitrogen fixation, and discusses the methods to improve the activity of nano-TiO2 in the future.

One-pot Synthesis of β-acetamido-β-(phenyl) Propiophenone using ZnO/Carbon Nanocomposites

AIM AND OBJECTIVES

The focus of the present work is to synthesize ZnO/C composite using dextrose as carbon source by combustion method and study the comparative evaluation on one-pot synthesis of β-acetamido- β-(phenyl) propiophenone over ZnO nanoparticles and ZnO/C composite catalyst.

MATERIALS AND METHODS

The ZnO nanoparticles has been synthesized by sol-gel method using zinc nitrate and NaOH and ZnO/Carbon composites by combustion method using zinc nitrate and dextrose as carbon source. The resulting gel was placed in a preheated muffle furnace at 400oC. The solution boils and ignites with a flame. On cooling highly amorphous powder of ZnO/Carbon composite is obtained.

RESULTS

The XRD patterns reveal the hexagonal phase with Wurtzite structure and the nanocrystalline nature of the catalysts. The SEM image of ZnO/C composite showed that it contains spherical particles with an average size of 41 nm. The average particle size of the composite was around 60nm by DLS method. The catalytic activity of the ZnO/Carbon composites has been analyzed by one-pot four-component condensation of benzaldehyde, acetophenone, acetyl chloride and acetonitrile. The feed molar ratio of 1:1 (Bz:AP) and catalyst loading of 30 mol% is found to be the optimal condition for β-acetamido ketone conversion over ZnO/carbon composite.

CONCLUSION

The substantial catalytic activity of the synthesized ZnO/C composite materials was tested by one-pot four-component condensation of benzaldehyde (Bz), acetophenone (AP), acetyl chloride (AC) and acetonitrile (AN) which showed a high β-acetamido ketone conversion under the optimized reaction conditions. It has also been found that the catalyst is very stable and reusable.

TiO2/SrTiO3/g-C3N4 ternary heterojunction nanofibers: gradient energy band, cascade charge transfer, enhanced photocatalytic hydrogen evolution, and nitrogen fixation

TiO₂/SrTiO₃/g-C₃N₄ ternary heterojunction nanofibers with a cascade energy band alignment were designed and then fabricated by a combination of electrospinning technology and gas-solid reaction. Their photocurrent responses were 1.4 and 1.8 times higher while their transient photoluminescence lifetime were about 0.75 and 0.79 times shorter than those of TiO₂/g-C₃N₄ nanofibers and SrTiO₃/g-C₃N₄ nanofibers, respectively. The enhanced photocurrent response, decreased lifetime, and their dramatically decreased photoluminescence intensity clearly indicated that highly efficient cascade charge transfer and separation were achieved in the ternary nanofibers with the gradient energy band alignment compared with the corresponding traditional binary nanofibers noted above. When tested in photocatalytic reduction reactions of H₂ evolution and nitrogen fixation, the corresponding reaction rates under simulated sunlight irradiation values of 1304 μmol g^-1 h^-1 and 2192 μmol g^-1 h^-1 L^-1 were 2.1 and 1.9 times better than those of TiO₂/g-C₃N₄ nanofibers and 4.2 and 3.3 times better than those of SrTiO₃/g-C₃N₄ nanofibers, respectively. Furthermore, the photocatalytic activities of the TiO₂/SrTiO₃/g-C₃N₄ nanofibers had no significant decrease after several cycles, indicating that they possessed good structural stability properties. This work provides a new route to design and fabricate an efficient photocatalyst for photocatalytic reduction reactions.

Preparation of Highly Stable and Effective N-Doped TiO2@SiO2 Aerogel Catalyst for Degradation of Organic Pollutants by Visible Light Catalysis

To obtain high stable and effective TiO2 photocatalyst, nano-N-doped TiO2@SiO2 (TiO2−xNx@SiO2, 0 ≤ x ≤ 2) composite aerogels were synthesized by the sol-gel method combined with supercritical drying and direct oxidation process. The adsorption/photocatalytic degradation efficiency of TiO2−xNx@SiO2 aerogels was evaluated by the degradation of RhB in aqueous solution under visible light irradiation. The physiochemical properties of the aerogels were examined by XRD, FT-IR, TEM, SEM, TG/DTA, and BET methods. It was found that the specific surface areas of all TiO2−xNx@SiO2 samples exceeded 700 m2/g and exhibited a honeycomb porous structure with fine particulate morphology. Photocatalytic activity tests show that the 500-TiO2@SiO2 composite aerogel exhibits the best adsorption/photocatalytic degradation rate for RhB, which obtained about 80% of the degradation rate in 30 min under visible light and over 95% after 120 min. On the one hand, the SiO2 aerogels can significantly inhibit the phase transition of TiO2, and the nano TiO2 can be highly dispersed in the SiO2 aerogels; On the other hand, if the oxidation temperature is selected properly, the N-doped TiO2−xNx@SiO2 aerogel can be obtained by simple TiN@SiO2 aerogel oxidation.

N-Doped Yellow TiO2 Hollow Sphere-Mediated Visible-Light-Driven Efficient Esterification of Alcohol and N-Hydroxyimides to Active Esters

Herein we report a simple synthetic protocol for N-doped yellow TiO₂ (N-TiO₂ ) hollow spheres as an efficient visible-light-active photocatalyst using aqueous titanium peroxocarbonate complex (TPCC) solution as precursor and NH₄ OH. In the developed strategy, the ammonium ion of TPCC and NH₄ OH acts as nitrogen source and structure-directing agent. The synthesized N-TiO₂ hollow spheres are capable of promoting the synthesis of active esters of N-hydroxyimide and alcohol through simultaneous selective oxidation of alcohol to aldehyde followed by cross-dehydrogenative coupling (CDC) under ambient conditions upon irradiation of visible light. It is possible to develop a novel and cost-effective one-pot strategy for the synthesis of important esters and amides on gram scale using the developed strategy. The catalytic activity of N-TiO₂ hollow spheres is much superior to that of other reported N-TiO₂ samples as well as TiO₂ with varying morphology.

Fluorine and tin co-doping synergistically improves the photoelectrochemical water oxidation performance of TiO2 nanorod arrays by enhancing the ultraviolet light conversion efficiency

Fluorine and tin co-doped rutile TiO₂ nanorod arrays are grown on fluorine-doped tin oxide substrates by a hydrothermal process and are used as photoanodes to perform photoelectrochemical water oxidation. Fluorine and tin co-doping synergistically enhances the ultraviolet light conversion efficiency of the resulting TiO₂, which enables its photocurrent density of photoelectrochemical water oxidation to be more than four times that of the undoped samples. Such improvement in photoelectrochemical performance is attributed to changes in the electronic structure of the rutile TiO₂ due to fluorine and tin co-doping. It is found that introducing tin into the matrix of rutile TiO₂ can improve the charge separation efficiency because of the enhanced migration of photogenerated electrons from the conduction band of TiO₂ to that of SnO₂ that occurs at local sites, while fluorine doping can greatly reduce the recombination of the photogenerated electron-hole pairs due to the presence of the Ti³⁺ state that is produced to compensate for the charge difference between F^- ions and O^2- ions. It is envisaged that the fluorine and tin co-doped TiO₂ nanorod arrays described will provide valuable platforms for wide photocatalytic applications that are not merely limited to photoelectrochemical water oxidation.

Concept of Stagnant Capillarity Water in the Nanoporous SiO2@(Zn,Ni)(O,S) Nanocomposite Photocatalyst as a Strategy to Improve Hydrogen Evolution

(Zn,Ni)(O,S) nanoparticles were uniformly deposited on nanoporous SiO₂ spheres to form SiO₂@(Zn,Ni)(O,S) nanocomposites (NCs). To obtain optimum deposition of (Zn,Ni)(O,S) on the SiO₂ spheres for the hydrogen evolution reaction (HER), different amounts of 0.25, 0.5, 1, and 1.5 mmol zinc precursor for (Zn,Ni)(O,S) were deposited on SiO₂ to obtain different SiO₂@(Zn,Ni)(O,S) NCs. All the as-prepared catalysts were examined with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photocurrent response, photoluminescence spectral studies. Finally, the HER performance was evaluated with SiO₂@(Zn,Ni)(O,S). The best SiO₂@(Zn,Ni)(O,S)-0.5 surprisingly reached 41.1 mmol/gh for generating H₂, which was about a 840% increase as compared to that of the SiO₂ sphere-free one. The great improvement in the HER rate was due to the utilization of nanoporous SiO₂ spheres. The concept of stagnant capillarity water, adopted from the leaf vein system, was applied to explain the enhanced HER reaction.

A Review of Recent Applications of Ion Beam Techniques on Nanomaterial Surface Modification: Design of Nanostructures and Energy Harvesting

Nanomaterials have gained plenty of research interest because of their excellent performance, which is derived from their small size and special structure. In practical applications, to acquire nanomaterials with high performance, many methods have been used to modulate the structure and components of materials. To date, ion beam techniques have extensively been applied for modulating the performance of various nanomaterials. Energetic ion beams can modulate the surface morphology and chemical components of nanomaterials. In addition, ion beam techniques have also been used to fabricate nanomaterials, including 2D materials, nanoparticles, and nanowires. Compared with conventional methods, ion beam techniques, including ion implantation, ion irradiation, and focused ion beam, are all pure physical processes; these processes do not introduce any impurities into the target materials. In addition, ion beam techniques exhibit high controllability and repeatability. Here, recent progress in ion beam techniques for nanomaterial surface modification is systematically summarized and existing challenges and potential solutions are presented.

Distorted 1T-ReS2 Nanosheets Anchored on Porous TiO2 Nanofibers for Highly Enhanced Photocatalytic Hydrogen Production

Recently, loading TiO₂ with transition-metal disulfides (TMDs) to construct dual functional heterostructures has been widely researched as an effective strategy to improve the photocatalytic performance of a TiO₂ photocatalyst. For the TMD cocatalysts, the 2H-MoS₂ and 1T-MoS₂ have been widely studied and researched. However, they suffer from poor catalytic activity sites/low charge transfer ability and an unstable structure. In this regard, distorted 1T-phase TMDs with a stable structure are greatly fit for the cocatalyst due to their high charge transfer ability and rich catalytic sites on both the edge and basal plane. Therefore, it is highly desirable to develop distorted 1T-phase TMD/TiO₂ heterostructures with well-identified interfaces for highly enhanced photocatalytic performance. Herein, we first introduce distorted 1T-ReS₂ anchored on porous TiO₂ nanofibers as a promising photocatalyst for achieving an excellent photocatalytic hydrogen production. The excellent performance is attributed to the strong chemical interaction of the Ti-O-Re bond between TiO₂ and ReS₂, the excellent electron mobility of distorted 1T-ReS₂, and the abundant catalytic activity sites on both the plane and edge of the ReS₂ cocatalyst.

Highly Active Photocatalyst of Cu2O/TiO2 Octahedron for Hydrogen Generation

Heterojunction catalysts are attracting attention in the field of photocatalytic hydrogen generation for their effective light utilization and charge separation personalities. In this work, we report a simple and low-cost two-step solvothermal method for synthesizing Cu₂O/TiO₂ heterojunction catalysts with an octahedral morphology and a mean particle size of about 30 nm. It is found that the introduction of Cu₂O astonishingly enhances the photocatalytic performance of TiO₂. Under the condition of methanol acting as a sacrificial agent, the heterojunction with 0.19% Cu species shows an optimal hydrogen generation rate of 24.83 mmol g^-1 h^-1, which is nearly 3 orders of magnitude higher than that of the pristine TiO₂ catalyst.

Enhanced photoredox water splitting of Sb–N donor–acceptor pairs in TiO2

The development of noble-metal-free TiO₂-based catalysts is of significant interest for photoredox H₂ production.