Synthesis and Enhanced Photocatalytic Activity of a Hierarchical Porous Flowerlike p–n Junction NiO/TiO2 Photocatalyst

Hierarchical flowerlike β‐Ni(OH)₂ superstructures composed of intermeshed nanoflakes are synthesized by hydrothermal treatment with a mixed solution of C₂H₄(NH₂)₂, NaOH, and Ni(NO₃)₂. The as‐prepared β‐Ni(OH)₂ superstructures could be easily changed into NiO superstructures without great morphology change by calcination at 400 °C for 5 h. Furthermore, the TiO₂ nanoparticles can be homogeneously deposited on the surface of NiO superstructures by dispersing β‐Ni(OH)₂ powders in Ti(OC₄H₉)₄–C₂H₅OH mixed solution and then vaporizing to remove the ethanol at 100 °C, and finally calcination at 400 °C for 5 h. The prepared NiO/TiO₂ p–n junction superstructures show much higher photocatalytic activity for photocatalytic degradation of p‐chlorophenol aqueous solution than conventional TiO₂ powders and NiO superstructures prepared under the same experimental conditions. An obvious enhancement in the photocatalytic activity can be related to several factors, including formation of hierarchical porous structures, dispersion of TiO₂ particles on the surface of NiO superstructures, and production of a p–n junction. Further results show that NiO/TiO₂ composite superstructures can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and re‐used, compared with conventional powder photocatalysts. After many recycling experiments for the photodegradation of p‐chlorophenol, the NiO/TiO₂ composite sample does not exhibit any great activity loss, confirming that NiO/TiO₂ sample is stable and not photocorroded.     

具有分级纳米结构的In2S3/CdIn2S4在可见光下催化苯甲胺的氧化偶联反应

采用以太阳光为能源、半导体材料为催化剂的催化体系将胺类化合物转化为相应的亚胺类化合物的方法是一种理想的有机合成手段.为了探索这类反应更温和的反应条件及更清晰的反应机理,本工作以NH₂-MIL-68（In）和硫脲为前驱体制备了In₂S₃分级纳米管,并进一步采用热离子交换的方法制备了In₂S₃/CdIn₂S₄纳米管复合材料.采用粉末X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、高分辨透射电子显微镜（HRTEM）、紫外-可见漫反射光谱（UV-vis DRS）、荧光光谱（PL）和电化学阻抗谱（EIS）等分析手段对催化剂的结构、形貌、光电性质等进行了表征.实验结果显示,In₂S₃和CdIn₂S₄间有效异质结降低了In₂S₃/CdIn₂S₄复合材料的光生载流子的复合效率,使In₂S₃/CdIn₂S₄具有较高的催化活性.催化剂的活性测试实验结果证明,In₂S₃和CdIn₂S₄间有效异质结和分级结构间的协同作用使In₂S₃/CdIn₂S₄纳米复合材料可作为一种有效的光催化剂催化氧化苯甲胺的偶联反应.活性物种捕获实验证明该反应是由光生空穴（h⁺）引发的.此外,此研究发现苯甲胺的氧化偶联反应同时可以在氧气或氮气条件下发生,打破了该反应必须要有氧气参与的束缚,拓展了苯甲胺氧化偶联反应的适用范围.循环实验结果显示,催化剂可循环使用五次,证明该催化剂具有较好的稳定性.     

Plasmon‐Assisted Water Splitting Using Two Sides of the Same SrTiO3 Single‐Crystal Substrate: Conversion of Visible Light to Chemical Energy

A plasmon‐induced water splitting system that operates under irradiation by visible light was successfully developed; the system is based on the use of both sides of the same strontium titanate (SrTiO₃) single‐crystal substrate. The water splitting system contains two solution chambers to separate hydrogen (H₂) and oxygen (O₂). To promote water splitting, a chemical bias was applied by regulating the pH values of the chambers. The quantity of H₂ evolved from the surface of platinum, which was used as a reduction co‐catalyst, was twice the quantity of O₂ evolved from an Au‐nanostructured surface. Thus, the stoichiometric evolution of H₂ and O₂ was clearly demonstrated. The hydrogen‐evolution action spectrum closely corresponds to the plasmon resonance spectrum, indicating that the plasmon‐induced charge separation at the Au/SrTiO₃ interface promotes water oxidation and the subsequent reduction of a proton on the backside of the SrTiO₃ substrate. The chemical bias is significantly reduced by plasmonic effects, which indicates the possibility of constructing an artificial photosynthesis system with low energy consumption.     

Outside‐In Recrystallization of ZnS–Cu1.8S Hollow Spheres with Interdispersed Lattices for Enhanced Visible Light Solar Hydrogen Generation

For the first time an earth‐abundant and nontoxic ZnS–Cu_1.8S hybrid photocatalyst has been engineered with well‐defined nanosheet hollow structures by a template‐engaged method. In contrast to conventional surface coupling and loading, the unique outside‐in recrystallization promotes co‐precipitation of ZnS and Cu_1.8S into homogeneous interdispersed lattices, hence forming a hybrid semiconductor with visible responsive photocatalytic activity. The as‐derived ZnS–Cu_1.8S semiconductor alloy is tailored into a hierarchical hollow structure to provide readily accessible porous shells and interior spaces for effective ion transfer/exchange. Notably, this synergistic morphology, interface and crystal lattice engineering, aim towards the design of novel nanocatalysts for various sustainable environmental and energy applications.     

Self‐Assembling of Er2O3–TiO2 Mixed Oxide Nanoplatelets by a Template‐Free Solvothermal Route

An easy solvothermal route has been developed to synthesize the first mesoporous Er₂O₃–TiO₂ mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er₂O₃–TiO₂ mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template‐free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313 m² g^?1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol–gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers.     

Modular Thiol–Ene Chemistry Approach towards Mesoporous Silica Monoliths with Organically Modified Pore Walls

The surface modification of mesoporous silica monoliths through thiol–ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol–gel hydrolysis–polycondensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3‐mercaptopropyl)trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore‐wall chemistries. Nitrogen sorption, small‐angle X‐ray scattering, solid‐state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore‐wall functionalization. This report demonstrates that thiol–ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces.     

Enhanced Ethylene Photodegradation Performance of g‐C3N4–Ag3PO4 Composites with Direct Z‐Scheme Configuration

Photocatalytic oxidation of ethylene continues to be a challenge at the frontier of chemistry. In a previous report, a simple Ag₃PO₄ semiconductor material was shown to have strong photooxidative properties and efficiently oxidised water and decomposed organics in aqueous solution under visible‐light illumination. Herein, its effects on the photo‐oxidation of gaseous C₂H₄ were investigated by fabricating graphitic C₃N₄–Ag₃PO₄ composite semiconductors with direct Z‐scheme configuration. It was found that both the ethylene photo‐oxidative activity and the stability of Ag₃PO₄ are considerably improved by fabrication of Z‐scheme composites. Moreover, stable C₂H₄ photo‐oxidation activity could be obtained by treating the composite at 450 °C for 3 h after long‐term operation. From the point of view of environmental pollutant cleanup, the present technique avoids the side reaction of oxidising water and will be valuable for further investigations on both Ag₃PO₄ and CH degradation.     

Color‐Controlled Ag Nanoparticles and Nanorods within Confined Mesopores: Microwave‐Assisted Rapid Synthesis and Application in Plasmonic Catalysis under Visible‐Light Irradiation

Color‐controlled spherical Ag nanoparticles (NPs) and nanorods, with features that originate from their particle sizes and morphologies, can be synthesized within the mesoporous structure of SBA‐15 by the rapid and uniform microwave (MW)‐assisted alcohol reduction method in the absence or presence of surface‐modifying organic ligands. The obtained several Ag catalysts exhibit different catalytic activities in the H₂ production from ammonia borane (NH₃BH₃, AB) under dark conditions, and higher catalytic activity is observed by smaller yellow Ag NPs in spherical form. The catalytic activities are specifically enhanced under the light irradiation for all Ag catalysts. In particular, under light irradiation, the blue Ag nanorod shows a maximum enhancement of more than twice that observed in the dark. It should be noted that the order of increasing catalytic performance is in close agreement with the order of absorption intensity owing to the Ag localized surface plasmon resonance (LSPR) at irradiation light wavelength. Upon consideration of infrared thermal effect, wavelength dependence on catalytic activity, and effect of radical scavengers, it can be concluded that the dehydrogenation of AB is promoted by change of charge density of the Ag NP surface derived from LSPR. The LSPR‐enhanced catalytic activity can be further realized in the tandem reaction consisting of dehydrogenation of AB and hydrogenation of 4‐nitrophenol, in which a similar tendency in the enhancement of catalytic activity is observed.     

Direct Synthesis of a Photoactive Inorganic–Organic Mesostructured Hybrid Material and its Application as a Photocatalyst

A direct route : Silylated triphenylmethanol is incorporated into mesoporous material MCM‐41 through a direct synthesis method. Under acidic conditions, this inorganic–organic hybrid generates trityl cations to give the photoactive material Tyl‐MCM41. Tyl‐MCM41 promotes the photosensitized dimerization of 1,3‐cyclohexadiene with an unprecedented selectivity towards the formation of the exo product (see scheme).

     

TiO2 Nanotube Arrays Modified with Cr‐Doped SrTiO3 Nanocubes for Highly Efficient Hydrogen Evolution under Visible Light

In recent decades, solar‐driven hydrogen production over semiconductors has attracted tremendous interest owing to the global energy and environmental crisis. Among various semiconductor materials, TiO₂ exhibits outstanding photocatalytic properties and has been extensively applied in diverse photocatalytic and photoelectric systems. However, two major drawbacks limit practical applications, namely, high charge‐recombination rate and poor visible‐light utilization. In this work, heterostructured TiO₂ nanotube arrays grafted with Cr‐doped SrTiO₃ nanocubes were fabricated by simply controlling the kinetics of hydrothermal reactions. It was found that coupling TiO₂ nanotube arrays with regular SrTiO₃ nanocubes can significantly improve the charge separation. Meanwhile, doping Cr cations into SrTiO₃ nanocubes proved to be an effective and feasible approach to enhance remarkably the visible‐light response, which was also confirmed by theoretical calculations. As a result, the rate of photoelectrochemical hydrogen evolution of these novel heteronanostructures is an order of magnitude larger than those of TiO₂ nanotube arrays and other previously reported SrTiO₃/TiO₂ nanocomposites under visible‐light irradiation. Furthermore, the as‐prepared Cr‐doped SrTiO₃/TiO₂ heterostructures exhibit excellent durability and stability, which are favorable for practical hydrogen production and photoelectric nanodevices.     

Nickel Hydroxide Supercapacitor with a Theoretical Capacitance and High Rate Capability Based on Hollow Dendritic 3D‐Nickel Current Collectors

A straightforward way to attain the theoretical capacitance and high rate capability of nickel hydroxide supercapacitors, by utilizing a mesoporous hollow dendritic three‐dimensional‐nickel (3D‐Ni) current collector is proposed. A facile electrodeposition method employing a hydrogen bubble template was chosen for rapid fabrication of the dendritic 3D‐nickel structure. After nickel hydroxide was deposited on the hollow 3D‐nickel current collector, it exhibited a highest capacitance of 3637 F g⁻¹ at a current density of 1 A g⁻¹, and retained 97 % of capacitance at a high current density of 100 A g⁻¹ with a cycle stability of over 80 % after 10 000 cycles. The enhanced performance could be attributed to the large surface area and high conductivity of the moss‐like dendritic 3D‐Ni current collector, which allowed direct contact between the active materials and the current collector, and reduced diffusion resistance between the surface of the active materials and the electrolyte. These results not only confirmed a facile fabrication method for high‐performance 3D metal nanostructures, but also offer a promising solution for state‐of‐the‐art energy storage systems.     

Efficient Noble‐Metal‐Free γ‐Fe2O3@NiO Core–Shell Nanostructured Photocatalysts for Water Oxidation

Flowerlike noble‐metal‐free γ‐Fe₂O₃@NiO core–shell hierarchical nanostructures have been fabricated and examined as a catalyst in the photocatalytic oxidation of water with [Ru(bpy)₃](ClO₄)₂ as a photosensitizer and Na₂S₂O₈ as a sacrificial electron acceptor. An apparent TOF of 0.29 μmols^?1 m^?2 and oxygen yield of 51 % were obtained with γ‐Fe₂O₃@NiO. The γ‐Fe₂O₃@NiO core–shell hierarchical nanostructures could be easily separated from the reaction solution whilst maintaining excellent water‐oxidation activity in the fourth and fifth runs. The surface conditions of γ‐Fe₂O₃@NiO also remained unchanged after the photocatalytic reaction, as confirmed by X‐ray photoelectron spectroscopy (XPS).     

Hierarchical Fe3O4@TiO2 Yolk–Shell Microspheres with Enhanced Microwave‐Absorption Properties

A facile and efficient strategy for the synthesis of hierarchical yolk–shell microspheres with magnetic Fe₃O₄ cores and dielectric TiO₂ shells has been developed. Various Fe₃O₄@TiO₂ yolk–shell microspheres with different core sizes, interstitial void volumes, and shell thicknesses have been successfully synthesized by controlling the synthetic parameters. Moreover, the microwave absorption properties of these yolk–shell microspheres, such as the complex permittivity and permeability, were investigated. The electromagnetic data demonstrate that the as‐synthesized Fe₃O₄@TiO₂ yolk–shell microspheres exhibit significantly enhanced microwave absorption properties compared with pure Fe₃O₄ and our previously reported Fe₃O₄@TiO₂ core–shell microspheres, which may result from the unique yolk–shell structure with a large surface area and high porosity, as well as synergistic effects between the functional Fe₃O₄ cores and TiO₂ shells.