Revealing the A‐Site Effect of Lead‐Free A3Sb2Br9 Perovskite in Photocatalytic C(sp3)−H Bond Activation

The lead‐free halide perovskite A₃Sb₂Br₉ is utilized as a photocatalyst for the first time for C(sp³)?H bond activation. A₃Sb₂Br₉ nanoparticles (A₃Sb₂Br₉ NPs) with different ratios of Cs and CH₃NH₃ (MA) show different photocatalytic activities for toluene oxidation and the photocatalytic performance is enhanced when increasing the amount of Cs. The octahedron distortion caused by A‐site cations can change the electronic properties of X‐site ions and further affect the electron transfer from toluene molecules to Br sites. After the regulation of A‐site cations, the photocatalytic activity is higher with A₃Sb₂Br₉ NPs than that with classic photocatalysts (TiO₂, WO₃, and CdS). The main active species involved in photocatalytic oxidation of toluene are photogenerated holes (h⁺) and superoxide anions (^.O₂^?). The octahedron distortion by A‐site cations affecting photocatalytic activity remains unique and is also a step forward for understanding more about halide‐perovskite‐based photocatalysis. The relationship between octahedron distortion and photocatalysis can also guide the design of new photocatalytic systems involving other halide perovskites.     

Revealing the A-Site Effect of Lead-Free A3Sb2Br9 Perovskite in Photocatalytic C(sp3)−H Bond Activation

The lead-free halide perovskite A₃Sb₂Br₉ is utilized as a photocatalyst for the first time for C(sp³)−H bond activation. A₃Sb₂Br₉ nanoparticles (A₃Sb₂Br₉ NPs) with different ratios of Cs and CH₃NH₃ (MA) show different photocatalytic activities for toluene oxidation and the photocatalytic performance is enhanced when increasing the amount of Cs. The octahedron distortion caused by A-site cations can change the electronic properties of X-site ions and further affect the electron transfer from toluene molecules to Br sites. After the regulation of A-site cations, the photocatalytic activity is higher with A₃Sb₂Br₉ NPs than that with classic photocatalysts (TiO₂, WO₃, and CdS). The main active species involved in photocatalytic oxidation of toluene are photogenerated holes (h⁺) and superoxide anions (^.O₂⁻). The octahedron distortion by A-site cations affecting photocatalytic activity remains unique and is also a step forward for understanding more about halide-perovskite-based photocatalysis. The relationship between octahedron distortion and photocatalysis can also guide the design of new photocatalytic systems involving other halide perovskites.     

Stable and Highly Efficient Photocatalysis with Lead‐Free Double‐Perovskite of Cs2AgBiBr6

Composition engineering of halide perovskite allows the tunability of the band gap over a wide range so that photons can be effectively harvested, an aspect that is of critical importance for increasing the efficiency of photocatalysis under sunlight. However, the poor stability and the low photocatalytic activity of halide perovskites prevent use of these defect‐tolerant materials in wide applications involving photocatalysis. Here, an alcohol‐based photocatalytic system for dye degradation demonstrated high stability through the use of double perovskite of Cs₂AgBiBr₆. The reaction rate on Cs₂AgBiBr₆ is comparable to that on CdS, a model inorganic semiconductor photocatalyst. The fact of fast reaction between free radicals and dye molecules indicates the unique catalytic properties of the Cs₂AgBiBr₆ surface. Deposition of metal clusters onto Cs₂AgBiBr₆ effectively enhances the photocatalytic activity. Although the stability (five consecutive photocatalytic cycles without obvious decrease of efficiency) requires further improvements, the results indicate the significant potential of Cs₂AgBiBr₆‐based photocatalysis.     

Bi2WO6/UiO-66复合材料的制备及其光催化性能

通过水热法制备了一种复合光催化剂Bi_2WO_6/UiO-66,探究了模板剂乙酸(CH_3COOH)对Ui O-66形貌的影响和2种中心元素Bi与Zr的不同物质的量之比对光催化性能的影响。通过XRD、SEM、N_2吸附-脱附、UV-Vis DRS、XPS等对催化剂的物相、形貌、比表面积、光吸收性能、元素组成等进行表征。实验结果表明,当n_(Bi)∶n_(Zr)=2∶1时,Bi_2WO_6/UiO-66对罗丹明B(RhB)的光催化活性最高,可见光照射50 min后,RhB的相对浓度降低98.5%。经过5次循环利用实验,催化剂的光催化活性没有明显下降,说明复合光催化剂的稳定性高。根据自由基捕获实验证明了空穴(h~+)为光催化中起决定性作用的活性物质,结合电化学测试以及UV-Vis DRS表征提出了可能的光催化降解机理。     

Hydrogenation and Ammoniation of SrTiO3 for an Enhanced Visible-light Photocatalysis

Hydrogenation and ammoniation of SrTiO₃ (STO), a normal ultraviolet photocatalyst, were performed by annealing STO〈100〉in H₂:N₂=5%:95% and NH₃, respectively, at various tem-peratures T. It was found that hydrogenation at T≥900 oC remarkably enhanced the UV photocatalytic ability of STO, but the visible-light photocatalysis was still unavailable, while ammoniation at T≥800 oC introduced the N doping, resulting in visible-light photocat-alytic activity. Furthermore, when a hydrogenated STO was subjected to ammoniation, the visible-light photocatalytic ability was nearly the same as that of the ammoniated one; but the hydrogenation of an ammoniated one significantly enhanced visible-light photocatalysis, indicating a synergetic effect of hydrogenation and ammoniation. Discussions and identifi-cations have been made to analyze these results.     

Cooperative Photocatalysis with 4-Amino-TEMPO for Selective Aerobic Oxidation of Amines over TiO2 Nanotubes

Attaching π-conjugated molecules onto TiO₂ can form surface complexes that could capture visible light. However, to make these TiO₂ surface complexes durable, integrating 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) or its analogues as a redox mediator with photocatalysis is the key to constructing selective chemical transformations. Herein, sodium 6,7-dihydroxynaphthalene-2-sulfonate (DHNS) was obtained by extending the π-conjugated system of catechol by adding a benzene ring and a substituent sodium sulfonate (−SO₃⁻Na⁺). The DHNS−TiO₂ showed the best photocatalytic activity towards the blue light-induced selective aerobic oxidation of benzylamine. Compared to TEMPO, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) could rise above 70% in conversion of benzylamine over the DHNS−TiO₂ photocatalyst. Eventually, a wide range of amines could be selectively oxidized into imines with atmospheric O₂ by cooperative photocatalysis of DHNS−TiO₂ with 4-amino-TEMPO. Notably, superoxide (O₂^•−) is crucial in coupling the photocatalytic cycle of DHNS−TiO₂ and the redox cycle of 4-amino-TEMPO. This work underscores the design of surface ligands for semiconductors and the selection of a redox mediator in visible light photocatalysis for selective chemical transformations.     

磷掺杂TiO2薄膜的制备与表征及其可见光照射下光催化降解邻苯二甲酸丁苄酯性能（英文）

P‐doped TiO2 (PTIO) thin‐films with different P contents were prepared using a sol‐gel method. The thin‐film samples were characterized using various techniques. The photocatalytic activity was evaluated by decomposing butyl benzyl phthalate under visible‐light irradiation. The results showed that the transformation of anatase to the rutile phase was inhibited and grain growth of TiO2 was prevented by P doping. The results confirm that the doped P atoms existed in two chemical forms, and those incorporated in the TiO2 lattice may play a positive role in photocatalysis. The high photocatalytic activities of the PTIO thin‐films may be the result of extrinsic absorption through the creation of oxygen vacancies, rather than excitation of the intrinsic absorption band of bulk TiO2 . The PTIO can be recycled with little depression of the photocatalytic activity. After six cycles, the photocatalytic activity of the PTIO film was still higher than 98%.     

具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe2O3@TiO2)

通过溶剂热和溶胶-凝胶涂层法, 设计并制备了具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe₂O₃@TiO₂). 透射电子显微镜(TEM)照片证明所得HP-Fe₂O₃@TiO₂样品具备分级多孔结构, 这是因为HP-Fe₂O₃@TiO₂的内核-Fe₂O₃具有大孔空隙, 同时外壳-TiO₂具有介孔空隙. 此外, 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)以及氮气吸附-脱附曲线深入研究了HP-Fe₂O₃@TiO₂的结构及其性质. 分别在可见及紫外光照下, 研究了样品在H₂O₂体系下的光催化降解亚甲基蓝(MB)的性质. 所观察到的HP-Fe₂O₃@TiO₂纳米球的光催化性能, 可归因于核-壳结构的协同作用, 这进一步表明, TiO₂外壳对α-Fe₂O₃的光催化活性有重要影响作用. 在可见光照射下, HP-Fe₂O₃@TiO₂ (1 mL Ti(OC₄H₉)₄ (TBT))具有较优异的光催化活性. 同时, HP-Fe₂O₃@TiO₂ (4mL TBT)具备优异的单分散形貌, 并在紫外光照射下, 表现出最优的光催化活性.     

Impact of synthesis methods on nanosized silver modified titania photocatalysts

This work reports the synthesis and studies on photocatalytic activity of a material based on titanium oxide doped with silver. Two kinds of Ag-deposited TiO₂ were synthesized via soft chemical reduction (SCR) and photodeposition (PD) methods. The structure, composition and chemical properties of the obtained products were investigated by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, photoluminescence spectra and Fourier transformation infrared spectroscopy techniques. The photocatalytic oxidation activity in a course of removal and destruction of organic compounds such as methyl orange dye using Ag/TiO₂ hybrid material was studied. The results suggest that SCR synthesized Ag/TiO₂ exhibited better photocatalytic performance that that obtained by PD method. The relationship between the synthesis method and photocatalytic activity of synthesized Ag/TiO₂ was analyzed with a focus on the plasmonic photocatalysis of silver. When compared to PD method, the SCR produced more homogeneous and smaller silver particles with a better dispersion than photodeposition that results in a relative increase of material activity in the photocatalytic degradation of dye pollutant.     

Cu2O cubic and polyhedral structures versus commercial powder: Shape effect on photocatalytic activity under visible light

A simple precipitation-reduction method was used to prepare cubic and polyhedral Cu₂O structures. Their morphological, structural, optical and electronic properties were analyzed and compared with those of commercial Cu₂O by means of SEM, TEM, XRD, UV–vis DRS, Photoluminescence Spectroscopy and Time Resolved Microwave Conductivity. Methyl orange (MO) photodegradation with visible light (blue-light LEDs, λ = 450–470 nm) was taken as a model reaction to study the photocatalytic activity. According to the results, Cu₂O edge-and corner-truncated polyhedral particles significantly decreased the MO initial concentration by adsorption and photocatalysis, whereas, Cu₂O cubic particles did not show MO adsorption but slightly higher photocatalytic activity than the polyhedral particles. Commercial Cu₂O showed MO adsorption and high electron mobility but it was completely inactive. These results were explained in terms of the crystalline defects that influence both, the adsorption capacity and the photocatalytic activity.     

Linker engineering in metal–organic frameworks for dark photocatalysis

Dark reactions featuring continuous activity under light off conditions play a critical role in natural photosynthesis. However, most artificial photocatalysts are inactive upon the removal of the light source, and the artificial photocatalysts with dark photocatalysis abilities have been rarely explored. Herein, we report a Ti-based metal–organic framework (MOF), MIL-125, exhibiting the capability of dark photocatalytic hydrogen production. Remarkably, the introduction of different functional groups onto the linkers enables distinctly different activities of the resulting MOFs (MIL-125-X, X = NH₂, NO₂, Br). Dynamic and thermodynamic investigations indicate that the production and lifetime of the Ti³⁺ intermediate are the key factors, due to the electron-donating/-withdrawing effect of the functional groups. As far as we know, this is the first report on dark photocatalysis over MOFs, providing new insights into the storage of irradiation energy and demonstrating their great potential in dark photocatalysis due to the great MOF diversity.

A Ti-based MOF with long-lived Ti³⁺ can achieve dark photocatalysis. The different groups on the organic linker modulate electron storage ability and the lifetime of Ti³⁺, significantly regulating dark photocatalytic activity in H₂ production.     

Investigation of Electron Behavior in Nano‐TiO2 Photocatalysis by Using In Situ Open‐Circuit Voltage and Photoconductivity Measurements

The in situ open‐circuit voltages (V_oc) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO₂ under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO₂ and from the methanol molecule. The electron injection from methanol to TiO₂ is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO₂ surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO₂ leads to the upshift of the Fermi level of electrons in TiO₂, which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano‐TiO₂ is continuously changing during photocatalysis as electrons are injected from methanol to TiO₂. Combined with the apparent Langmuir–Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO₂ CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of V_oc with time during photocatalysis.     

In Situ Corrosion Fabrication of NaNbO3/Nb3O7F Heterojunctions with Optimized Band Realignment for Enhanced Photocatalytic Hydrogen Evolution

Heterostructured photocatalysis is a significant issue owing to the unique band alignment, improved spectrum absorption, and enhanced photocatalytic activity. However, the construction of uniform, controllable, and effective heterojunctions is still a huge challenge. Herein, NaNbO₃/Nb₃O₇F heterojunctions are fabricated through an in situ corrosion technique for the first time. The influence of phase transformation on the hydrogen evolution reaction (HER) activity is investigated systematically in terms of photocatalytic water splitting for H₂ production. Interestingly, the band realignment and good interfacial contact endow the NaNbO₃/Nb₃O₇F heterojunctions with a high HER activity (43.3 mmol g⁻¹ h⁻¹), which is about 2.4 times that of pure Nb₃O₇F and 1.36 times that of pure NaNbO₃. The results may provide some new insights into the corrosion technique and HER activity of novel heterostructured catalysts.     

Preparation and photocatalytic activity of magnetic samarium-doped mesoporous titanium dioxide at the decomposition of methylene blue under visible light

Preparation of samarium-doped mesoporous titanium dioxide (Sm/MTiO₂) coated magnetite (Fe₃O₄) photocatalysts (Sm/MTiO₂/Fe₃O₄) and their activities under visible light were reported. The catalysts with Sm/MTiO₂ shell and a Fe₃O₄ core were prepared by coating photoactive Sm/MTiO₂ onto a magnetic Fe₃O₄ core through the hydrolysis of tetrabutyltitanate (Ti(OBu)₄, TBT) with precursors of Sm(NO₃)₃ and TBT in the presence of Fe₃O₄ nanoparticles. The morphological, structural and optical properties of the prepared samples were characterized by BET surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of Sm ion content on the photocatalytic activity was studied. The photocatalytic activities of obtained photocatalysts under visible light were estimated by measuring the decomposition rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Sm/MTiO₂ was tightly bound to Fe₃O₄ and could be easily recovered from the medium by a simple magnetic process. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.     

Heteroatom-Doped Ag25 Nanoclusters Encapsulated in Metal–Organic Frameworks for Photocatalytic Hydrogen Production

Atomically precise metal nanoclusters (NCs) with unique optical properties and abundant catalytic sites are promising in photocatalysis. However, their light-induced instability and the difficulty of utilizing the photogenerated carriers for photocatalysis pose significant challenges. Here, MAg₂₄ (M=Ag, Pd, Pt, and Au) NCs doped with diverse single heteroatoms have been encapsulated in a metal–organic framework (MOF), UiO-66-NH₂, affording MAg₂₄@UiO-66-NH₂. Strikingly, compared with Ag₂₅@UiO-66-NH₂, the MAg₂₄@UiO-66-NH₂ doped with heteroatom exhibits much enhanced activity in photocatalytic hydrogen production, among which AuAg₂₄@UiO-66-NH₂ presents the best activity up to 3.6 mmol g⁻¹ h⁻¹, far superior to all other counterparts. Moreover, they display excellent photocatalytic recyclability and stability. X-ray photoelectron spectroscopy and ultrafast transient absorption spectroscopy demonstrate that MAg₂₄ NCs encapsulated into the MOF create a favorable charge transfer pathway, similar to a Z-scheme heterojunction, when exposed to visible light. This promotes charge separation, along with optimized Ag electronic state, which are responsible for the superior activity in photocatalytic hydrogen production.     

水对甲醇在Rutile-TiO2(110)-(1 ×1)表面光催化解离的影响简

采用程序升温脱附方法研究了甲醇分子吸附在真空退火后的二氧化钛（110）表面的光催化过程,对比分析了单独吸附甲醇分子以及甲醇分子与水分子共吸附情况下的光催化解离过程. 结果表明,在二氧化钛（110）表面吸附的甲醇分子对共吸附水分子的光催化解离过程并没有直接的帮助作用. 共吸附状态下的水分子也同样没有影响到甲醇的光致解离过程,但是水分子的存在抑制了甲醇光解产物甲醛的光致脱附过程,同时促进了甲酸甲酯的形成.     

Enhancing the Photocatalytic Activity of Anatase TiO2 by Improving the Specific Facet‐Induced Spontaneous Separation of Photogenerated Electrons and Holes

Recently, it has been proven that directional flow of photogenerated charge carriers occurs on specific facets of TiO₂ nanocrystals. Herein, we demonstrate that the photocatalytic activity of anatase TiO₂ nanocrystals in both photoreduction and photooxidation processes can be enhanced by selectively depositing Pt nanoparticles on the {101} facets, which strengthens spontaneously surface‐induced separation between photogenerated electrons and holes in the photocatalysis process. An optimal ratio of the oxidative {001} facets to the reductive {101} facets exists with regard to the photocatalysis of the faceted TiO₂ nanocrystals, and this is crucial for balancing the recombination and redox reaction rates of photogenerated electrons and holes. The present work might help us gain deeper insight into the relation between the specific surface of semiconductor photocatalysts and their photocatalytic activities and provides us with a new route to design photocatalysts with high photocatalytic activity.     

TiO<Subscript>2</Subscript>/WO<Subscript>3</Subscript> photoanodes with enhanced photocatalytic activity for air treatment in a polymer electrolyte cell

The application of electrochemically enhanced photocatalysis in air treatment using a Nafion-based photoelectrochemical cell and TiO₂/WO₃ photoanodes for organic vapor photooxidation under both UV and visible light irradiation is briefly presented. In that direction, the obtained results regarding the preparation and characterization of the TiO₂/WO₃ photoanodes with enhanced photocatalytic activity are reviewed. Particular emphasis is given in the comparison of the photocatalytic behavior of bilayer TiO₂/WO₃ coatings, electrosynthesized on stainless steel mesh and powder C + mixed (WO₃ + TiO₂) photoanodes. The advantages of using a high surface area C + mixed (WO₃ + TiO₂) powder catalysts as photoanodes against their plain TiO₂ + C and WO₃ + C analogues are discussed.     

异质型BiOI/NaBiO3光催化剂的合成及其光催化性能

根据表面化学蚀刻原理采用加热冷凝回流的方法制备了一系列组成的异质结构BiOI/NaBiO₃光催化剂.利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见漫反射光谱(UV-Vis-DRS)等技术对其晶相结构、微观形貌和光吸收性能进行了表征.光催化实验表明,BiOI/NaBiO₃在可见光下可以有效降解罗丹明B(RhB),当BiOI与NaBiO₃的物质的量分数为一定值时,异质结构的光催化剂明显优于单一组分的光催化活性.通过加入不同的牺牲剂及荧光实验结果推测了该异质结构材料的光催化机理,并且分析了其光生载流子的传输方向及光催化过程的活性物种.研究表明,BiOI/NaBiO₃的催化活性增强主要归结为两者之间形成了有效的异质结构,其内建电场能够促进光生载流子的分离,同时光生空穴h⁺在光催化降解过程中是主要的活性物种.     

Visible light photocatalytic activity and Photoelectrochemical property of Fe-doped TiO<Subscript>2</Subscript> hollow spheres by sol–gel method

Fe-doped TiO₂ hollow spheres (Fe-THs) were synthesized by sol–gel process using carbon spheres as templates. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectrum (DRS), N₂ adsorption–desorption isotherms, Electron paramagnetic resonance (EPR) spectroscopy and Photoluminescence emission spectroscopy (PL). UV–vis spectra showed that Fe³⁺ doping could extend the absorption edge to the visible region. EPR spectra showed that Fe³⁺ was incorporated into the crystal lattice of TiO₂, which could inhibit the recombination of photo-induced electron–hole pairs and improve the photocatalytic activity. The photocatalytic activities of the prepared samples were evaluated for the degradation of dye Reactive Brilliant Red X-3B (C.I. reactive red 2) under visible light irradiation. The results indicated that Fe³⁺ doping sample showed the highest photocatalytic activity with an optimal doping concentration of 0.50 wt%. The recycle ability of the Fe-THs was also investigated. After 5 cycles, the degradation rate was still higher than 90%, decreased by only 6.36% compared to the first cycle. Moreover, in order to characterize the electron-transferring efficiency in the process of photocatalysis reaction, a photocurrent-time spectrum was examined by anodic photocurrent response.