Constructing SrTiO3–TiO2 Heterogeneous Hollow Multi‐shelled Structures for Enhanced Solar Water Splitting

Constructing hollow multi‐shelled structures (HoMSs) has a significant effect on promoting light absorption property of catalysts and enhancing their performance in solar energy conversion applications. A facile hydrothermal method is used to design the SrTiO₃?TiO₂ heterogeneous HoMSs by hydrothermal crystallization of SrTiO₃ on the surface of the TiO₂ HoMSs, which will realize a full coverage of SrTiO₃ on the TiO₂ surface and construct the SrTiO₃/TiO₂ junctions. The broccoli‐like SrTiO₃?TiO₂ heterogeneous HoMSs exhibited a fourfold higher overall water splitting performance of 10.6 μmol h^?1 for H₂ production and 5.1 μmol h^?1 for O₂ evolution than that of SrTiO₃ nanoparticles and the apparent quantum efficiency (AQE) of 8.6 % at 365 nm, which can be mainly attributed to 1) HoMS increased the light absorption ability of the constructed photocatalysts and 2) the SrTiO₃?TiO₂ junctions boosted the separation efficiency of the photogenerated charge carriers.     

A Self‐Healing Integrated All‐in‐One Zinc‐Ion Battery

The self‐healing of zinc‐ion batteries (ZIBs) will not only significantly improve the durability and extend the lifetime of devices, but also decrease electronic waste and economic cost. A poly(vinyl alcohol)/zinc trifluoromethanesulfonate (PVA/Zn(CF₃SO₃)₂) hydrogel electrolyte was fabricated by a facile freeze/thaw strategy. PVA/Zn(CF₃SO₃)₂ hydrogels possess excellent ionic conductivity and stable electrochemical performance. Such hydrogel electrolytes can autonomously self‐heal by hydrogen bonding without any external stimulus. All‐in‐one integrated ZIBs can be assembled by incorporating the cathode, separator, and anode into hydrogel matrix since the fabrication of PVA/Zn(CF₃SO₃)₂ hydrogel is a process of converting the liquid to quasi‐solid state. The ZIBs show an outstanding self‐healing and can recover electrochemical performance completely even after several cutting/healing cycles.     

TiO2表面氧空位对Rup2P/TiO2/ITO薄膜电极光致电荷转移的影响

采用改性的TiCl4水解法制备出三种不同表面性质的TiO2-X(X=5,10,20,X表示加入NaOH的浓度,单位为mo·lL-1)样品.利用(1,10-邻菲咯啉)2-2-(2-吡啶基)苯咪唑钌混配配合物(Rup2P)作为敏化剂,制备出Rup2P/TiO2-5/ITO(铟锡金属氧化物)、Rup2P/TiO2-10/ITO和Rup2P/TiO2-20/ITO表面敏化薄膜电极.测试结果表明三种薄膜电极的光电转换效率Rup2P/TiO2-10/ITO最高,Rup2P/TiO2-20/ITO次之,Rup2P/TiO2-5/ITO最低.利用吸收光谱、表面光电压(SP)谱、荧光光谱和表面光电流作用谱等分析了Rup2P和三种TiO2的能带结构和表面性质;利用光致循环伏安和表面光电流作用谱研究了三种Rup2P/TiO2-X/ITO薄膜电极的光致界面电荷转移过程.结果表明,在光致界面电荷转移过程中,TiO2层表面氧空位对Rup2P/TiO2-X/ITO薄膜电极光致电荷转移产生重要影响.并进一步讨论了Rup2P/TiO2-X/ITO薄膜电极的光电流产生机理.     

Direct Z‐Scheme Hetero‐phase Junction of Black/Red Phosphorus for Photocatalytic Water Splitting

Black phosphorus (BP) has recently drawn attention in photocatalysis for its optical properties. However, limited by the rapid recombination of photogenerated carriers, the use of BP for photocatalytic water splitting still remains a huge challenge. Herein, we prepare a black/red phosphorus (BP/RP) hetero‐phase junction photocatalyst by a wet‐chemistry method to promote the interfacial charge separation and thus achieve Z‐scheme photocatalytic water splitting without using sacrificial agents. The Z‐scheme mechanism was confirmed by time‐resolved transient absorption spectroscopy. This work provides a novel insight into the interface design of hetero‐phase junction with atomic precision.     

Light‐Driven Self‐Healing of Nanoparticle‐Based Metamolecules

Metamolecules and crystals consisting of nanoscale building blocks offer rich models to study colloidal chemistry, materials science, and photonics. Herein we demonstrate the self‐assembly of colloidal Ag nanoparticles into quasi‐one‐dimensional metamolecules with an intriguing self‐healing ability in a linearly polarized optical field. By investigating the spatial stability of the metamolecules, we found that the origin of self‐healing is the inhomogeneous interparticle electrodynamic interactions enhanced by the formation of unusual nanoparticle dimers, which minimize the free energy of the whole structure. The equilibrium configuration and self‐healing behavior can be further tuned by modifying the electrical double layers surrounding the nanoparticles. Our results reveal a unique route to build self‐healing colloidal structures assembled from simple metal nanoparticles. This approach could potentially lead to reconfigurable plasmonic devices for photonic and sensing applications.     

Light‐Induced Water Splitting Causes High‐Amplitude Oscillation of pH‐Sensitive Layer‐by‐Layer Assemblies on TiO2

We introduce a simple concept of a light induced pH change, followed by high amplitude manipulation of the mechanical properties of an adjacent polymer film. Irradiation of a titania surface is known to cause water splitting, and this can be used to reduce the environmental pH to pH 4. The mechanical modulus of an adjacent pH sensitive polymer film can thus be changed by more than an order of magnitude. The changes can be localized, maintained for hours and repeated without material destruction.     

多种纳米结构Fe掺杂TiO2光热耦合水分解制氢研究

氧空位是材料缺陷工程的重要组成. 基于光生氧空位的直接热利用, 实现纯水分解制氢的光热耦合实验, 被认为是太阳能综合利用的有效途径. 以多种制备方法合成的TiO₂纳米材料为基础, 研究了多种形貌纳米TiO₂及其Fe掺杂改性材料的光热耦合反应能力. 通过高分辨透射电子显微镜(HRTEM)、 X射线衍射(XRD)和电子顺磁共振(EPR)对晶体特征进行表征, 利用漫反射光谱(DRS)、 光致发光(PL)和三电极测试法表征了材料的性能, 并结合密度泛函理论(DFT)计算了产氢反应路径. 研究结果表明, 溶胶-凝胶法制备的纳米颗粒相比水热法制备的纳米片及纳米线, 体相内缺陷较多, 载流子强度高, 光热耦合产氢效果较差. Fe掺杂改性扩展了光响应, 增强了载流子分离和寿命, 降低了电子传输阻抗, 利于光反应过程中光生氧空位的形成, 克服了制氢反应中的关键能垒. 同时, 纳米材料中的缺陷促进了Fe离子的有效掺杂, Fe掺杂TiO₂纳米颗粒的光热耦合平均产氢量为9.73 μmol/g, 性能提升达13倍.     

Au/La2Ti2O7 Nanostructures Sensitized with Black Phosphorus for Plasmon‐Enhanced Photocatalytic Hydrogen Production in Visible and Near‐Infrared Light

Efficient utilization of solar energy is a high‐priority target and the search for suitable materials as photocatalysts that not only can harvest the broad wavelength of solar light, from UV to near‐infrared (NIR) region, but also can achieve high and efficient solar‐to‐hydrogen conversion is one of the most challenging missions. Herein, using Au/La₂Ti₂O₇ (BP‐Au/LTO) sensitized with black phosphorus (BP), a broadband solar response photocatalyst was designed and used as efficient photocatalyst for H₂ production. The optimum H₂ production rates of BP‐Au/LTO were about 0.74 and 0.30 mmol g⁻¹ h⁻¹ at wavelengths longer than 420 nm and 780 nm, respectively. The broad absorption of BP and plasmonic Au contribute to the enhanced photocatalytic activity in the visible and NIR light regions. Time‐resolved diffuse reflectance spectroscopy revealed efficient interfacial electron transfer from excited BP and Au to LTO which is in accordance with the observed high photoactivities.     

Brookite TiO2 Nanoparticle Films for Dye‐Sensitized Solar Cells

Brookite TiO₂ nanoparticles have been synthesized at low temperature by a soft solution growth method and have been used as building blocks to prepare pure brookite nanoparticle porous films. The film brookite structure was confirmed by XRD and Raman spectroscopy. By spectrophotometry, it was shown that the films had a direct band gap of 3.4 eV. After sensitization by the N719 dye, efficient cells have been produced. A best overall conversion efficiency of 5.97 %, without a scattering layer, was found for the larger TiO₂ starting nanoparticles. The cell open‐circuit voltage was improved compared with that of anatase cells and a lower electron diffusion coefficient was found in the photoanodes made of smaller brookite particles. Lanthanum‐doped brookite nanoparticle films were also studied. They showed a marked decreased in the amount of dye loading, and hence, the solar cells had a reduced current density that was not compensated for by the increased open‐circuit voltage of the cells.     

表面氟化TiO2空心光催化剂制备及其应用

Recently, extensive studies have been carried out to synthesize spherical microassemblies with hollow interiors and specific surface functionalizations, which usually exhibit fascinating enhanced or emerging properties and have promising applications in catalysis, photocatalysis, energy conversion and storage, biomedical applications, etc. With particular emphasis on the results obtained mainly by the authors' research group, this review provides a brief summary of the recent progress on the fabrication and potential photocatalytic applications of fluorinated TiO₂ porous hollow microspheres(F-TiO₂ PHMs). The synthesis strategies for F-TiO₂ PHMs include a simplified two-step templating method and template-free method based on the fluoride-mediated self-transformation(FMST) mechanism. Compared to the two-step templating method, the template formation, coating, and removal steps for the FMST method are programmatically proceeded in "black-box"-like one-pot reactions without additional manual steps. The four underlying steps involved in the fabrication of F-TiO₂ PHMs through the FMST pathway, nucleation, self-assembly, surface recrystallization, and self-transformation, are presented. By controlling these four steps in the FMST pathway, F-TiO₂ PHMs can be successfully fabricated with a high yield by a simple one-pot hydrothermal treatment. The multi-level microstructural characteristics(including the interior cavity and hierarchical porosity) and compositions of hollow TiO₂ microspheres as well as the primary building blocks can be well tailored. The unique superstructures of the F-TiO₂ PHM photocatalysts provide advantages for photocatalytic applications by improving the light harvesting, mass transfer, and membrane antifouling. In addition, the in situ-introduced surface fluorine species during the formation of F-TiO₂ PHMs provide significant surface fluorination effects, which are not only favorable for the adsorption and activation of reactant molecules, but also beneficial for surface trapping and interfacial transfer of photo-excited electrons and holes. Moreover, the porous hollow superstructures exhibit considerably better compatibility and tolerance to guest modifications, and thus the photocatalytic performances of F-TiO₂ PHMs can be increased by synergetic host and guest modifications, such as ion doping, group functionalization, and nanoparticle loading. The light-harvesting range and intensity can be increased, the charge recombination can be reduced, mass transfer and adsorption can be promoted, and the surface reactivity can be tuned by introducing specific surface functionalities or nanoparticular cocatalysts. Consequently, the entire photocatalytic process can be systematically modulated to optimize the overall photocatalytic performance. The as-prepared F-TiO₂ PHMs typically integrate the merits of interior cavity, hierarchical porosity, and surface fluorination and are open to synergetic host-guest modifications, which provides abundant compositional/structural parameters and specific physicochemical properties for systematically modulating the interconnected photocatalytic processes and promising potential photocatalytic applications.     

Visible Light Photocatalytic Activity of Pt/N‐TiO2 towards Enhanced H2 Production from Water Splitting

Present work mainly focuses on experimental investigation to improvement of hydrogen production by water photoelectrolysis. An experimental facility was designed and constructed for visible light photocatalysis. A series of N‐TiO₂ photocatalysts impregnated with platinum on the surface of N‐TiO₂ were prepared. Hydrogen production upon irradiating aqueous Pt/N‐TiO₂ suspension with visible light was investigated. The shift in excitation wavelength of TiO₂ was 380 nm improved the yield of hydrogen production by N‐TiO₂ and Pt/N‐TiO₂. We used a 400 W mercury arc lamp combined with a 400 nm cutoff filter eliminating all the wavelengths under 400 nm. Pt/N‐TiO₂ material was characterized with TPR, reflective UV/Visible spectroscopy and TEM. The best hydrogen production rate obtained for this setup for N/Ti = 10, 0.05 wt% Pt/N‐TiO₂, through water splitting was about 772 μmolh^?1g^?1.     

Three‐in‐One Oxygen Vacancies: Whole Visible‐Spectrum Absorption,Efficient Charge Separation,and Surface Site Activation for Robust CO2 Photoreduction

A facile and controllable in situ reduction strategy is used to create surface oxygen vacancies (OVs) on Aurivillius‐phase Sr₂Bi₂Nb₂TiO₁₂ nanosheets, which were prepared by a mineralizer‐assisted soft‐chemical method. Introduction of OVs on the surface of Sr₂Bi₂Nb₂TiO₁₂ extends photoresponse to cover the whole visible region and also tremendously promotes separation of photoinduced charge carriers. Adsorption and activation of CO₂ molecules on the surface of the catalyst are greatly enhanced. In the gas‐solid reaction system without co‐catalysts or sacrificial agents, OVs‐abundant Sr₂Bi₂Nb₂TiO₁₂ nanosheets show outstanding CO₂ photoreduction activity, producing CO with a rate of 17.11 μmol g^?1 h^?1, about 58 times higher than that of the bulk counterpart, surpassing most previously reported state‐of‐the‐art photocatalysts. Our study provides a three‐in‐one integrated solution to advance the performance of photocatalysts for solar‐energy conversion and generation of renewable energy.     

Preparation of Cr‐doped TiO2/SiO2 Photocatalysts and their Photocatalytic Properties

Cr‐doped TiO₂/SiO₂ nanostructured materials were prepared employing a layer‐by‐layer assemblym technique. TiO₂ colloids were synthesized by a sol‐gel method using TiCl₄ as a precursor. The experimental results showed that sphere‐type TiO₂ particles on SiO₂ exhibited uniform shape and a narrow size distribution. The amount of Ti (wt %) increased as a function of the number of the coating layers. The coatingv layers was composed of anatase titania nanocrystals at 550 °C. The onset of band‐gap transition for Crdoped TiO₂/SiO₂ showed a red shift compared with that for the undoped TiO₂/SiO₂. And the photocatalytic activity of Cr‐doped TiO₂/SiO₂ was higher than that of undoped sample.     

TiO2基光解水析氢非贵金属共催化剂的研究

利用太阳能光催化水解制氢是获得清洁、廉价、无污染的氢气最有前景的一种方式。这个过程主要包括三个步骤：太阳光的捕获,电荷分离与转移,催化质子还原产生氢气。其中,大量的研究工作主要集中在前两步,对于第三步的研究则相对较少。然而,共催化剂的引入可以有效促进光催化活性并提高氢气产生速率。共催化剂主要分为贵金属共催化剂和非贵金属共催化剂,其中,贵金属共催化剂有着较高的活性,但是其价格及来源限制了其实际应用,因此开发廉价高效的非贵金属共催化剂非常重要。本文对TiO₂基光解水析氢的非贵金属共催化剂（过渡金属单质及其复合物以及非金属碳基材料）进行了总结,详细讨论了不同共催化剂的作用机理,并对共催化剂的发展方向进行了合理展望。     

Biphasic Synergistic Gel Materials with Switchable Mechanics and Self‐Healing Capacity

A fabrication strategy for biphasic gels is reported, which incorporates high‐internal‐phase emulsions. Closely packed micro‐inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape‐memory performance because of the switchable micro‐ inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self‐healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials.