TiO2 Nanotubes: Nitrogen‐Ion Implantation at Low Dose Provides Noble‐Metal‐Free Photocatalytic H2‐Evolution Activity

Low‐dose nitrogen implantation induces an ion and damage profile in TiO₂ nanotubes that leads to “co‐catalytic” activity for photocatalytic H₂‐evolution (without the use of any noble metal). Ion implantation with adequate parameters creates this active zone limited to the top part of the tubes. The coupling of this top layer and the underlying non‐implanted part of the nanotubes additionally contributes to an efficient carrier separation and thus to a significantly enhanced H₂ generation.     

Site‐Selected Doping of Upconversion Luminescent Er3+ into SrTiO3 for Visible‐Light‐Driven Photocatalytic H2 or O2 Evolution

A series of upconversion luminescent erbium‐doped SrTiO₃ (ABO₃‐type) photocatalysts with different initial molar ratios of Sr/Ti have been prepared by a facile polymerized complex method. Er³⁺ ions, which were gradually transferred from the A to the B site with increasing Sr/Ti, enabled the absorption of visible light and the generation of high‐energy excited states populated by upconversion processes. The local internal fields arising from the dipole moments of the distorted BO₆ octahedra promoted energy transfer from the high‐energy excited states of Er³⁺ with B‐site occupancy to the host SrTiO₃ and thus enhanced the band‐to‐band transition of the host SrTiO₃. Consequently, the erbium‐doped SrTiO₃ species with B‐site occupancy showed higher photocatalytic activity than those with A‐site occupancy for visible‐light‐driven H₂ or O₂ evolution in the presence of the corresponding sacrificial reagents. The results generally suggest that the introduction of upconversion luminescent agents into host semiconductors is a promising approach to simultaneously harnessing low‐energy photons and maintaining redox ability for photocatalytic H₂ and O₂ evolution and that the site occupancy of doped elements in ABO₃‐type perovskite oxides greatly determines the photocatalytic activity.     

Preparation of Photocatalytic Au–Ag2Te Nanomaterials

A facile approach has been developed for the preparation of various morphologies of Au–Ag₂Te nanomaterials (NMs) that exhibit strong photocatalytic activity. Te NMs (nanowires, nanopencils, and nanorice) were prepared from TeO₂ in the presence of various concentrations (16, 8, and 4 M ) of a reducing agent (N₂H₄) at different temperatures (25 and 60 °C). These three Te NMs were then used to prepare Au–Ag₂Te NMs by spontaneous redox reactions with Au³⁺ and Ag⁺ ions sequentially. The Au–Ag₂Te nanopencils exhibit the highest activity toward degradation of methylene blue and formation of active hydroxyl radicals on solar irradiation, mainly because they absorb light in the visible region most strongly. All three differently shaped Au–Ag₂Te NMs (10 μg mL^?1) provide a death rate of Escherichia coli greater than 80 % within 60 min, which is higher than that of 51 % for commercial TiO₂ nanoparticles (100 μg mL^?1). Under light irradiation, the Au NPs in Au–Ag₂Te NMs enhance the overall photo‐oxidation ability of Ag₂Te NMs through faster charge separation because of good contact between Ag₂Te and Au segments. With high antibacterial activity and low toxicity toward normal cells, the Au–Ag₂Te NMs hold great potential for use as efficient antibacterial agents.     

离子交换法制备AgBr/Ag2WO4复合催化剂及其可见光催化性能

以Ag₂WO₄为载体,采用离子交换法合成了新型的AgBr/Ag₂WO₄复合光催化剂.利用XRD、SEM和UV-Vis对AgBr/Ag₂WO₄催化剂进行了表征,在可见光条件下(500 W、λ>420 nm)、以甲基橙(MO)为染料模型研究了AgBr/Ag₂WO₄的光催化活性.结果表明,AgBr/Ag₂WO₄具有比单独的AgBr和Ag₂WO₄更佳的催化活性,其中30%-AgBr/Ag₂WO₄复合催化剂具有最大光催化活性.机理研究表明,在MO的降解过程中,·O₂^-起主要作用,h⁺次之而·OH可以忽略.AgBr和Ag₂WO₄之间构成的异质结有效分离了光生电子和空穴,提高了催化剂的活性.     

A Facile Molecular Precursor‐based Synthesis of Ag2Se Nanoparticles and Its Composites with TiO2 for Enhanced Photocatalytic Activity

The reactions of different silver(I) reagents AgX (X^?=iodide, trifluoroacetate, triflate) with selenoethers R₂Se (R=Me, tBu) in a variety of solvents were investigated in relation with their use as precursors for Ag₂Se nanomaterials. Different reaction conditions led to different reactivities and afforded either molecular complexes or metal selenide nanoparticles. The reactions leading to in situ formation of the metal selenide nanoparticles were then extended in the presence of commercial TiO₂ (P25) to prepare silver selenide–titania nanocomposites with different Ag/Ti ratios. These nanocomposites, well characterized by elemental analysis (Ag, Se), PXRD, TEM, BET, XPS and UV/Vis studies, were investigated as photocatalysts for the degradation of formic acid (FA) solution. The xAg₂Se‐TiO₂ nanocomposites (x=0.01, 0.13 and 0.25 mol %) exhibited a much higher catalytic activity as compared to P25, which is an established benchmark for the photocatalysis under UV light, and retained a good photocatalytic stability after recycling for several times.     

Photocatalytic Reduction of Ag2SO4 by Dawson-Derived Sandwich Complex

Photocatalytic reduction of Ag^I₂SO₄ from aqueous solutions is observed in the presence of Dawson-derived sandwich type polyoxometalates (POMs) [M₄(P₂W₁₅O₅₆)₂]¹⁶⁻, M = Co²⁺, Ni²⁺ and Zn²⁺ as photocatalyst and an organic substrate (propan-2-ol) as sacrificial electron donor. The direct photochemical excitation of the Dawson-derived sandwich type polyoxometalates in the presence of propan-2-ol leads to its reduction. That first reduction step induces electron transfer to Ag⁺ ions to give Ag⁰ metal atoms which then form by aggregation colloidal metal nanoparticles stabilized by POM. In the case of [Co₄(P₂W₁₅O₅₆)₂]¹⁶⁻, TEM experiments reveal that the Ag_n particles obtained with a slight excess of Ag⁺ are almost spherical with size in the range 20 – 50 nm. However, in a large excess of Ag⁺, the obtained colloids are more oblate and assembled together to give larger aggregates.     

A Simple Method for the Preparation of TiO2/Ag‐AgCl@Polypyrrole Composite and Its Enhanced Visible‐Light Photocatalytic Activity

A novel and facile method was developed to prepare a visible‐light driven TiO₂/Ag‐AgCl@polypyrrole (PPy) photocatalyst with Ag‐AgCl nanoparticles supported on TiO₂ nanofibers and covered by a thin PPy shell. During the synthesis, the PPy shell and Ag‐AgCl nanoparticles were prepared simultaneously onto TiO₂ nanofibers, which simplified the preparation procedure. In addition, because Ag‐AgCl aggregates were fabricated via partly etching the Ag nanoparticles, their size was well controlled at the nanoscale, which was beneficial for improvement of the contact surface area. Compared with reference photocatalysts, the TiO₂/Ag‐AgCl@PPy composite exhibited an enhanced photodegradation activity towards rhodamine B under visible‐light irradiation. The superior photocatalytic property originated from synergistic effects between TiO₂ nanofibers, Ag‐AgCl nanoparticles and the PPy shell. Furthermore, the TiO₂/Ag‐AgCl@PPy composite could be easily separated and recycled without obvious reduction in activity.     

稀土离子掺杂对纳米TiO2光催化制氢活性的影响

采用溶胶-凝胶技术制备了纳米TiO2和一系列稀土离子掺杂的TiO2光催化剂,通过X射线衍射、透射电镜及N2吸附等技术对其进行了表征,考察了样品光催化分解水制氢的性能.结果表明,稀土离子掺杂有效抑制了TiO2粒子的生长,提高了粒子的分散性,增大了催化剂的比表面积,从而大幅度提高了其光催化分解水制氢的性能.其中,Gd3 掺杂的TiO2样品粒径最小,分散性最好,比表面积最大(是未掺杂TiO2的35倍).掺杂离子的电子构型对样品的光催化制氢活性有较大影响,具有全空电子构型的La3 和半充满电子构型的Gd3 掺杂的样品具有较高的光催化制氢活性(分别是未掺杂TiO2的3.69倍和3.72倍).     

A Bifunctional Hybrid Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions: Nano-Co3O4-Deposited La0.5Sr0.5MnO3 via Infiltration

For rechargeable metal–air batteries, which are a promising energy storage device for renewable and sustainable energy technologies, the development of cost-effective electrocatalysts with effective bifunctional activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been a challenging task. To realize highly effective ORR and OER electrocatalysts, we present a hybrid catalyst, Co₃O₄-infiltrated La_0.5Sr_0.5MnO_3-δ (LSM@Co₃O₄), synthesized using an electrospray and infiltration technique. This study expands the scope of the infiltration technique by depositing ~18 nm nanoparticles on unprecedented ~70 nm nano-scaffolds. The hybrid LSM@Co₃O₄ catalyst exhibits high catalytic activities for both ORR and OER (~7 times, ~1.5 times, and ~1.6 times higher than LSM, Co₃O₄, and IrO₂, respectively) in terms of onset potential and limiting current density. Moreover, with the LSM@Co₃O₄, the number of electrons transferred reaches four, indicating that the catalyst is effective in the reduction reaction of O₂ via a direct four-electron pathway. The study demonstrates that hybrid catalysts are a promising approach for oxygen electrocatalysts for renewable and sustainable energy devices.     

Ag2O/TiO2纳米线异质结的制备及可见光催化性能

采用化学沉积法制得了氧化银/二氧化钛纳米线异质结(Ag₂O/TNWs)可见光催化剂. 应用扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线衍射(XRD)和X射线光电子能谱(XPS)等手段对催化剂进行表征, 并以甲基橙降解为模型反应研究了其光催化性能. 结果表明, 与负载等量氧化银的二氧化钛纳米粒子(Ag₂O/P25)催化剂相比, Ag₂O/TNWs纳米线异质结具有优异的一维增强可见光催化性能.     

银沉积纳米TiO2光催化剂的制备及活性

银沉积纳米TiO2光催化剂的制备及活性;纳米TiO2; 银沉积; 光催化; 甲基橙     

镧在TiO2薄膜中的非均匀掺杂对光催化性能的影响

采用溶胶-凝胶法制备了La^3＋非均匀掺杂的TiO2薄膜。通过对甲基橙的光催化降解实验来评价催化剂薄膜的催化活性，结果表明：La^3＋的掺杂方式对TiO2的催化活性有很大的影响，采用非均匀掺杂方式可以明显提高TiO2的催化活性，掺杂浓度以0．5％（原子分数）为最佳。紫外-可见漫反射光谱鼎示其吸收带边明显红移；电化学行为表明其光生空穴一电子对的形成能力和分离效率得到提高。通过比较太阳能光电池异质结的“窗口效应”理论，初步探讨了La^3＋非均匀掺杂对TiO2的光催化活性的影响机制。     

Fe2O3–TiO2 Nanocomposites for Enhanced Charge Separation and Photocatalytic Activity

Photocatalysis provides a cost effective method for both renewable energy synthesis and environmental purification. Photocatalytic activity is dominated by the material design strategy and synthesis methods. Here, for the first time, we report very mild and effective photo‐deposition procedures for the synthesis of novel Fe₂O₃–TiO₂ nanocomposites. Their photocatalytic activities have been found to be dramatically enhanced for both contaminant decomposition and photoelectrochemical water splitting. When used to decompose a model contaminant herbicide, 2,4‐dichlorophenoxyacetic acid (2,4‐D), monitored by both UV/Vis and total organic carbon (TOC) analysis, 10 % Fe–TiO₂–H₂O displayed a remarkable enhancement of more than 200 % in the kinetics of complete mineralisation in comparison to the commercial material P25 TiO₂ photocatalyst. Furthermore, the photocurrent is nearly double that of P25. The mechanism for this improvement in activity was determined using density functional theory (DFT) and photoluminescence. These approaches ultimately reveal that the photoelectron transfer is from TiO₂ to Fe₂O₃. This favours O₂ reduction which is the rate‐determining step in photocatalytic environmental purification. This in situ charge separation also allows for facile migration of holes from the valence band of TiO₂ to the surface for the expected oxidation reactions, leading to higher photocurrent and better photocatalytic activity.     

Active Electron Density Modulation of Co3O4‐Based Catalysts Enhances their Oxygen Evolution Performance

Despite the fact that many strategies have been developed to improve the efficiency of the oxygen evolution reaction (OER), the precise modulation of the surface electronic properties of catalysts to improve their catalytic activity is still challenging. Herein, we demonstrate that the surface active electron density of Co₃O₄ can be effectively regulated by an argon‐ion irradiation method. X‐ray photoelectron and synchrotron x‐ray absorption spectroscopy, UV photoelectron spectrometry, and DFT calculations show that the surface active electron density band center of Co₃O₄ has been upshifted, leading to a significantly enhanced absorption capability of the oxo group. The optimized Co₃O₄‐based catalysts exhibit an excellent overpotential of 260 mV at 10 mA cm^?2 and Tafel slope of 54 mV dec^?1, superior to the capability of the benchmark RuO₂, representing one of the best Co‐based OER catalysts. This approach could guide the future rational design and discovery of ideal electrocatalysts.     

波长对Ag/TiO2催化剂上二氧化碳光催化还原的影响

Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction.     

Sonochemical Synthesis of Ag/AgCl Nanocubes and Their Efficient Visible‐Light‐Driven Photocatalytic Performance

A novel one‐step sonochemical approach to synthesize a plasmonic photocatalyst of AgCl nanocubes (ca. 115 nm in edge length) with a small amount of Ag metal species is presented. The nanoscale Ag/AgCl hybrid photocatalysts with cubic morphology are readily formed under ambient ultrasonic conditions and neither external heat treatment nor reducing agents are required. The size of the Ag/AgCl photocatalysts could be controlled by changing the concentrations of Ag⁺ ions and polyvinylpyrrolidone molecules in precursor solutions. The compositions, microstructures, influencing factors, and possible growth mechanism of the Ag/AgCl hybrid nanocubes were systematically investigated. The Ag/AgCl photocatalysts show excellent photocatalytic performance for degradation of various dye molecules under visible light.     

La1-xSrxCoC3钙钛矿在碱性溶液中的析氧电催化

 稳态极化研究结果表明, La1-xSrxCoO3电极的析氧Tafel斜率为2303RT/F, OH-的反应级数近似为1, 在阳极析氧反应中, OH-的电化学脱附为速度控制步骤. 随着La1-xSrxCoO3中Sr含量的增加,氧化物表面的粗糙度提高,当x=02时,析氧反应的活化能最低,即La0.8Sr0.2CoO3表现有最高的析氧电催化活性.     

Ion‐Exchange‐Induced 2D–3D Conversion of HMA1−xFAxPbI3Cl Perovskite into a High‐Quality MA1−xFAxPbI3 Perovskite

High‐quality phase‐pure MA_1?xFA_xPbI₃ planar films (MA=methylammonium, FA=formamidinium) with extended absorption and enhanced thermal stability are difficult to deposit by regular simple solution chemistry approaches owing to crystallization competition between the easy‐to‐crystallize but unwanted δ‐FAPbI₃/MAPbI₃ and FA_xMA_1?xPbI₃ requiring rigid crystallization conditions. Here A 2D–3D conversion to transform compact 2D mixed composition HMA_1?xFA_xPbI₃Cl perovskite precursor films into 3D MA_1?xFA_xPbI₃ (x=0.1–0.9) perovskites is presented. The designed Cl/I and H/FA(MA) ion exchange reaction induced fast transformation of compact 2D perovskite film, helping to form the phase‐pure and high quality MA_1?xFA_xPbI₃ without δ‐FAPbI₃ and MAPbI₃ impurity. In all, we successfully developed a facile one‐step method to fabricate high quality phase‐pure MA_1?xFA_xPbI₃ (x=0.1–0.9) perovskite films by 2D–3D conversion of HMA_1?xFA_xPbI₃Cl perovskite. This 2D–3D conversion is a promising strategy for lead halide perovskite fabrication.