Z-scheme mechanism for methylene blue degradation over Fe2O3/g-C3N4 nanocomposite prepared via one-pot exfoliation and magnetization of g-C3N4

The low surface area, high recombination rate of photogenerated charge carriers, narrow visible range activity, and difficulty in the separation from cleaned solutions limit the wide application of g-C₃N₄ as a photocatalyst. Herein, we have succeeded in developing a one-pot strategy to overcome the above-mentioned difficulties of g-C₃N₄. The broadening of the visible-light response range and inducing magnetic nature to g-C₃N₄ was succeeded by preparing a nanocomposite with Fe₂O₃ via a facile solvothermal method. The preparation method additionally imparted layer exfoliation of g-C₃N₄ as evident from the XRD patterns and TEM images. The strong interaction between the components is revealed from the XPS analysis. The broadened visible-light absorbance of Fe₂O₃/g-C₃N₄ with a Z-scheme photocatalytic degradation mechanism is well evident from the UV‒Vis DRS analysis and PL measurement of the composite with terephthalic acid. The active species of photocatalysis were further investigated using scavenging studies in methylene blue degradation that revealed hydroxyl radicals and holes as the major contributors to the activity of Fe₂O₃/g-C₃N₄.     

Microwave hydrothermal synthesis of WO3(H2O)0.333/CdS nanocomposites for efficient visible-light photocatalytic hydrogen evolution

WO₃(H₂O)_0.333/CdS (WS) nanocomposites are obtained via a rapid microwave hydrothermal method, and they are served as visible light-driven photocatalysts for the H₂ generation. By using Pt as the cocatalyst, the WS nanocomposite with 70 wt.% CdS reaches the H₂ evolution rate of 10.32 mmol·g⁻¹·h⁻¹, much quicker than those of WO₃(H₂O)_0.333 and CdS. The cycling test reveals the good photocatalytic stability of the WS nanocomposite. The carrier transfer mechanism of WS nanocomposites can be explained by the Z-scheme mechanism. The existence of the Z-scheme heterojunction greatly helps to separate photogenerated carriers and thus improves the photocatalytic activity. The present work provides a rapid synthesis method for preparing Z-scheme heterojunction photocatalysts, and may be helpful for the green production of hydrogen.     

Z-机制光催化剂Cd1-xZnxS@WO3-x和Cd1-xZnxS@WO3-x/CoOx/NiOx及其高效可见光解水产氢活性研究（英文）

人工Z-机制光催化剂因其同时具有光吸收范围宽、电荷分离效率高以及载流子氧化还原能力强等优势受到了研究者们的广泛关注.然而,设计和制备能够利用太阳能进行高效光解水产氢的低成本、高稳定性非贵金属Z-机制光催化剂仍具有挑战性.本文报道了一种新颖的全固态Z-机制光催化剂Cd1-xZnxS@WO3-x,该催化剂纳米结构是由氧缺陷WO3-x非晶层包覆Cd1-xZnxS纳米棒组成.研究结果表明,由于适量的Zn掺杂使得Cd1-xZnxS具有更强的产生还原性电子能力,同时, WO3-x超薄非晶层中引入的氧空位(W^5+/OVs)有效地促进了电荷的分离,使得该Z-机制Cd1-xZnxS@WO3-x光催化材料具有优异的光催化产氢反应(HER)活性,且显著高于贵金属Pt负载的Cd1-xZnxS纳米棒(Pt/Cd1-xZnxS及绝大多数WO3和CdS基光催化剂.优化后的Cd1-xZnxS@WO3-x复合光催化剂的HER速率可达21.68 mmol h^-1g^-1.进一步通过原位光沉积负载CoOx和NiO--x双共催化剂, Cd1-xZnxS@WO3-x/Co Ox/Ni Ox复合材料的活性高达28.25 mmol h^-1g^-1,约为Pt/Cd1-xZnxS的12倍.计算结果表明, Cd1-xZnxS@WO3-x在420 nm激发光下的HER表观量子产率(AQY)为34.6%,而负载CoOx和Ni Ox双共催化剂后的Cd1-xZnxS@WO3-x/Co Ox/Ni Ox的AQY提高到了60.8%.此外, Cd1-xZnxS@WO3-x和Cd1-xZnxS@WO3-x/CoOx/NiOx均表现出了良好的长时间HER稳定性.该工作将为理性设计和制备高效光解水产氢催化剂提供新视角.     

WO3-Ag/石墨相C3N4 Z型复合光催化剂的合成及其光催化性能

采用水热法合成WO₃纳米棒，并通过简单的溶剂蒸发法及光沉积法实现WO₃-Ag/石墨相C₃N₄(g-C₃N₄)复合光催化剂的合成。采用XRD、SEM、TEM等对材料进行全面表征。结果表明，由于成功构建了Z型异质结，WO₃-Ag/g-C₃N₄复合光催化剂能够拓展可见光响应，有效抑制光生电子与空穴复合。最佳工艺条件下所得WO₃-Ag/g-C₃N₄复合光催化剂在100 min时光催化降解罗丹明B (RhB)的效率可达96.8%，且WO₃-Ag/g-C₃N₄复合光催化剂具有优异的稳定性。光催化机制表明，光催化实验中真正的活性物质为羟基自由基与超氧自由基。      

Er3+/Yb3+掺杂NaGd(WO4)2粉体的制备与发光性能

采用水热法成功制备了Er~(3+)/Yb~(3+)双掺杂的NaGd(WO_4)_2纳米粉体,研究了不同络合剂、水热温度对样品形貌和结构的影响。测量了不同Er~(3+)掺杂浓度样品的可见上转换和近红外发射光谱。结果表明:在980nm LD激发下,可观测到样品强烈的绿色上转换发光,对应Er~(3+)的~2H_(11/2)→~4I_(15/2)(530nm)和~4S_(3/2)→~4I_(15/2)(552nm)跃迁,以及较弱的红色上转换和近红外发光,分别对应Er~(3+)的~4F_(9/2)→4I15/2(656nm)和~4I_(13/2)→~4I_(15/2)(1 532nm)跃迁。且随着Er~(3+)掺杂浓度的增加,样品的上转换红绿光和1.54μm附近的近红外光均呈现出先增大后减小的趋势。样品的激发和发射光谱显示,在378nm处的激发峰最强,对应Er~(3+)的~4I_(15/2)→~4 G_(11/2)能级跃迁,最强发射峰位于552nm。根据泵浦功率与发光强度的关系可以得出,红光和绿光的发射主要为双光子吸收过程,但红光还包含了一定的单光子吸收成分。     

超临界流体干燥法制备TiO2/ Fe2O3 和TiO2/ Fe2O3/ SiO2 复合纳米粒子及光催化性能

以TiCl₄ 、Fe (NO₃ )₃·9H₂O 和Na₂SiO₃19H₂O 为原料, 采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO₂/ Fe₂O₃ 和TiO₂/ Fe₂O₃/ SiO₂ 复合光催化剂。以光催化降解苯酚对所得催化剂的催化活性进行了评价。结果表明, 纳米TiO₂/ Fe₂O₃ 复合粒子与单组分TiO₂ 比较, 复合粒子光催化活性高于单组分的TiO₂, 6h 苯酚降解率高达95.9 %。SiO₂ 的加入可以抑制纳米粒子粒径的长大和晶相的转变, 增强TiO₂ 纳米粒子的热稳定性。复合光催化剂中Fe₂O₃ 最佳掺入量为0.06 %, SiO₂ 最佳掺入量为10 %(摩尔分数) 。并用XRD、TEM 和FTIR 等手段进行了表征。TiO₂ 以锐钛矿型形式存在, SiO₂ 以无定性形式存在。比较了不同制备方法制得的TiO₂/ Fe₂O₃ 复合光催化剂, 得出超临界干燥法制备的光催化剂具有粒径小、比表面积大、分散性好、光催化活性高等特点。采用超临界流体干燥可直接得锐钛型纳米复合光催化剂。     

A true nanocomposite: Single crystalline Au nanoparticles on single crystalline Fe3O4 nanoparticles

An Au/Fe₃O₄ nanocomposite catalyst was fabricated through a simple deposition-precipitation method. The Au/Fe₃O₄ nanocomposite is a true nanocomposite that has single crystalline Au nanoparticles supported on single crystalline Fe₃O₄ nanoparticles. Lattice fringes from both Au and Fe₃O₄ single nanoparticles were simultaneously observed by transmission electron microscope (TEM). This nanocomposite catalyst showed much high activity in low temperature CO oxidation reaction. The Au/Fe₃O₄ nanocomposite catalyst reaches 100% CO conversion at 40 °C. In comparison, Au/commercial Fe₃O₄ catalyst needs 375 °C to convert CO. This Au/Fe₃O₄ nanocomposite is an ideal sample to study synergetic effect between the catalyst and the support at nanoscale.     

Co3O4负载rGO/g-C3N4臭氧光催化降解2,4-二氯苯氧乙酸活性研究

通过简单的水热法制备了Co₃O₄/rGO/g-C₃N₄催化剂,并在可见光照射下用于光催化臭氧氧化降解2,4-二氯苯氧乙酸(2,4-D)。利用XRD, SEM, TEM, XPS, UV-vis DRS, FT-IR和瞬态光电流对样品进行测试表征。研究表明,Co₃O₄, rGO和g-C₃N₄形成异质结后光生电子-空穴(e^--h⁺)对的分离效率,e^-的迁移能力以及光催化臭氧氧化活性都明显提升。此外,0.5Co₃O₄/0.25rGO/GCN对2,4-D具有100%的去除率,并具有最高反应速率(k=0.070 9 min^-1)。经过计算得出光催化臭氧氧化2,4-D的协同因子为3.91,表明光催化和臭氧氧化间具有较好的协同效应。活性组分的捕获实验结果表明h⁺和·OH是光催...     

Novel synthesis of Cu-HAP/SiO2@carbon nanocomposites as heterogeneous catalysts for Fenton-like oxidation of 2,4-DCP

Hydroxyapatite (HAP) has stable ion exchange capacity and is a potential environmental catalyst carrier. In this paper, a novel metal–carbon nanocomposite (Cu-HAP/SiO₂@carbon) was synthesized as a catalyst to remove 2,4-DCP. The SEM, XRD, FT-IR, XPS and BET were used to characterize the synthesized catalyst materials, the results showed that Cu-HAP/SiO₂@carbon has a rich pore structure and a high specific surface area, and the copper element is well dispersed on the surface of the carrier. The results of 2,4-DCP removal effect showed that almost 100 % of 2,4-DCP was removed under the optimal reaction conditions. In addition, the Cu-HAP/SiO₂@carbon broaden the applicable pH range and has excellent performance in terms of reusability (93.73 % of removal rate after 5 cycles). Finally, based on the intermediate products identify by HPLC, the degradation mechanism and possible degradation pathway of 2,4-DCP was investigated, EPR was employed to confirm the effects of ·OH.     

SrTiO3-CaCr0.5Nb0.5O3 solid solutions as p-type photocatalysts for Z-scheme water splitting under visible light illumination

P-type semiconductivity has been observed in solid solution series (SrTiO3)1-x(CaCr0.5Nb0.5O3)x (0.0 ≤x ≤ 0.15),which all adopt cubic symmetry and own intense absorption in the visible light region.These solid solutions are superior H2 evolution photocatalysts under visible light illumination (λ ≥400 nm).An AQE as high as 1.02 ％ at 420 ± 20 nm has been achieved at optimal composition(SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15 which significantly surpasses the parent compounds.Stoichiometric H2/O2 production under visible light illumination has been successfully realized using Z-scheme system containing (SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15,WO3 and I-/IO3-redox couple.     

La/TiO2-SiO2薄膜的光催化性能研究

采用溶胶-凝胶法制备了不同掺杂量的La／TiO2-SiO2复合薄膜．通过XRD、FE-SEM和AFM研究了复合薄膜的微观结构，采用紫外光照射下亚甲基蓝的分解实验比较薄膜的光催化性能．结果表明：La掺杂可显著提高TiO2-SiO2复合薄膜的光催化活性，以5％掺杂量为最佳，其光降解率比掺杂前提高了约23％．薄膜活性提高的主要原因是La掺杂后细化了TiO2的晶粒，提高了薄膜的比表面积，使其具有更高的氧化还原电势，La^3＋取代Ti^4＋进入到TiO2晶格，引起晶格膨胀，这种不同价离子的取代导致TiO2粒子表面电荷分布不平衡，从而提高了光生电子-空穴的分离效率．     

Cross‐Linked g‐C3N4/rGO Nanocomposites with Tunable Band Structure and Enhanced Visible Light Photocatalytic Activity

Cross‐linked rather than non‐covalently bonded graphitic carbon nitride (g‐C₃N₄)/reduced graphene oxide (rGO) nanocomposites with tunable band structures have been successfully fabricated by thermal treatment of a mixture of cyanamide and graphene oxide with different weight ratios. The experimental results indicate that compared to pure g‐C₃N₄, the fabricated CN/rGO nanocomposites show narrowed bandgaps with an increased in the rGO ratio. Furthermore, the band structure of the CN/rGO nanocomposites can be readily tuned by simply controlling the weight ratio of the rGO. It is found that an appropriate rGO ratio in nanocomposite leads to a noticeable positively shifted valence band edge potential, meaning an increased oxidation power. The tunable band structure of the CN/rGO nanocomposites can be ascribed to the formation of C?O?C covalent bonding between the rGO and g‐C₃N₄ layers, which is experimentally confirmed by Fourier transform infrared (FT‐IR) and X‐ray photoelectron (XPS) data. The resulting nanocomposites are evaluated as photocatalysts by photocatalytic degradation of rhodamine B (RhB) and 4‐nitrophenol under visible light irradiation (λ > 400 nm). The results demonstrate that the photocatalytic activities of the CN/rGO nanocomposites are strongly influenced by rGO ratio. With a rGO ratio of 2.5%, the CN/rGO‐2.5% nanocomposite exhibits the highest photocatalytic efficiency, which is almost 3.0 and 2.7 times that of pure g‐C₃N₄ toward photocatalytic degradation of RhB and 4‐nitrophenol, respectively. This improved photocatalytic activity could be attributed to the improved visible light utilization, oxidation power, and electron transport property, due to the significantly narrowed bandgap, positively shifted valence band‐edge potential, and enhanced electronic conductivity.     

石墨烯桥联的ZnO/Ag3PO4复合材料的制备及其对环丙沙星的降解性能

采用沉淀沉积法制备了石墨烯桥联的ZnO/Ag₃PO₄复合光催化材料,具有优异的可见光催化性能,通过XRD、XPS、SEM、EDS、BET、FTIR、UV-Vis DRS、PL及ESR等表征手段对其晶体结构、形貌、光学性质等进行了表征及分析,并研究了不同氧化石墨烯比例的GO-ZnO/Ag₃PO₄复合材料对模拟抗生素废水环丙沙星(CIP)的光催化降解性能。由于GO及ZnO的引入,不仅增强了GO-ZnO/Ag₃PO₄对可见光吸收,且拥有了更高的电子-空穴对的分离效率。当GO与Ag₃PO₄的质量比为1%时,GO-ZnO/Ag₃PO₄显示出最佳的光催化活性,60 min可见光照后对CIP降解率可达85.3%。捕获实验表明,超氧自由基(·O₂?)是反应过程中的主要活性物质,ZnO与Ag₃PO₄之间形成了异质结,符合Z型电子转移机制,GO的引入进一步提高了电子的快速转移,并使Z型体系更加稳定。经过6次光催化循环,降解率依然保持在70%以上,表明GO-ZnO/Ag₃PO₄复合材料具有优异的稳定性。      

WS2/g-C3N4异质结光催化分解水制氢性能及机制

通过溶剂蒸发和二次高温煅烧石墨相碳化氮(g-C₃N₄)纳米片和WS₂纳米片混合物构建WS₂/g-C₃N₄异质结,该异质结保留g-C₃N₄和WS₂主体结构的同时,在界面处形成化学键,确保该异质结的化学稳定性和热稳定性。光催化分解水制氢实验表明,WS₂纳米片含量为3wt%时光催化制氢速率高达68.62 μmol/h,分别是g-C₃N₄纳米片和WS₂纳米片的2.53倍和15.29倍,表明异质结的构建可大幅提升g-C₃N₄的光催化性能,循环实验表明该异质结在5次循环实验后光催化性能没有明显下降,表明该异质结的稳定性较好。光电性能测试表明异质结的构建不仅提高激发电子的转移效率,同时抑制激发电子空穴的复合率,大幅提升激发电子的利用效率,致使光催化分解水制氢速率较g-C₃N₄纳米片和WS₂纳米片大幅提升。      

Visible light active ZnIn2S4/g-C3N4 heterostructure nanocomposite photoelectrode for efficient photoelectrochemical water splitting activity

Hexagonal zinc indium sulfide coupled g-C₃N₄ (H-ZnIn₂S₄/g-C₃N₄) nanocomposites were synthesized using chemisorption method and its performance towards photoelectrochemical water splitting activity was studied. The H-ZnIn₂S₄/g-C₃N₄ (H-ZIS/CN) nanocomposites exhibited ∼ 1.9 times enhanced photoelectrochemical performance as compared to the H-ZnIn₂S₄. The enhancement in the PEC water splitting activity of H-ZIS/CN nanocomposite is ascribed to the formation of type-II heterojunction which resulted in improved separation of photogenerated charge carriers and faster transfer of charges at the photoelectrode/electrolyte interface. The electrochemical impedance study and Mott-Schottky supported these results. Moreover, during photoelectrochemical reactions, H-ZIS/CN nanocomposites showed tremendous stability under visible light. A potential mechanism of the enhanced photoelectrochemical activity of H-ZIS/CN nanocomposites was proposed and endorsed by the PEC results. This study demonstrates that establishing a heterostructure system by coupling a ternary chalcogenide semiconductor with a conducting polymer is an effective strategy for PEC water splitting applications.     

Ag-Ag2O/TiO2-g-C3N4纳米复合材料的制备及可见光催化性能

近年来,半导体光催化技术作为一项快速发展的新型环保技术,在降解水体中污染物和可再生清洁能源的生产领域有很大的应用前景。本文以所制备出的20 wt%类石墨烯碳氮化合物(g-C₃N₄)/TiO₂为基质,利用水热法中纳米Ag颗粒部分氧化行为成功合成了Ag修饰异质结型Ag-Ag₂O/TiO₂-g-C₃N₄复合材料。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-Vis DRS)、光致荧光光谱(PL)、瞬态光电流响应等分析测试手段对Ag-Ag₂O/TiO₂-g-C₃N₄复合材料的晶体结构、形貌、光学性质等进行表征和分析。以亚甲基蓝溶液为目标降解物,研究了Ag-Ag₂O/TiO₂-g-C₃N₄复合材料的可见光催化性能。结果表明:在纳米Ag颗粒修饰的Ag-Ag₂O/TiO₂-g-C₃N₄复合材料中,Ag部分氧化成Ag₂O;与g-C₃N₄的协同作用使Ag-Ag₂O/TiO₂-g-C₃N₄复合催化剂具有良好的可见光催化活性;可见光照射4 h后,Ag-Ag₂O/TiO₂-g-C₃N₄复合催化剂对亚甲基蓝的降解率接近50%。      

微乳液水热法制备钨酸铋光催化剂及性能研究

采用微乳液介导水热法制备Bi2WO6和Fe/Bi2WO6光催化剂,并研究水热反应温度、前驱体pH值、水相与表面活性剂的摩尔比ω值和Fe3+掺杂量对光催化剂结构、形貌和光催化活性等方面的影响.结果表明:合成的Bi2WO6为15～25 nm的纳米球状结构;当前驱体pH=1、水热温度为150℃下合成的Bi2WO6催化剂对亚甲基蓝(MB)的降解率达到93.8%;当ω=27时合成的Bi2WO6对MB光催化降解率达到了97.8%.研究发现当掺入1.03%的Fe3+的Bi2WO6比纯Bi2WO6对MB的降解率提高了2倍,达到90.2%.     

Phase-junction Ag/TiO2 nanocomposite as photocathode for H2 generation

Developing anatase/rutile phase-junction in TiO2 to construct Z-scheme system is quite effective to improve its photoelectrochemical activity.In this work,the anatase/rutile phase-junction Ag/TiO2 nanocomposites are developed as photocathodes for hydrogen production.The optimized Ag/TiO2 nanocomposite achieves a high current density of 1.28 mA cm-2,an incident photon-to-current con-version efficiency(IPCE)of 10.8％,an applied bias photon-to-current efficiency(ABPE)of 0.32 at 390 nm and a charge carriers'lifetime up to 2000s.Such enhancement on photoelectrochemical activity can be attributed to:(i)the generated Z-scheme system in the anatase/rutile phase-junction Ag/TiO2 photocath-ode enhances the separation,diffusion and transformation of electron/hole pairs inside the structure,(ii)Ag nanodots modification in the anatase/rutile phases leading to the tuned band gap with enhanced light absorption and(iii)the formed Schottky barrier after Ag nanodots surface modification provides enough electron traps to avoid the recombination of photogenerated electrons and holes.Our results here sug-gest that developing phase-junction nanocomposite as photocathode will provide a new vision for their enhanced photoelectrochemical generation of hydrogen.     

基于Pd/Fe3O4/rGO纳米复合材料的H2O2无酶传感器

环境监测、食品工业、临床、制药等领域对过氧化氢(H_2O_2)的快速、准确检测有极大的需求,而电化学检测方法由于灵敏度高、响应快、检测限低等特点被认为是最理想的H_2O_2检测方法.本文利用电化学沉积的方法将Pd纳米颗粒沉积到四氧化三铁/石墨烯(Fe_3O_4/rGO)纳米复合材料修饰的玻碳电极表面,形成基于新型磁性纳米复合材料的H_2O_2无酶传感器;并采用循环伏安和计时安培电流等方法对修饰电极的电化学性能进行了表征.结果表明:制备的Pd/Fe_3O_4/r GO/GCE对H_2O_2的催化还原显示出较好的电催化活性,Pd纳米颗粒和Fe_3O_4/rGO在催化H_2O_2还原的过程中表现出了良好的协同作用.测定H_2O_2的线性范围为0.05~1 m M和1~2.6 m M两段,最低检测限达到3.918μM(S/N=3).并且该传感器具有较高的灵敏度和较好的重现性和抗干扰性,具有一定的实际应用价值.     

新型SnO2/WO3双层薄膜NO2敏感性能研究

采用射频磁控反应溅射锡(Sn)靶和钨(W)靶的方法制备了SnO2/WO3双层薄膜材料,通过XRD和XPS实验研究了双层薄膜的物相结构和组份,结果表明,SnO2/WO3双层薄膜经过热处理后形成了SnWO4化合物.在此基础之上,制作了相应的NO2气体敏感薄膜传感器,研究了双层薄膜传感器的制备工艺参数及工作条件对传感器性能的影响,研究了传感器的敏感特性,包括灵敏度、选择性、响应恢复等特性.结果表明,传感器对NO2气体有较好的敏感性,对其他干扰气体不敏感.