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1.
Nitrogen self-doped TiO(2) nanosheets with exposed {001} facets (ca. 67%) were synthesized by solvothermal treatment of TiN in a HNO(3)-HF ethanol solution and exhibited much higher visible-light photocatalytic H(2)-production activity than nitrogen doped TiO(2) microcrystallites with exposed {001} facets (ca. 60%) by a factor of 4.1.  相似文献   

2.
The production of clean and renewable hydrogen through water splitting using photocatalysts has received much attention due to the increasing global energy crises. In this study, a high efficiency of the photocatalytic H(2) production was achieved using graphene nanosheets decorated with CdS clusters as visible-light-driven photocatalysts. The materials were prepared by a solvothermal method in which graphene oxide (GO) served as the support and cadmium acetate (Cd(Ac)(2)) as the CdS precursor. These nanosized composites reach a high H(2)-production rate of 1.12 mmol h(-1) (about 4.87 times higher than that of pure CdS nanoparticles) at graphene content of 1.0 wt % and Pt 0.5 wt % under visible-light irradiation and an apparent quantum efficiency (QE) of 22.5% at wavelength of 420 nm. This high photocatalytic H(2)-production activity is attributed predominantly to the presence of graphene, which serves as an electron collector and transporter to efficiently lengthen the lifetime of the photogenerated charge carriers from CdS nanoparticles. This work highlights the potential application of graphene-based materials in the field of energy conversion.  相似文献   

3.
等离激元效应在光催化体系中的集成为实现广谱光吸收提供了一个新的途径,然而等离激元热电子的较低迁移率和不确定扩散方向使得其光催化效率仍较低.等离激元金属与n型半导体接触后,其界面间会形成肖特基结.在特定波长太阳光照射下,等离激元金属将其表面等离子体能量聚集在表面自由电子上,进而产生热电子.当这些热电子具有的能量高于肖特基势垒时,热电子便可注入到半导体导带上.与此同时,半导体上的电子可以通过肖特基接触发生回流,与金属上的空穴复合,进而降低半导体-等离激元金属复合材料的光催化性能.因此,为了提高光催化效率,如何调控等离激元热电子迁移和充分利用等离激元效应是一个重要挑战.本文尝试将"表面异质结"与肖特基结相结合的复合结构,得以有效地调控等离激元热电子的迁移.在该复合结构中,金纳米颗粒和铂纳米颗粒分别作为等离激元吸光单元和助催化剂,集成在TiO_2纳米片表面.其中"表面异质结"是由TiO_2纳米片的两种不同表面晶面所构成,我们选择由{001}和{101}两组晶面组成的TiO_2纳米片作为半导体衬底.该结构中的{001}晶面导带能级高于{101}导带能级,因而电子由高能级的{001}流向低能级的{101}晶面,可以用来引导等离激元热电子从可见光响应的金纳米颗粒向TiO_2进行高效转移.通过巯基丙酸的桥联作用,将等离激元Au纳米颗粒锚定在TiO_2纳米片的{001}晶面上,获得Au-TiO_2{001}样品.另一方面,利用TiO_2纳米片自身光生电荷导向性光沉积,得到与{101}晶面结合形成的Au-TiO_2{101}样品.我们对两组样品进行光电流和光催化产氢实验对比,确认在"表面异质结"诱导下Au-TiO_2{001}样品中Au产生的光生热电子可以更好地注入到TiO_2纳米片导带上.我们进一步通过光沉积Pt纳米颗粒来判定光生电子所能到达的区域,验证了以上结论.与此同时,肖特基结由铂纳米颗粒与TiO_2纳米片所形成,可以促使电子由TiO_2向铂纳米颗粒进行转移,而避免发生向金纳米颗粒的反向迁移,从而在Au-TiO_2体系中实现高效的单向载流子转移.基于该设计,等离激元光催化剂实现了明显改善的全谱光催化产氢性能.本文为全谱光催化的复合结构理性设计提供了一个新的思路.  相似文献   

4.
马松  徐兴民  谢君  李鑫 《催化学报》2017,(12):1970-1980
光催化产氢技术是目前解决能源和环境问题的最有潜力的方法之一,因此制备安全高效的光催化剂已成为目前的研究热点.在目前研究的各种光催化剂中,CdS光催化剂因为具有较窄的带隙(2.4 eV)和合适的导带位置,所以在可见光催化产氢领域受到广泛关注.然而,光生电子/空穴对易复合和光腐蚀作用极大地限制了CdS光催化剂的放大应用.因此,人们采用众多改性策略以提高CdS光催化剂的可见光产氢活性,其中构建CdS纳米结构和负载助催化剂被认为是最有效的方式.构建CdS纳米结构既可以缩短载流子的迁移路径,也可以减少CdS晶体中的缺陷.很多不同纳米结构的CdS光催化剂已经被开发,例如纳米线、纳米颗粒和纳米棒等.因为制备过程极为复杂繁琐,所以CdS纳米片的研究鲜见报道.本文采用乙酸鎘和硫脲为原材料,通过简单的溶剂热法合成了CdS纳米片.在CdS的各类助催化剂中,由于常用的Pt,Ag和Au等贵金属的高成本和低储量等问题严重限制了它们的实际应用,所以近年来众多非贵金属助催化剂(例如MoS_2,WS2,NiS,NiO和WC等)得到了广泛关注.由于非贵金属助催化剂存在弱电导率和低功函数等问题,影响了对光生电子的收集和利用.纳米碳材料具有极高的电导率、强可见光吸收、有效的载流子分离和较多的反应位点等优点,因此组合纳米碳材料和非贵金属助催化剂被认为是一种有效的解决方案.本文首次采用炭黑和NiS_2作为双助催化剂改性CdS纳米片,通过简单的溶剂热/沉淀两步法成功合成了廉价高效的CdS/CB/NiS_2三元光催化体系.光催化产氢性能测试表明,CdS-0.5%CB-1%NiS_2展现出最高的光催化效率(166.7μmol h~(-1)),分别是CdS NSs和CdS-1.0%NiS_2的5.16和1.87倍.X射线衍射、高分辨电子显微镜和X射线光电子能谱结果证实了CdS催化剂的片状结构,且炭黑和NiS_2成功负载在CdS纳米片表面.紫外-可见漫反射结果表明,随着炭黑和NiS_2的负载,复合催化剂的吸收边缘产生明显的红移,且对可见光的吸收增强.荧光光谱、阻抗和瞬态光电流曲线测试结果证明,炭黑和NiS_2的加入可以有效地促进光生电子/空穴对分离.极化曲线结果表明,加入炭黑和NiS_2可以降低CdS的产氢过电势,因此加速表面产氢动力学.总之,炭黑和NiS_2之间显著的协同效应极大地提高了可见光吸收,促进光生电子/空穴对分离,加速表面产氢动力学,最终得到了三元光催化体系极高的光催化产氢活性.  相似文献   

5.
Nitrogen and sulfur co-doped TiO(2) nanosheets with exposed {001} facets (N-S-TiO(2)) were prepared by a simple mixing-calcination method using the hydrothermally prepared TiO(2) nanosheets powder as a precursor and thiourea as a dopant. The resulting samples were characterized by transmission electron microscope, X-ray diffraction, N(2) adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and UV-Vis absorption spectroscopy. The electronic properties of N,S co-doped TiO(2) were studied using the first-principle density functional theory (DFT). The photocatalytic activity of N-S-TiO(2) was evaluated by degradation of 4-chlorophenol (4-CP) aqueous solution under visible light irradiation. The production of hydroxyl radicals (˙OH) on the surface of visible-light-irradiated samples was detected by photoluminescence technique using terephthalic acid as a probe molecule. The results show that nitrogen and sulfur atoms were successfully incorporated into the lattice of TiO(2), which resulted in N-S-TiO(2) samples exhibiting stronger absorption in the UV-visible range with a red shift in the band gap transition. The first-principle DFT calculations further confirm that N and S co-dopants can induce the formation of new energy levels in the band gap, which is associated with the response of N-S-TiO(2) nanosheets to visible light irradiation. Surprisingly, pure TiO(2) nanosheets show the visible-light photocatalytic activity for the degradation of 4-CP mainly due to the substrate-surface complexation of TiO(2) and 4-CP, which results in extending absorption of titania to visible light region through ligand-to-titanium charge transfer. The N-S-TiO(2) samples studied exhibited an enhanced visible-light photocatalytic activity than pure TiO(2). Especially, the doped TiO(2) sample at the nominal weight ratio of thiourea to TiO(2) powder of 2 showed the highest photocatalytic activity, which was about twice greater than that of Degussa P25. The enhanced activity of N-S-TiO(2) can be primarily attributed to the synergetic effects of two factors including the intense absorption in the visible-light region and the exposure of highly reactive {001} facets of TiO(2) nanosheets. The former is beneficial for the photogeneration of electrons and holes participating in the photocatalytic reactions, and the latter facilitates adsorption of 4-CP molecules on the surface of TiO(2) nanosheets.  相似文献   

6.
Zhou  Peng  Zhang  Hongna  Ji  Hongwei  Ma  Wanhong  Chen  Chuncheng  Zhao  Jincai 《中国科学:化学(英文版)》2020,63(3):354-360
Identifying the active catalytic centers on catalyst surface is significant for exploring the catalytic reaction mechanism and further guiding the synthesis of high-performance catalysts.However,it remains a challange in developing the site-specific technology for the identification of the active catalytic centers.Herein,in-situ infrared spectroscopy of adsorbed CO,photocatalytic hydrogen evolution reaction(HER) test and theoretical simulation were used to distinguish and quantify the different surface sites and their H2-production catalytic activity on TiO_2-supported Pt nanoparticles(Pt NPs).Two different types of surface Pt sites,tip Pt(Pt_(tip)) and edge/terrace Pt_(edge/terrace),on TiO_2-supported Pt nanoparticles(Pt NPs) were identified.The photocatalytic H2-production activity of TiO_2-supported Pt NPs shows a linear functional relationship with the number of Pt_(tip) sites.However,the number of Pt_(edge/terracesites) produced little effect on the activity of TiO_2-supported Pt NPs.First-principle simulations confirmed that H2-evolution at the Pttipsites owns a lower energy barrier than that at Pt_(edge/terrace).This findings would be helpful for the fabrication of high-performance Pt catalysts.  相似文献   

7.
TiO2广泛用作半导体光催化材料, 但由于自身对光利用率低(只吸收紫外光)、禁带宽度较大、光生载流子复合率极高, 限制了它在相关领域的应用. 为此, 设计了Ti3+离子自掺杂来克服TiO2半导体材料的上述缺点, 进而提高其光催化活性. 在不引入其他元素的情况下, 以TiOF2为原料, Zn粉为还原剂, 在水热条件下采用拓扑相变法原位制备了具有可见光响应的Ti3+自掺杂空盒状TiO2(记为Ti3+/TiO2)催化剂材料. 掺杂金属离子可以改变半导体TiO2的结晶度和产生晶格缺陷, 形成电子或空穴的捕获中心, 影响电子-空穴对的复合; 同时, 掺杂金属离子产生的晶格缺陷有利于Ti3+和氧空位的形成, 有利于提高TiO2的量子效率. Ti3+掺杂是一种既清洁又未引入其他金属离子的掺杂改性方法, 它能有效保持催化剂的结构和形貌不受其他金属离子的影响. 总之, 金属离子掺杂有效拓展了TiO2的光吸收范围, 并极大地提高了TiO2的光催化活性.本文研究了不同量的还原剂对催化剂空盒状TiO2结构形貌影响, 以及在可见光下光催化降解罗丹明B反应性能, 发现Ti3+/TiO2催化剂均拥有非常好的光催化活性, 其中R0.25催化剂在可见光下120 min, RhB降解率达到96%, 是TiO2的4倍多. 且可循环使用5次的光催化循环降解实验后, 表现出较高的稳定性. 催化剂经过Ti3+自掺杂后, 对催化剂自身的空盒状结构形貌并无很大的影响, 随着还原剂Zn粉的量增加, Ti4+还原形成Ti3+数量增加, 导致形成更多的氧空位. 皆为锐钛矿型TiO2,与未掺杂Ti3+的TiO2比较发现, 自掺杂Ti3+的TiO2的(105)XRD衍射峰越来越尖锐, (004)衍射峰越来越宽. 随着还原剂Zn粉质量的逐渐增加, 催化剂的光响应范围拓宽到可见光区, 且逐渐增强. 这说明Ti3+的掺杂不仅提高了TiO2在可见光的响应能力, 也提高了TiO2在紫外光范围的响应能力. 另外, 掺杂后的TiO2禁带宽度的减小, 使其价带上的电子更容易被可见光激发, 产生更多的电子-空穴对参与光催化反应, 从而提高TiO2的光催化效率.  相似文献   

8.
采用水热法制备了富含(001)晶面的锐钛矿型TiO2纳米片,并通过改变热处理过程中NH3流速制备不同N掺杂浓度的TiO2纳米片.运用X射线衍射、场发射扫描电镜、高分辨率透射电子显微镜、紫外-可见漫反射光谱、X射线光电子能谱和荧光光谱对光催化剂进行了结构和性能表征,并以罗丹明B为目标降解物,考察了N掺杂浓度对TiO2纳米片可见光催化活性的影响.结果表明,NH3流速为40ml/min时制备的N掺杂TiO2纳米片具有最低的光生电子-空穴复合速率,最高的OH产生能力并表现出最高的光催化活性.同时,讨论了N掺杂浓度对TiO纳米片可见光催化活性影响的机理.  相似文献   

9.
Herein, we have demonstrated that the electrospun nanofibers of TiO(2)/CdS heteroarchitectures could be fabricated through combining electrospinning technique with hydrothermal process. The configuration, crystal structure, and element composition of the as-prepared TiO(2)/CdS heteroarchitectures were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), resonant Raman spectrometer, X-ray photoelectron spectroscopy (XPS). The results indicated that the high-density hexagonal wurtzite CdS crystalline particles of ca. 6-40 nm in diameter were uniformly and closely grown on anatase TiO(2) nanofibers. Especially, the light-absorption properties as well as photocatalytic characteristics of pure TiO(2) nanofibers and TiO(2)/CdS heteroarchitectures with different amount loading of CdS were also investigated. The absorption of TiO(2)/CdS heteroarchitectures was extended to the visible due to effective immobilization of sensitizing agent CdS on TiO(2). In contrast with the pure TiO(2) nanofibers, the TiO(2)/CdS heteroarchitectures showed excellent photocatalytic activity by using rhodamine B dye as a model organic substrate under visible-light irradiation. It was worth noting that the cooperative photocatalytic mechanism of the TiO(2)/CdS heteroarchitectures was also discussed.  相似文献   

10.
Ultrathin TiO2 nanosheets with coexposed {001}/{101} facets have attracted considerable attention because of their high photocatalytic activity. However, the charge-separated states in the TiO2 nanosheets must be extended to further enhance their photocatalytic activity for H2 evolution. Herein, we present a successful attempt to selectively dope lanthanide ions into the {101} facets of ultrathin TiO2 nanosheets with coexposed {001}/{101} facets through a facile one-step solvothermal method. The lanthanide doping slightly extended the light-harvesting region and markedly improved the charge-separated states of the TiO2 nanosheets as evidenced by UV-vis absorption and steady-state/transient photoluminescence spectra. Upon simulated sunlight irradiation, we observed a 4.2-fold enhancement in the photocatalytic H2 evolution activity of optimal Yb3+-doped TiO2 nanosheets compared to that of their undoped counterparts. Furthermore, when Pt nanoparticles were used as cocatalysts to reduce the H2 overpotential in this system, the photocatalytic activity enhancement factor increased to 8.5. By combining these results with those of control experiments, we confirmed that the extended charge-separated states play the main role in the enhancement of the photocatalytic H2 evolution activity of lanthanide-doped TiO2 nanosheets with coexposed {001}/{101} facets.  相似文献   

11.
A simple approach was proposed to synthesize three types of ellipsoidal hollow nanostructures whose shells are assembled from anatase TiO(2) nanosheets (NSs) with exposed (001) facets. Among them, ellipsoid Fe(3)O(4)@TiO(2)-NS nanorattles can be readily generated as a magnetically separable photocatalyst with enhanced activity through in situ reduction of the α-Fe(2)O(3) core.  相似文献   

12.
This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.  相似文献   

13.
利用溶胶-凝胶法制备了不同比率的CdS掺杂TiO2复合纳米颗粒催化剂,并用其进行了紫外光、日光灯和太阳光全波长光催化去除水中氨氮和其它形式无机氮的对比实验研究.考察了添加催化剂的量、CdS复合比率、有氧化态氮亚硝酸根或硝酸根与氨氮共存时光催化脱氮的耦合效果、外加光源等对脱除氨氮效率的影响,并研究了后3个因素对CdS光腐蚀程度的影响.对于氨氮初始质量浓度为50mg/L的模拟废水,在通空气搅拌条件下,n(CdS):n(TiO2)=0.17的CdS/TiO2催化剂脱氮效果最佳,此时经紫外光照2h后脱除氨氮效率达41.5%.实验结果表明:复合催化剂中CdS的含量是影响光催化活性和光腐蚀程度的重要因素.  相似文献   

14.
CdS modified mesoporous titania core-shell spheres (CdS/CS-TiO2) with enhanced visible-light activity were synthesized by an in situ method. This method included two steps: planting CdO into the framework of anatase TiO2 core-shell spheres and then converting it to CdS by ion-exchange. The physicochemical properties of the obtained samples were investigated by X-ray diffraction, scanning electron microscopy, transmission electronic micrograph, UV–vis diffuse reflectance spectra and nitrogen sorption. The in situ strategy resulted in CdS quantum dots highly dispersed in CS-TiO2 without destroying the mesoporous core-shell structure. Compared with CS-TiO2, the as-synthesized samples exhibited stronger visible-light absorption capability and greatly enhanced photocatalytic activity toward the degradation of Rhodamine B and 4-chlorophenol aqueous solution under visible light irradiation (λ > 420 nm).  相似文献   

15.
Well-faceted nanocrystals of anatase TiO(2) with specific reactive facets have attracted extraordinary research interest due to their many intrinsic shape-dependent properties. In this work, hierarchical TiO(2) microspheres consisting of anatase nanosheets or decahedrons were synthesized by means of a facile hydrothermal technique; meanwhile, the percentage of {001} facets can be tuned from 82 to 45%. Importantly, by investigating the photo-oxidation reactions for ˙OH radical generation and photoreduction reactions for hydrogen evolution, the TiO(2) microspheres consisting of nano-decahedrons with 45% {001} facets show superior photoreactivity (more than 4.8-times) compared to the nanosheets with 82% {001} facets. By analyzing the results of scanning electron microscopy (SEM), photoluminescence (PL) and first-principles density functional theory (DFT) calculations, a model of charge separation between the well-formed {001} and {101} facets is proposed, and the enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges among the crystal facets co-exposed.  相似文献   

16.
Anatase TiO(2) microspheres with controlled surface morphologies and exposed crystal facets were directly synthesized on metal titanium foil substrates by means of a facile, one-pot hydrothermal method without use of any templating reagent. The obtained products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelecron spectroscopy (XPS), and the focused ion beam (FIB) technique. The sizes of the resultant microspheres ranged from 1.1 to 2.1 μm. The transformation of anatase TiO(2) microspheres with exposed {001} facets surface to nanosheets surface with {101} facets was achieved by simply controlling the hydrothermal reaction time. The anatase TiO(2) microspheres with exposed square-shaped plane {001} facets were obtained by controlling the reaction time at 1 h. The prolonged reaction time transforms the anatase TiO(2) microspheres with exposed square-shaped plane {001} facets to eroded {001} facets then to a nanosheet surface with exposed {101} facets. With hydrothermal synthesis, the surface morphological structure and crystal facets formation are highly dependent on dissolution/deposition processes, which can be strongly influenced by attributes, such as pH of the reaction media, the total concentration of dissolved and suspended titanium species, and the concentration of fluoride in the reaction solution. The changes of these attributes during the hydrothermal process were therefore measured and used to illustrate the morphology and crystal-facet transformation processes of anatase TiO(2) microspheres. The surface morphologies and crystal-facet transformations during hydrothermal processes were found to be governed by the compositional changes of the reaction media, driven by dynamically shifted dissolution/deposition equilibria. The photocatalytic activities of the photoanodes made of anatase TiO(2) microspheres were evaluated. The experimental results demonstrated that the photocatalytic activity of anatase TiO(2) microspheres with exposed {001} facets was found to be 1.5 times higher than that of the anatase TiO(2) microspheres with exposed {101} facets.  相似文献   

17.
依次用溶剂热法和水热法制备得到暴露(101)晶面的八面双锥体二氧化钛OBP-TiO2和不同碳负载量的N-CDs/OBP-TiO2复合催化剂,以及暴露(001)晶面的纳米片二氧化钛TNS和不同碳负载量的N-CDs/TNS复合催化剂。利用TEM、XRD、XPS等表征手段对这2类复合催化剂的形貌结构、化学成分等作了鉴定。系统研究了碳量子点负载量对可见光降解RhB的光催化性能影响。实验发现,由于N-CDs的加入,均能较大提高2类复合催化剂的光催化性能。(101)高裸露晶面N-CDs/OBP-TiO2比(001)高裸露晶面N-CDs/TNS的光催化活性高。  相似文献   

18.
A new composite consisting of TiO(2) nanotubes and CdS nanoparticles, where CdS particles bind covalently to the titania surface through a bifunctional organic linker, was successfully fabricated; this titania nanotube-based composite shows enhanced photocatalytic activity under visible-light irradiation.  相似文献   

19.
采用简单的化学偏聚法合成出Ag3PO4纳米颗粒、磷酸钴(Co3(PO4)2,CoP)纳米片以及它们两者的纳米复合结构(CoP/Ag3PO4),同时还比较了它们的可见光催化活性.采用场发射扫描电镜(FESEM)、X射线衍射(XRD)、紫外-可见(UV-Vis)吸收光谱以及光致发光谱等手段对其形貌、结构、光学以及可见光催化性能等进行表征.结果表明,CoP/Ag3PO4复合纳米结构的可见光降解甲基橙(MO)的速率和循环稳定性均明显优于其它两种物质.这表明CoP应该起着共催化剂的作用,它能够抑制光生电子与空穴之间的复合,并且提供大量高活性的光生空穴.此外,我们还发现CoP/Ag3PO4降解另一种阳离子型染料——罗丹明B(RhB)的能力则远不如纯Ag3PO4,这可能是与光催化剂的表面性质发生改变有关,造成更低的RhB吸附能力.本文提供了一种廉价制备高效可见光催化剂的新方法.  相似文献   

20.
采用有机溶剂热法在FTO衬底上制备{001}面暴露的单晶锐钛矿相TiO2纳米片阵列,通过FESEM和XRD研究样品的形貌和晶体结构. 与水热法制备的纳米片阵列相比,有机溶剂热法制备的样品取向性更好. 采用光沉积方法在纳米片阵列上沉积Pt,所得到的Pt纳米颗粒粒径更为均匀,并且更容易沉积在{001}面上. 所负载的Pt 纳米颗粒增强了TiO2纳米片的光吸收性能,同时大大减弱了光致发光强度. 在光催化性能测试中,具有最优负载量的样品催化性能提高了一倍. 与传统的Pt负载相比,{001}面的最优负载量显得相当小,这可能源于高活性{001}面的原子结构.  相似文献   

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