In2O3/CuO纳米异质结的制备和光催化性质研究

通过溶胶-凝胶结合静电纺丝过程制备了In₂O₃/CuO纳米异质结。XRD和Raman光谱的研究表明,随着前驱物中Cu/In比例的增加,CuO相的含量逐渐增加。吸收光谱研究表明,随着CuO含量的增加,复合纳米结构的可见光吸收明显增强。光催化实验研究结果表明,In₂O₃/CuO纳米异质结具有比单一相的In₂O₃和CuO更强的光催化性能,其主要来源于异质结所导致的增强的光生电子和空穴的分离效率。     

单原子Bi吸附对BiOI光催化性能的影响

BiOI是一种极具潜力的光催化剂,目前其光催化效率较低,有待进一步提高.本文为了研究其微观光催化机理,提高光催化性能,采用第一性原理方法计算研究单原子Bi吸附在1I-BiOI表面体系的结构、电子和光学性质.与BiOI相比,Bi/BiOI吸附体系不仅结构稳定性强,而且具有可见光吸收高的性质.计算结果表明,单原子Bi吸附在1I-BiOI表面时,电荷从吸附原子Bi转移到1I-BiOI表面,与1I-BiOI体系相比,吸附Bi的1I-BiOI体系中Bi-B、Bi-Z和Bi-H的功函数降低,单原子Bi吸附后,Bi/BiOI体系的光吸收增强.表明吸附原子Bi与1I-BiOI之间形成了内建电场,提高了电子转移效率,抑制了光电子-空穴复合率,进而提高光催化性能.计算研究表明单原子Bi吸附能提高BiOI光催化效率,有助于设计具有更好光催化性能的新型结构.     

钙钛矿铁电半导体的光催化研究现状及其展望

钙钛矿材料可以分为ABO_3氧化物和或I)卤化物两大类,它们都具有丰富的物理性质和优异的光电性能,比如铁电性和光催化性能.本文介绍了和等铁电半导体光催化材料和异质结的制备方法,总结了它们在光电催化方面的研究进展.目前研究者已经针对氧化物光催化材料做了各种研究,包括:降低吸光层铁电材料的带隙,制备铁电/窄带半导体吸光层异质结,制备比表面积很大的纳米片、纳米棒或者其他纳米结构,以便吸收更多可见光;让铁电极化及其退极化场垂直于光催化工作电极表面,通过铁电/半导体异质结能带弯曲提供内电场,通过外电场进行光电催化,从而通过内、外电场高效分离光生-电子空穴对;通过光催化或者光电催化降解染料、分解水制氢、将CO2转换为燃料;通过铁电、热释电和压电协同效应提高催化效应和能量转换效率等卤素钙钛矿具有优异的半导体性质,其铁电性可能是引起超长的少数载流子寿命和载流子扩散长度的原因.通过优化光催化多层膜结构并添加防止电解液渗透的封装层可以避免被电解液分解,从而制备了具有很高能量转换效率的光电催化结构.最后,我们分析和比较了这些钙钛矿铁电半导体在光电催化领域面临的挑战,并展望了其应用前景.     

电场对GaN/g-C3N4异质结电子结构和光学性质影响的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法研究了GaN/g-C₃N₄异质结的稳定性、电子结构、光学性质及功函数,同时考虑了电场效应.结果表明:GaN/g-C₃N₄范德瓦耳斯异质结的晶格失配率(0.9%)和晶格失配能极低(-1.230 meV/?~2,1?=0.1 nm),说明该异质结稳定性很好,且该异质结在很大程度上保留了GaN和g-C₃N₄的基本电子性质,可作为直接带隙半导体材料.同时,GaN/g-C₃N₄异质结在界面处形成了从GaN指向g-C₃N₄的内建电场,使得光生电子-空穴对可以有效分离,这有利于提高体系的光催化能力.进一步分析可知,外加电场使GaN/g-C₃N₄异质结的禁带宽度有着不同程度的减小,使得电子从价带跃迁至导带更加容易,有利于提高体系的光催化活性;此外,当外加电场高于0.3 V/A以及低于-0.4 ...     

水热法制备In2O3/ZnO异质结及其高的光催化性能

采用简单的两步水热法合成了不同In₂O₃质量比的In₂O₃/ZnO异质结复合材料．通过X射线衍射仪(XRD)、紫外-可见分光光度计(UV-vis)和扫描电子显微镜(SEM)对复合材料的结构、形貌和性能进行了表征．同时还使用UV-vis分光光度计测试了异质结降解罗丹明B(RhB)的光催化活性．实验结果表明,与纯ZnO和In₂O₃相比,In₂O₃的引入将ZnO的吸收光谱扩展到可见光区域,从而提高了其光生电子和空穴的分离．此外,In₂O₃/ZnO异质结在可见光照射对RhB具有较高的光催化活性．5 wt%-In₂O₃/ZnO异质结对RhB的降解率为84.3%,且具有良好的光催化稳定性．In₂O₃/ZnO异质结复合材料在有机染料废水的降解中有更广阔的应用前景．     

BiOCl1-xIx及BiOBr1-xIx固体溶液的制备、表征及性能研究

在太阳光照射下,利用半导体光催化去除污染物是最绿色、有效的方法之一,其核心问题是获得高效光催化剂。目前研究最多的光催化剂是TiO₂和ZnO等,但由于其禁带宽度大故不能充分利用太阳光,从而限制了其实际使用。除了对TiO₂等改性以改进其可见光催化活性外,开发其他材料作为光催化剂也是解决的重要途径。铋基化合物半导体由于原材料丰富、种类多、太阳光响应性好及优良的光催化活性而成为重要研究对象。其中卤氧铋系化合物[BiOX, X=Cl, Br, I]由于层状结构特点而具有良好的光催化活性,但单独使用时光催化效率较低。研究表明,BiOX间能通过形成固体溶液(即彼此呈分子分散的固体混合物)进一步改善其光催化降解污染物的能力。本文利用低温湿化学法,以Bi₂O₃为铋源,在醋酸溶液中加入一定比例的KI/KBr或KI/KCl水溶液,室温下反应0.5 h,分别得到片状结构的BiOCl_1-xI_x和BiOBr_1-xI_x固体溶液。X射线衍射(X-ray diffraction, XRD)分析结果表明,所合成的BiOCl_1-xI_x和BiOBr_1-xI_x样品结晶性良好,且能在x=0～1的范围内形成固体溶液。透射电子显微镜(transmission electron microscope, TEM)测得所制备的固体溶液呈不规则的薄片状。X射线光电子能谱(X-ray photoelectron spectroscopy, XPS)测试进一步证明了其表面元素组成及化学状态。紫外-可见漫反射光谱(diffuse reflectance spectroscopy, DRS)分析表明,随着碘元素含量的增加,固体溶液的吸收边界发生红移、禁带宽度减小,故可见光吸收能力增强、产生的载流子数目将增加。在可见光激发下对甲基橙(methyl orange, MO)降解的光催化性能研究表明,BiOCl_0.25I_0.75及BiOBr_0.25I_0.75拥有最高的光催化活性。循环实验表明,BiOCl_0.25I_0.75及BiOBr_0.25I_0.75都具有较高稳定性。光催化机理研究发现,这些卤氧铋样品光催化降解MO过程中的活性物种主要为空穴和超氧离子自由基。结合其能带结构,认为固体溶液的形成不但增加了可见光吸收能力,而且调变了其能带结构,相对于BiOI而言,固体溶液的形成降低了价带电位,提高了导带电位,因而增强了光生电子的还原能力及空穴的氧化能力,故催化性能提高。该工作的创新之处在于：采用的固体溶液制备方法,避免了高温水热法或加入表面活性剂等,而且所制备的BiOCl_1-xI_x和BiOBr_1-xI_x固体溶液,尤其是BiOCl_0.25I_0.75和BiOBr_0.25I_0.75,在可见光激发下对MO具有良好的降解能力,且催化剂的重复使用及稳定性良好,有望在环境治理中得到应用。     

SO2-4/CeO2-TiO2光催化材料的制备与光谱表征

采用溶胶-凝胶法结合硫酸浸渍法制备了SO2-4/CeO2-TiO2复合氧化物.利用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、吡啶吸附红外光谱(Py-FTIR)、紫外-可见光漫反射光谱(UV-Vis)、X射线光电子能谱价带谱(VB-XPS)及荧光光谱(PL)技术对样品的结构、性质进行了表征,以光催化分解水制氢为模型反应,评价了样品的光催化性能.XRD,FTIR结合PL结果表明CeO2与TiO2的复合形成了异质结构,有利于提高光生电子与光生空穴的分离效率,对催化剂活性的提高有促进作用;Py-FTIR谱图证明SO2-4/CeO2-TiO2复合氧化物在表面具有Lewis酸性,Lewis酸性位的产生是由于SO2-4在样品表面的配位吸附所致,S O— 的诱导效应增强了表面金属得电子能力,从而进一步提升光生载流子的分离效率;UV-Vis及XPS价带谱分析说明,半导体氧化物复合能够缩减带隙,拓宽光响应范围,Lewis酸性影响复合氧化物的能带结构,使其导带底位置向负向移动,利于光催化还原能力的提高,进而促进其光催化制氢活性.光催化分解水制氢实验结果表明,SO2-4/CeO2-TiO2复合氧化物具有优于纯氧化物CeO2,TiO2及未经硫酸浸渍的CeO2-TiO2复合氧化物的催化活性,5 h的产氢速率为1934.1μmol·g-1·h-1.光谱分析结果结合光催化制氢活性评价结果表明,SO2-4/CeO2-TiO2复合氧化物的异质结构与酸浸渍是影响样品光催化性能的主要因素.     

钙钛矿CsPbX3(X=Cl,Br,I)与五环石墨烯范德瓦耳斯异质结的界面相互作用和光电性能的第一性原理研究

异质结工程是一种提高半导体材料光电性能的有效方法.本文构建了全无机钙钛矿CsPbX₃(X=Cl,Br,I)和二维五环石墨烯penta-graphene(PG)的新型范德瓦耳斯(vdW)异质结,利用第一性原理研究了CsPbX₃-PG异质结不同界面接触的稳定性,进而计算了稳定性较好的Pb-X接触界面异质结的电子结构和光电性能.研究结果表明,CsPbX₃-PG(X=Cl,Br,I)异质结具有II型能带排列特征,能级差距由Cl向I逐渐缩小,具有良好的光生载流子分离能力和电荷输运性质.此外,研究发现CsPbX₃-PG异质结能有效拓宽材料的光吸收谱范围,并能显著提高其光吸收能力,尤其是CsPbI₃具有最优的光吸收性能.经理论估算,CsPbX₃-PG的光电功率转换效率(PCE)可高达21%.这些结果表明,全无机金属卤化物钙钛矿CsPbX₃-PG异质结可以有效地提高半导体材料的光电性能,预期在光电转换器件中具有重要的应用潜力.     

光催化半导体Ag$lt;sub$gt;2$lt;/sub$gt;ZnSnS$lt;sub$gt;4$lt;/sub$gt;的第一性原理研究

通过基于密度泛函理论的第一性原理计算, 对光催化水解半导体Ag₂ZnSnS₄的改性方案做了理论研究. 在与同类化合物的带边位置比较后发现, Cu与Ge共掺杂能够在Ag₂ZnSnS₄中实现禁带宽度和带边位置的双重调节, 从而使其能带结构优化到光催化水解最为理想的状态. 另外, CuGaSe₂ 可与Ag₂ZnSnS₄形成type-Ⅱ型带阶结构, 制备它们的异质结同样可用于提升其光催化水解性能. 关键词： 光催化半导体 2ZnSnS₄')" href="#">Ag₂ZnSnS₄ 带阶 电子结构优化     

石墨烯/BiOI纳米复合物电子结构和光学性质的第一性原理模拟计算

光催化材料在解决能源短缺和环境污染等问题方面具有广泛的应用前景,本文通过构建BiOI纳米薄膜并将其与石墨烯复合起来,得到具有较高的比表面积和良好的光催化活性的纳米复合物光催化材料.采用基于密度泛函理论的第一性原理方法分别计算了单层和双层BiOI纳米片及其与石墨烯复合结构的电子结构和光学性质,并考虑了BiOI中的Bi,O,I三种空位缺陷对电子结构和光学特性的影响.计算结果表明,由于BiOI和石墨烯之间的相互作用,在石墨烯和BiOI界面处自发发生电荷转移,形成电子-空穴对,且石墨烯衬底可有效提高BiOI对可见光的光吸收,提高其光催化活性.对空位缺陷的计算表明,Bi空位缺陷可促进石墨烯和BiOI之间的电荷转移,形成更多的层间电子-空穴对;相反,O和I空位缺陷则抑制层间电荷转移,减少电子-空穴对的生成.     

Microemulsion synthesis, characterization of bismuth oxyiodine/titanium dioxide hybrid nanoparticles with outstanding photocatalytic performance under visible light irradiation

Reverse microemulsions, consisting of n-hexanol, Triton X-100, Cyclohexane and aqueous salt solutions, were used to synthesize BiOI, TiO₂ and BiOI/TiO₂ hybrid nanoparticles at room temperature. The particles had been characterized by X-ray powder diffraction, FT-IR spectra, TG-DSC analysis, nitrogen sorption, electron microscopy, and UV-vis diffuse reflectance spectroscopy. The photocatalytic properties of those particles were evaluated by degradation of methyl orange under visible light irradiation. The BiOI/TiO₂ composites showed about 5 times higher photocatalytic performances than BiOI when the mole ratio of BiOI to TiO₂ was 75%. The remarkable enhancement in the visible light photocatalytic activities of the BiOI/TiO₂ heterostructures could be first attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitated the transfer of the photoinduced carriers. Meanwhile, the heterojunction formed between BiOI and TiO₂ would further retard the recombination of photoinduced carriers. In addition, high degree of crystallization, bimodal porous structure, relative large specific surface area, and appropriate energy band gap have great contribution to the enhancement of photocatalytic performance.     

Roles of BiOCl(001) in face-to-faced BiOI(010)/BiOCl(001) heterojunction

In order to have an insight into the internal electric field (IEF) of BiOCl(001), we design a novel wide-spectrum responsive BiOI(010)/BiOCl(001) heterojunction composite by a facile method. The system could shield the photocatalysis of BiOCl(001) under visible light due to its large E_g (3.41 eV), thus specifying role of the BiOCl(001) in BiOI(010)/BiOCl(001). The XRD and TEM results show that the composites exhibit a coexistence of both tetragonal BiOI(010) and BiOCl(001) phases. The as-prepared BiOI(010)/BiOCl(001) samples exhibit higher BET surface area than those of BiOI(010) and BiOCl(001). The UV, visible, and simulated sunlight photocatalytic activities of composites for methyl orange (MO) were greatly enhanced compared to either pure BiOI(010) or BiOCl(001). Especially, under the visible light, an enhancement of photocatalytic activity (MO, acid fuchsin) was found for BiOI(010)/BiOCl(001), suggesting an IEF of BiOCl(001) plays a key role on the photo-generated carrier separation of BiOI(010). Specifying the IEF role of BiOCl(001) in BiOI(010)/BiOCl(001) is expected to inspire the further exploration, developing efficient photocatalysts with potential applications.     

Hierarchical nanostructured 3D flowerlike BiOX particles with excellent visible-light photocatalytic activity

BiOX (X = Cl, Br, and I) semiconductors were firstly prepared by a facile mixed solvent solvothermal route. Several characterization tools were employed to study the phase structures, morphologies, and optical properties of the samples. The in situ chemically mixed prepared BiOX particles with diameters 3.0–5.0 μm, fabricated by nanoplates in the thickness range of 5–18 nm, exhibited the highest visible-light photocatalytic activity among the as-prepared samples and Degussa P₂₅ for the degradation of Rhodamine B (RhB). This result can be due to the narrow bandgap, broad sunlight range, high electronic negativity, and efficient separation of photoinduced electron–hole pairs. Finally, a possible photocatalytic mechanism has been proposed.     

The photocatalytic mechanism of BiOI with oxygen vacancy and iodine self-doping

The photocatalytic mechanism of BiOI with an oxygen vacancy and iodine self-doping is investigated by studying their structural, electronic and optical properties. The results of the first-principle calculations indicate that the utilization of the visible light region is broadened, and thus the photocatalytic performance is improved, via introducing an oxygen vacancy or I dopant. Among them, I-Bi doped BiOI shows the best photocatalytic performance, and it is also the preferred one of the three structures due to its better stability. The occurrence of I-Bi or I-I interactions in the original double iodine layer along with the introduction of I dopant leads to a planar localization of the photocatalytic mechanism. Then it is expected that the photo-generated carriers will transfer to the catalyst surface more easily; the photocatalytic activity of BiOI relies on the planar localization to a great degree.     

Enhanced photocatalytic performance of TiO2 nanowires by substituting noble metal particles with reduced graphene oxide

Noble metal particles have been embedded in semiconductors to improve photocatalysis efficiently, but the high cost made this approach difficult to apply widely in industry. Herein titanium dioxide/reduced graphene oxide (TiO₂/rGO) nanowires in a core-shell structure were prepared. The physicochemical properties and photocatalytic performance of the specimen were characterized in comparison with TiO₂ and TiO₂/Pt nanowires. The rGO layer and Pt nanoparticles increased chemical states of the components, reduced bandgap energy of the nanowires, enhanced visible light absorption, improved conductance and capacitance significantly. The methylene blue as catalyzed by TiO₂/Pt and TiO₂/rGO nanowires was degraded to 7.9% and 8.4% in an hour, but retained 25.7% by the TiO₂ nanowires. The properties and function of TiO₂/rGO nanowires were close to those of TiO₂/Pt nanowires, while the rGO price was much lower than that of Pt, which was of great significance for the photocatalytic application of TiO₂ heterojunction materials in industry.     

SnO2量子点/石墨烯复合结构的合成及其光催化性能研究

本文以SnCl₄·5H₂O和氧化石墨烯为先驱物, 乙醇水溶液为溶剂, 采用一种简单的水热法一步合成了具有可见光催化活性的SnO₂量子点(约3–5 nm)与石墨烯复合结构, 利用透射电子显微镜(TEM), 高分辨透射电子显微镜(HRTEM), X射线衍射仪(XRD), 傅里叶变换红外光谱(FT-IR)等技术对其结构进行了表征, 利用紫外可见吸收光谱(UV-vis)分析了其光学性能, 罗丹明-B染料为目标降解物研究了SnO₂量子点/石墨烯复合结构可见光催化性能. 结果表明: 与纯SnO₂、纯石墨烯相比, 复合结构显示出了很高的可见光催化活性. 通过对其结构进行分析, 我们提出了SnO₂量子点/石墨烯复合结构的形成机制及其可见光催化活性机理.     

Microwave-assisted synthesis of silver nanocrystals in benzyl alcohol and their subsequent in situ chemical transformation into Ag–AgCl nanohybrids for plasmonic photocatalysis

In heterostructured metal–semiconductor system, plasmonic metal nanostructures can cooperate with semiconductors to enhance the solar light harness and energy conversion. In this study, we report on the plasmonically photocatalytic system constructed by in situ growth of semiconductor on metal nanostructures with high performance and stability. A facile and rapid microwave-assisted route was first explored to synthesize Ag nanocrystals, and subsequently converting them to Ag–AgCl nanohybrids was realized by in situ chemical transformation strategy at room temperature. These Ag–AgCl nanohybrids were characterized by X-ray diffraction, scanning electronic microscopy, and UV–vis absorption spectroscopy. The resulting Ag–AgCl nanohybrids showed remarkable photocatalytic activity and excellent durability for the degradation of organic pollutants under visible light irradiation. This finding provides a new way to improve photocatalytic efficiency through controllable chemical transformation.