兰州大学机构库 >化学化工学院
ZnIn2S4基光催化剂的结构调控及析氢性能研究
Alternative TitleStructural regulation and hydrogen evolution performance of ZnIn2S4-based photocatalysts
范会涛
Subtype博士
Thesis Advisor刘伟生
2023-09-02
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学博士
Degree Discipline化学
Keyword光催化制氢 photocatalytic hydrogen evolution ZnIn2S4 ZnIn2S4 结构调控 structural regulation 掺杂 doping 异质结 heterojunction
Abstract

通过光解水技术将太阳能转化为低密度、零污染的氢能是解决能源危机和环境污染这两大问题的有效途径。开发绿色、高效的光催化剂是实现太阳能向氢能转换的关键。层状结构的ZnIn2S4(ZIS)因具有合适的带隙(2.06-2.85 eV)、物理化学性质稳定、形貌可控、电子结构可调等优点,是最具潜力的析氢候选光催化剂之一。然而,单体ZIS存在易团聚、可见光吸收范围窄、光生载流子分离效率低、氧化还原能力弱等缺点,严重限制了其在光催化领域的发展及广泛应用。针对上述存在的问题,本论文通过元素掺杂、构建异质结、微观形貌调控等策略对ZIS进行改性和优化,实现了光催化性能的有效提升。通过实验技术分析与理论计算相结合的方式研究了不同光催化体系的析氢性能提升机理。具体研究内容如下:

(1)以一维(1D)MoO3纳米带作为模板和Mo源,通过溶剂热法成功合成了Mo原位掺杂ZIS中空分级纳米管光催化剂(ZNT-Mox),实现了微观形貌和元素掺杂对ZIS的同步调控。制备的管状Mo掺杂ZIS光催化剂展现出优异的光催化析氢性能,最佳Mo掺杂含量样品(ZNT-Mo5)的光催化析氢速率为12.10 mmol h-1 g-1,大约是单体ZIS(2.58 mmol h-1 g-1)的4.7倍。其优异的光催化析氢性能可归因于以下三个方面:①高的比表面积和丰富的孔结构为光催化反应提供了更多的吸附和反应位点;②Mo掺杂调控了ZIS的电子结构和能带结构,有效缩短了带隙,拓宽了可见光吸收范围;③高导带电位为光催化析氢反应提供了强的驱动力。

(2)采用微观形貌和组分共调控策略,以十四面体介孔Ce-MOF作为掺杂剂和模板,通过一步溶剂热法合成了原位Ce掺杂ZIS十四面体分级纳米笼光催化剂(ZTNs-Cex)。独特的三维(3D)中空结构有效增大了光催化剂的比表面积,缩短了光生载流子从体相到表面的垂直迁移距离。通过实验表征技术与密度泛函理论(Density Functional Theory,DFT)计算,揭示了Ce掺杂增加了ZIS价带附近的电子态密度,可以提供更多的光生载流子参与光催化反应。此外,Ce掺杂使ZIS的带隙变窄,扩大了可见光吸收范围。经过组分优化和微观形貌调控,最佳Ce掺杂含量纳米笼光催化剂(ZTNs-Ce20)的析氢速率达到7.46 mmol h-1 g-1,远高于单体ZIS(2.61 mmol h-1 g-1),并表现出良好的循环稳定性。

(3)p型半导体CuS具有较窄的带隙,对可见光有较强的吸收能力,可作为ZIS的助催化剂进而提高其光催化析氢性能。因此,本工作采用模板法合成了由二维(2D)CuS纳米片组装的立方分级纳米笼。然后在立方纳米笼的表面生长n型2D ZIS纳米片,成功合成了分级2D/2D CuS@ZIS纳米笼。CuS纳米笼的引入不仅有效提升了复合光催化剂的可见光吸收能力而且增大了比表面积。结合实验表征技术与DFT计算揭示了CuS和ZIS p-n异质结界面处强电子相互作用形成的内建电场是光生载流子分离和迁移的强大驱动力。经过微观形貌调控和界面优化,3%-CuS@ZIS复合光催化剂表现出优异的光催化析氢性能,其析氢速率为7.91 mmol h-1 g-1,约为单体ZIS(2.63 mmol h-1 g-1)的3倍。

(4)在由超小Co3O4纳米粒子(Nanoparticles,NPs)组装的分级纳米盒表面生长ZIS纳米片,成功制备了0D/2D Co3O4@ZIS分级纳米盒(Nanoboxes,NBs)异质结复合光催化剂(CZ-x NBs)。引入由Co3O4 NPs有序组装而成的3D 纳米盒,不仅显著提高了催化剂的比表面积,还有效拓宽了催化剂的可见光吸收范围。结合实验技术分析和DFT理论计算揭示了Co3O4@ZIS 0D/2D异质结的S型电荷转移机制。在内建电场和库仑力的作用下,光生载流子的分离和迁移效率得到了显著提高,同时保留了光生电子的强还原性。优化后的复合光催化剂(CZ-5 NBs)在可见光照射下展现出优异的光催化析氢性能,其析氢速率为39.38 mmol h-1 g-1,约为单体ZIS的12.9倍。在经历4次循环实验后,光催化析氢活性仍然能保持82.8%,具有很好的光催化稳定性。此外,本工作为构建新型中空0D/2D异质结纳米复合材料提供了一种有效的合成策略。

Other Abstract

The conversion of solar energy into low-density and zero-pollution hydrogen energy through photocatalytic water splitting technology is an effective way to solve the two major problems of energy crisis and environment pollution. The development of green and efficient photocatalysts is the key to realize the conversion of solar energy to hydrogen energy. ZnIn2S4 (ZIS) with layered structure is one of the most promising photocatalysts for hydrogen evolution due to its suitable band gap (2.06- 2.85 eV), stable physical and chemical properties, controllable morphology and adjustable electronic structure. However, the monomer ZIS has the shortcomings of easy aggregation, narrow visible light absorption range, low separation efficiency of photogenerated carriers, and weak redox ability, which seriously limits its development and wide application in the field of photocatalysis. In view of the above problems, we modified and optimized ZIS through strategies such as element doping, construction of heterojunctions, and micro-morphology control, thereby achieved an effective improvement in photocatalytic performance. The mechanism of hydrogen evolution performance improvement of different photocatalytic systems was studied by combining experimental technical analysis with theoretical calculation. The following are the specific research contents:

(1) Mo in-situ doped ZIS hollow hierarchical nanotube photocatalyst (ZNT-Mox) was successfully synthesized by solvothermal method using one-dimensional (1D) MoO3 nanobelts as template and Mo source, and the synchronous regulation of micro-morphology and element doping on ZIS was realized. The prepared tubular Mo-doped ZIS photocatalyst exhibits excellent photocatalytic hydrogen evolution performance. The photocatalytic hydrogen evolution rate of the sample with the best Mo doping content (ZNT-Mo5) is 12.10 mmol h-1 g-1, which is about 4.7 times that of the monomer ZIS (2.58 mmol h-1 g-1). Its excellent photocatalytic hydrogen evolution performance is attributed to the following three aspects: ①High specific surface area and abundant pore structure provide more adsorption and reaction sites for photocatalytic reactions; ②Mo doping regulates the electronic structure and band structure of ZIS, effectively shortens the band gap, and broadens the visible light absorption range; ③High conduction band potential provides a strong driving force for photocatalytic hydrogen evolution reaction.

(2) Using a co-regulation strategy of micro-morphology and composition, the in-situ Ce-doped ZIS hierarchical nanocage photocatalyst (ZTNs-Cex) was synthesized by one-step solvothermal method using tetrakaidecahedron mesoporous Ce-MOF as dopant and template. The unique three-dimensional (3D) hollow structure effectively increases the specific surface area of the photocatalyst, and shortens the vertical migration distance of photogenerated carriers from bulk to surface. Through experimental characterization techniques and density functional theory (DFT) calculations, it is revealed that Ce doping increases the density of electronic states near the valence band of ZIS, thus providing more photogenerated carriers to participate in photocatalytic reactions. Moreover, Ce doping narrows the band gap of ZIS, thereby expanding its visible light absorption range. After component optimization and micro-morphology control, the hydrogen evolution rate of the nanocage photocatalyst (ZTNs-Ce20) with the optimal Ce doping content reached 7.46 mmol h-1 g-1, which was much higher than that of the monomer ZIS (2.61 mmol h-1 g-1), and showed good cycle stability.

(3) The p-type semiconductor CuS has a narrow band gap and strong absorption capacity for visible light, which can be used as a cocatalyst for ZIS to improve its photocatalytic hydrogen evolution performance. Therefore, in this work, cubic hierarchical nanocages assembled by two-dimensional (2D) CuS nanosheets were synthesized by template method. Then, n-type 2D ZIS nanosheets were grown on the surface of cubic nanocages, and hierarchical 2D/2D CuS@ZIS nanocages were successfully synthesized. The introduction of CuS nanocages not only effectively improves the visible light absorption capacity of the composite photocatalyst but also increases the specific surface area. Combined with experimental characterization techniques and DFT calculations, it is revealed that the built-in electric field formed by strong electron interaction at the interface of CuS and ZIS p-n heterojunctions is a powerful driving force for the separation and migration of photogenerated carriers. After micro-morphology control and interface optimization, the 3%-CuS@ZIS composite photocatalyst exhibits excellent photocatalytic hydrogen evolution performance, and its photocatalytic hydrogen evolution rate is 7.91 mmol h-1 g-1, which is about 3 times that of monomer ZIS (2.63 mmol h-1 g-1).

(4) The 0D/2D Co3O4@ZIS hierarchical nanoboxes (NBs) heterojunction composite photocatalyst (CZ-x NBs) was successfully prepared by growing ZIS nanosheets on the surface of hierarchical nanoboxes assembled by ultra-small Co3O4 nanoparticles (NPs). The introduction of 3D nanoboxes assembled by Co3O4 NPs not only significantly increases the specific surface area of the catalyst, but also effectively broadens the visible light absorption range of the catalyst. The S-scheme charge transfer mechanism of Co3O4@ZIS 0D/2D heterojunction was revealed by combining experimental technical analysis and DFT calculation. Under the action of built-in electric field and Coulomb force, the separation and migration efficiency of photogenerated carriers has been significantly improved, while retaining the strong reducibility of photogenerated electrons. The optimized composite photocatalyst (CZ-5 NBs) exhibits an efficient photocatalytic hydrogen evolution performance under visible light irradiation, and its hydrogen evolution rate is 39.38 mmol h-1 g-1, which is about 12.9 times that of monomer ZIS. After four cycles of experiments, the photocatalytic hydrogen evolution activity can still maintain 82.8%, with good photocatalytic stability. Moreover, this work provides an effective synthesis strategy for constructing novel hollow 0D/2D heterojunction nanocomposites.

Subject Area光催化
MOST Discipline Catalogue理学 - 化学 - 无机化学
URL查看原文
Language中文
Other Code262010_120190903001
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/538075
Collection化学化工学院
Affiliation
兰州大学化学化工学院
Recommended Citation
GB/T 7714
范会涛. ZnIn2S4基光催化剂的结构调控及析氢性能研究[D]. 兰州. 兰州大学,2023.
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