【作者】 于耀光；

【导师】 陈刚；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2014， 博士

【摘要】 利用一种既不释放温室气体，也不产生其它污染物的方式来为世界提供能源是一项极具挑战的课题，而通过半导体光催化剂分解水制氢无疑是最吸引人的手段之一。在众多的光催化材料中，以ZnS及CdS为代表的硫化物光催化剂因其优异的光催化制氢性能受到了研究者的广泛关注，在此领域的研究也取得了很多深受瞩目的成果。本论文利用简单方法合成了一系列具有优异光催化制氢性能的锌镉基硫化物光催化材料，系统的研究了晶体结构、微观形貌、光生电荷分离与光催化制氢性能之间的关系。采用水热法首次合成了具有分级多孔结构的Cd、In共掺ZnS光催化剂，其BET比表面积最高可达127m2·g1。FESEM及TEM测试结果表明光催化剂是由纳米片随机自组装的花状微球构成，通过调节Cd与In的含量可使Cd，In共掺ZnS纳米片的晶体生长过程处于奥斯特瓦尔德熟化与侧向定向聚集晶体生长机制的竞争中，从而使得纳米片具有六方纤锌矿/立方闪锌矿异质结构，该异质结构对光生电子空穴分离具有促进作用。Cd，In共掺ZnS光催化剂对可见光的吸收主要源于Cd元素的掺杂。负载2wt%Pt的Cd，In共掺ZnS光催化剂的制氢活性最高可达3.7mmol·h1，是一种具有潜在应用价值的光催化材料。采用水热法合成了ZnIn2S4/CdIn2S4复合光催化剂，ZnIn2S4与CdIn2S4的形貌分别对应于纳米片紧密堆积的大花球与纳米片松散堆积的小花球。由于Cd与Zn在ZnIn2S4与CdIn2S4间的交互掺杂，复合光催化剂紫外可见吸收光谱的吸收边集中在540550nm范围内。通过在ZnIn2S4/CdIn2S4复合光催化剂中引入还原助催化Pt及氧化助催化剂PdS，确定了光催化制氢过程中的速度控制步骤为光催化氧化半反应。负载PdS助催化剂后的复合光催化剂的光催化制氢活性最高可达780μmol·h1，相比于纯相ZnIn2S4光催化剂性能提高近3倍。通过简便、快捷的微波辅助液相法合成了一系列CdxZn1xS固溶体光催化剂，15min内便能完成反应过程。所制备的光催化剂是由纳米晶团聚而成的无规则二次颗粒。通过在反应过程中引入阴离子表面活性剂十二烷基苯磺酸钠(SDBS)，使得所制备的纳米晶具有孪晶结构，纳米晶中的孪晶结构可使光生电子空穴有效地分离。当SDBS浓度为0.6mol·L1时，所合成的Cd0.6Zn0.4S固溶体光催化剂无负载条件下制氢活性亦可达3.6mmol·h1。根据以纳米晶团聚而成的Cd0.6Zn0.4S光催化剂在首次循环后活性升高的现象，首次提出了聚集体系光催化剂初始反应阶段的“活化机制”，为合理评价聚集体系光催化剂的制氢性能提供了理论依据。通过溶剂热法首次将La掺入Cd0.6Zn0.4S固溶体的空间电荷层中，Mott–Schottky测试表明调节La的掺入量可调控Cd0.6Zn0.4S固溶体空间电荷层的厚度，XPS测试结果表明La原子以La–S–Zn键的形式存在。由于La的掺杂，Cd0.6Zn0.4S固溶体对光的吸收明显增强，350nm单色光下CZS:2%La的表观量子产率高达93.3%。而CZS:2%La光催化剂在模拟太阳光(AM1.5)的可见波段下的制氢活性最高可达1.39mmol·h1。此外，La修饰对光催化分解水制氢的促进作用在红色TiO2体系中也得到了验证。更多还原

【Abstract】 Powering the world without emitting greenhouse gases or producing additional pollutants is a challenging issue. Photocatalytic H2evolution through solar water splitting using semiconductor photocatalyst is one of the most attractive routes to achieve this goal. Among the photocatalysts, sulfide photocatalysts, including ZnS, CdS, received much attention because of their outstanding performance for photocatalytic H2production. Research in this field have received remarkable achievements. In this thesis, a series of Zinc-and Cadmium-based sulfide photocatalytic materials have been synthesized through facile routes. The relationship between crystal structure, morphology, separation of photo-generated charges and performance of photocatalytic H2production has been investigated systematically.Hierarchical porous Cd, In co-doped ZnS photocatalyst was firstly synthesized through the hydrothermal method. BET specific surface area of the as-prepared samples was up to127m2·g1. FESEM and TEM results demonstrated that the photocatalysts were composed of flower-like microsphere by assembly of nanoflakes. By adjusting the amount of Cd and In components in Cd, In co-doped ZnS photocatalyst, the crystal growth process would be in a competition between Ostwald ripening and orientation attachment, which makes the nanoflakes present wurtzite/sphalerite heterostructures. The wurtzite/sphalerite heterostructures could contribute to the separation of photo-generated charges. The visible-light absorption was mainly attributed to the doping of Cd element. Performance of photocatalyst with2%Pt loaded for photocatalytic H2production reached3.7mmol·h1, which is a good candidate for potential applications.ZnIn2S4/CdIn2S4composite photocatalysts were synthesized through hydrothermal method. Morphologies of ZnIn2S4and CdIn2S4corresponding to bigger flower-like microspheres with denser packed nanoflakes and smaller flower-like microspheres with looser packed nanoflakes. Due to the cross-doping of Cd and Zn into the ZnIn2S4and CdIn2S4, the absorption edges of composite photocatalysts were mainly located between540and550nm. Through introducing the Pt reduction cocatalyst and PdS oxidation cocatalyst into the ZnIn2S4/CdIn2S4composite photocatalyst, the rate-determining step of the total photocatalytic hydrogen evolution reaction was confirmed to the photocatalytic oxidative half reaction. Performance of the composite photocatalyst for photocatalytic H2production could reach780μmol·h1after loading PdS cocatalyst, which is3times higher than the pure ZnIn2S4photocatalyst.A series of CdxZn1xS solid solution photocatalysts have been synthesized through a facile, fast microwave-assisted route, the photocatalyst powder could be obtained in15min. The as-prepared photocatalyst was composed of irregular secondary particles by assembly of nanocrystals. Through introducing sodium dodecyl benzene sulfonate (SDBS) as the anionic surfactant, the nanocrystals presented twin structures which could effectively separate the photo-generated electrons and holes. The photocatalytic H2production performance of Cd0.6Zn0.4S solid solution photocatalyst synthesized in the presence of0.6mol·L1of SDBS reached3.6mmol·h1even without loading any cocatalyst. According to the phenomenon that the performance of Cd0.6Zn0.4S photocatalyst composed of nanocrystals increased after first cycle, an “activation effect” of the photocatalyst in assemble system at the initial stage of photocatalytic reaction was proposed, which provides theoretical evidence for the rational evaluation of the photocatalytic hydrogen evolution performance of the photocatalysts in assemble system.La was firstly doped into the space charge layer of Cd0.6Zn0.4S solid solution through solvothermal method. Mott–Schottky test indicated the depth of space charge layer of Cd0.6Zn0.4S solid solution could be adjusted by changing the amount of La doped. XPS results demonstrated La was doped into the space charge layer in the form of La–S–Zn bonds. Attributed to the La doping, light-absorbing property of Cd0.6Zn0.4S solid solution was greatly improved. Furthermore, the apparent quantum yield of CZS:2%La was up to93.3%under the irradiation of350nm monochromatic light. And the photocatalytic performance for H2production of CZS:2%La photocatalyst under the irradiation of the visible region of simulated sunlight (AM1.5) could reach1.39mmol·h1. Moreover, the promotion of La modification on the photocatalytic H2production performance has also been verified in the red TiO2system.更多还原