Photochemistry of metal cluster - GaN semiconductor hybrid materials

金属团簇的光化学-GaN半导体杂化材料

• 批准号: 267799003
• 负责人: Professor Dr. Ulrich Heiz
• 金额: --
• 依托单位: Walter Schottky Institut für physikalische Grundlagen der Halbleiterelektronik (WSI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/267799003?language=en
• 关键词: Photochemistry; metal; cluster; GaN; semiconductor

The use of light as energy source for driving chemical reactions has long been envisioned for various applications. Fostered by the possibility of using sun power for obtaining green-energy fuels, photocatalytic processes currently receive particular attention in both, fundamental and applied research. The most promising systems in heterogeneous photocatalysis are hybrid systems comprising a semiconductor with a co-catalyst. It is generally believed that illumination with photon energies above the semiconductor band gap generates electrons and holes which are separated due to a bending of the electronic bands at the semiconductor surface. As a result, electrons or holes travel to the co-catalyst where they enable catalytic reactions. The vast majority of studies has been dedicated to the search of new materials with improved photocatalytic activity. Although highly desirable for the rational design of more efficient catalysts, studies on more fundamental aspects are scarce. Their investigation is subject of the present project. Hybrid III-nitride semiconductors decorated with size-selected Pt-clusters in the size range of up to about 100 atoms will be used as a model system for investigating photocatalytic processes. In contrast to other photocatalytic materials such as TiO2 or ZnO, GaN allows for the tuning of its electronic properties by band gap engineering via alloying as well as both n- and p-type doping. For the photocatalytic reactions we focus on hydrogenation reactions. The photocatalytic efficiency of hybrid systems is influenced by (i) the interaction of the clusters with the reactants, (ii) the cluster-substrate interaction, and (iii) the dynamics of photogenerated charge carriers. While the first two are already essential for the reaction rate in the dark, the charge carrier dynamics govern the quantum efficiency under illumination. Our strategy for the project is to disentangle the influence of all three effects. We will study the dependence of the thermal reaction on the cluster size, the influence of the support on reactivity, and photochemical reactivity of size-selected clusters, respectively. Here, semiconductor preparation and characterization will be applied to design new structures with tailored properties, e.g. customized n-p (p-n) diode structures to deterministically control charge separation. Moreover, exploratory studies will be performed on nanostructured supports decorated with size-selected Pt-clusters. The identification of key parameters controlling the reaction mechanisms, such as the size of the clusters, the electronic properties of the semiconductor, and the charge carrier dynamics, will enable a deeper understanding of the catalytic properties of metal cluster/semiconductor systems. This will ultimately allow the tailored design of novel catalysts based on such materials.

长期以来，在各种应用中，将光作为驱动化学反应的能源的使用一直被设想。由于使用太阳能量获得绿色能量燃料的可能性，当前的光催化过程在基本和应用研究中都引起了人们的特别关注。异质光催化中最有希望的系统是杂种系统，其中包括带有共催化剂的半导体。通常认为，半导体带隙上方具有光子能的照明会产生电子和孔，这些电子和孔由于半导体表面的电子带的弯曲而分离。结果，电子或孔传播到共同催化剂，在那里它们能够促进催化反应。绝大多数研究都致力于搜索具有改善光催化活性的新材料。尽管对于更有效的催化剂的合理设计非常理想，但对更基本方面的研究很少。他们的调查是本项目的主题。杂交III氮化物半导体装饰在大约100个原子的尺寸范围内装饰的杂种二氮，将用作研究光催化过程的模型系统。与其他光催化材料（例如Tio2或ZnO）相反，GAN允许通过合金以及N-和P型掺杂来通过带隙工程来调整其电子性能。对于光催化反应，我们专注于氢化反应。杂交系统的光催化效率受（i）簇与反应物的相互作用的影响，（ii）簇 - 基底相互作用，以及（iii）光生荷载载流子的动力学。虽然前两个对于在黑暗中的反应速率已经至关重要，但电荷载体动力学控制着照明下的量子效率。我们对该项目的策略是消除所有三个效果的影响。我们将分别研究热反应对簇大小的依赖性，支持对反应性的影响以及大小选择的簇的光化学反应性。在这里，半导体的制备和表征将应用于具有量身定制特性的新结构，例如定制的N-P（P-N）二极管结构，以确定性控制电荷分离。此外，将对用尺寸选择的PT-Clusters装饰的纳米结构支持进行探索性研究。控制反应机制的关键参数的鉴定，例如簇的大小，半导体的电子特性和电荷载体动力学，将使人们能够更深入地了解金属簇/半导体系统的催化特性。这最终将允许基于此类材料的新型催化剂的量身定制设计。