Theoretical and experimental study of charge transfer processes in photocatalysis on anatase-TiO2

我们对化学反应的基本理解是相当有限的，因为假设的反应途径大多缺乏直接的证实。例如，在一个示例中，通常不知道分子在接收光激发的载流子之后是被吸附还是被解吸。气固相之间的电荷转移也是非常重要的，然而，缺乏适当的理论和实验技术来研究它。这项建议旨在发展这种方法，并将其应用于具有实际意义的案例研究。理论通常采用周期性模型，由于人工重复电荷之间的相互作用，需要进行校正。在气体/固体界面处的电荷校正（其中电荷可以位于任一相中）仍然是一个挑战。到目前为止，解决方案要么是对电荷的位置做出假设，要么是不自洽的。在这里，我们建议开发一个通用的和自洽的校正方案，在不同的复杂程度，在带电的1D，2D和3D系统的超原胞计算，并将其实现到一个标准的电子结构包（VASP）。考虑到问题的复杂性，简单的收敛性测试是不够的。由于我们不知道任何理论方法，避免电荷校正的问题是不是在一个权衡的大小收敛问题，唯一可接受的测试是experiments.Reactions上隔离表面可以遵循原子分辨率使用原子力显微镜（AFM）。然而，将强度变化分配给表面物种的充电主要是推测性的，因为它不能直接观察到。我们将开发一种基于电荷敏感开尔文探针力显微镜（KPFM）的方法，结合原子尺度上的非接触式原子力显微镜，用于明确识别表面物种的电荷状态。TiO 2可能是已知的最好的光催化剂，但是在绝大多数情况下，使用金红石，而已知金红石型在光催化方面是上级的。因此，理论和实验工具，在这里开发的，将进行测试锐钛矿-TiO 2，这是根据我们的初步理论结果，显示不同形式的金红石的化学途径。在原子尺度表征后，原子尺度KPFM的表面，和必要的方法的发展，我们将集中在CO和NO转化为化合物没有健康和环境危害。在这些情况下，跨界面的电荷传输起着特别重要的作用。

Our basic understanding of photocatalysis is quite limited, because the assumed reaction pathways mostly lack direct confirmation. E.g., it is often not known, whether a molecule gets adsorbed or desorbed after receiving the photo-excited carrier. Charge transfer between the solid and the gas phase is of great importance also beyond photocatalysis, however, appropriate theoretical and experimental techniques to study it are lacking. This proposal aims to develop such methods and to apply them in case studies of practical significance. Theory often applies periodic models which require corrections because of the interaction between artificially repeated charges. Charge correction at a gas/solid interfaces, where the charge can be located in either phase, remain a challenge. Solutions so far are either making assumptions on the location of the charge, or are not self-consistent. We propose here to develop a general and self-consistent correction scheme, at various levels of complexity, for supercell calculations in charged 1D, 2D and 3D systems, and implement it into a standard electronic structure package (VASP). Considering the complexity of the problem, simple convergence tests are insufficient. Since we are not aware of any theoretical method where the avoidance of the charge correction problem is not in a trade-off for size-convergence problems, the only acceptable test is experiment.Reactions on isolating surfaces can be followed by atomic resolution using atomic force microscopy (AFM). The assignment of intensity changes to the charging of surface species is, however, mostly speculative, because it cannot be observed directly. We will develop a method based on the charge sensitive Kelvin-probe force microscopy (KPFM), in conjunction with non-contact atomic force microscopy on the atomic scale, for unambiguous identification of the charge state of surface species. TiO2 is probably the best know photocatalyst but, in the overwhelming majority of the cases, rutile was used, while the anatase form is known to be superior in photocatalysis. Therefore, the theoretical and experimental tools, developed here, will be tested on anatase-TiO2, which, according to our preliminary theoretical results, shows chemical pathways different form rutile. After an atomic scale characterization of the anatase surface by AFM, and the necessary method developments in atomic scale KPFM, we will concentrate on the transformation of CO and NO into compounds without health and environmental hazards. In these cases, charge transport across the interface plays a particularly important role.