该【利用原位APXPS与STM研究H 2在ZnO(1010)表面的活化 】是由【niuww】上传分享，文档一共【2】页，该文档可以免费在线阅读，需要了解更多关于【利用原位APXPS与STM研究H 2在ZnO(1010)表面的活化 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。利用原位APXPS与STM研究H_2在ZnO(1010)表面的活化 Introduction The activation of molecular hydrogen (H_2) is a key process in many industrial and environmental applications. In particular, heterogeneous catalysis plays an important role in the activation of H_2 for chemical transformations. Zinc oxide (ZnO) is a promising catalyst for such reactions, due to its unique electronic and structural properties. Understanding the surface chemistry of ZnO during the activation of H_2 is therefore of great interest from both a fundamental and applied perspective. In this study, we have used in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) and scanning tunneling microscopy (STM) to investigate the activation of H_2 on the ZnO(1010) surface. Experimental Methods ZnO(1010) single crystals were prepared by a standard chemical vapor deposition technique. APXPS measurements were performed using a high vacuum system equipped with an X-ray source and a hemispheric electron analyzer. The pressure in the chamber was maintained at 10^-7 torr during sample preparation and then raised to 10^-2 torr for the APXPS experiments. STM measurements were conducted using a commercial STM system with a base pressure of 10^-9 torr. The ZnO surface was cleaned by annealing at 450°C for 1 hour in UHV prior to the experiments. Results and Discussion The APXPS spectra revealed the presence of Zn, O, C and H components on the ZnO surface in the presence of H_2 gas. The binding energy of Zn 2p was found to be shifted towards lower values in the presence of H_2, indicating the formation of Zn-H bonds on the surface. Quantitative analysis of the spectra showed that the coverage of H on the surface increased with increasing H_2 pressure, reaching a maximum at torr. At higher pressures, the H coverage decreased due to the formation of water on the surface. STM images of the ZnO surface in the presence of H_2 showed the formation of surface H species in the form of isolated adatoms and clusters. The size and density of these species were found to increase with increasing H_2 pressure, consistent with the APXPS results. The clusters were found to preferentially form on O-terminated regions of the surface, suggesting a strong interaction between H and O atoms. To understand the mechanism of H activation on the ZnO surface, density functional theory (DFT) calculations were performed. The calculations showed that the preferential activation site for H on the surface was the bridge-bonded O atom. The activation energy for dissociative adsorption of H_2 on this site was found to be relatively low, while the barrier for the formation of H clusters was higher. Conclusion In conclusion, we have used in situ APXPS and STM to study the activation of H_2 on the ZnO(1010) surface. The results showed that H species formed on the surface in the form of isolated adatoms and clusters, with a preferential interaction with O-terminated regions. DFT calculations provided insight into the mechanism of H activation on the surface. These findings may have implications for the design and optimization of ZnO-based catalysts for H_2 activation.
