NSRRC Activity Report 2022

Physics and Materials Science 019 absorption (XAS) at TLS 09A2 . These findings indicate that a model based on the diffusion length of H on graphene and the size effect of Ti SACs should be developed. Figure 2(a) presents the hydrogen spillover and diffusion ability of the H atoms near each SAC and single-cluster catalyst. Figure 2(b) shows the simulated relationship between the number of atoms in the Ti SAC and the hydrogen storage efficiency. The result suggests that SACs have the highest hydrogen storage capacity. Figure 2(c) depicts the perfect condition for 100% hydrogen storage: a TiH 6 SAC structure on graphene. In summary, Wu and Chen designed and simulated hydrogen spillover from single-atom to single-cluster catalysts by precisely controlling the coverage of Ti on graphene. The atomic nature of C−H bonds on graphene and the optimal H storage capacity were spectrally characterized using ARPES, XPS, and XAS. Given the short migration distance of H atoms diffusing on graphene at room temperature, the simulation results provide a general rule that will enable rational design of carbon-supported physisorbed metal catalysts for chemisorbed H storage through spillover. (Reported by Sheng-Shong Wong, National Cheng Kung University) This report features the work of Chung-Lin Wu, Chia-Hao Chen and their collaborators published in ACS Energy Lett. 7 , 2297 (2022). TLS 08A1 XPS, UPS TLS 09A2 Spectroscopy TLS 24A1 XPS, UPS, XAS, APXPS • XPS, NEXAFS, UPS • Materials Science, Chemistry, Surface, Interface and Thin-film Chemistry, Condensed-matter Physics, Chemical Materials References 1. J.-X. Liang, J. Lin, X.-F. Yang, A.-Q. Wang, B.-T. Qiao, J. Liu, T. Zhang, J. Li, J. Phys. Chem. C 118 , 21945 (2014). 2. G. Srinivas, Y. Zhu, R. Piner, N. Skipper, M. Ellerby, R. Ruoff, Carbon 48 , 630 (2010). 3. J. W. Chen, H. C. Huang, D. Convertino, C. Coletti, L. Y. Chang, H. W. Shiu, C. M. Cheng, M. F. Lin, S. Heun, F. S. S. Chien, Y. C. Chen, C. H. Chen, C. L. Wu, Carbon 109 , 300 (2016). 4. T. Mashoff, M. Takamura, S. Tanabe, H. Hibino, F. Beltram, S. Heun, Appl. Phys. Lett., 103 , 013903 (2013). 5. J.-W. Chen, S.-H. Hsieh, S.-S. Wong, Y.-C. Chiu, H.-W. Shiu, C.-H. Wang, Y.-W. Yang, Y.-J. Hsu, D. Convertino, C. Colet- ti, S. Heun, C.-H. Chen, C.-L. Wu, ACS Energy Lett. 7 , 2297 (2022). 6. D. Lizzit, M. I. Trioni, L. Bignardi, P. Lacovig, S. Lizzit, R. Martinazzo, R. Larciprete, ACS Nano 13 , 1828 (2019). Spatially Resolved Patterned Doping in Monolayer Transition-Metal Dichalcogenides Area-selective doping of transition metals on the micron scale was achieved in tungsten-based dichalcogenides using a novel “open-replace-close” technique. I n recent years, monolayer transition-metal dichalcogenides (TMD) have attracted tremendous attention, owing to their potential for electronic, magnetic, optical, and catalytic applications. It has been recently recognized that substitutional doping of transition- metal atoms in monolayer TMDs is extremely useful for controlling their exotic physical and chemical properties, which can be improved for applications. 1−3 Substitutional doping of transition-metal atoms is an established method to tune material properties, which is typically carried out during the epitaxial growth of material films, 2 but it does not allow the spatial control of the doping material. 3 In a recent collaborative study reported in Nanoscale , researchers in Japan and Taiwan have developed a novel method to achieve area-selective doping on tungsten- based TMD monolayers. 4 In order to carry out spatial characterization of their micron-scale doping method, the authors used a combination of techniques, including optical spectroscopy, scanning-transmission electron microscopy (STEM), scanning photoelectron microscopy (SPEM), and micro-X-ray photoelectron spectroscopy (µ-XPS), and confirmed the efficacy of their “open-replace- close” (ORC) technique for the area-selective doping of monolayers. Figure 1 (left panel, see next page) shows a schematic diagram of the three phases of the ORC substitution process for WSe 2 doped with Cr. In Phase I, the desorption of Se under the assistance of hydrogen proceeds according to the chemical reaction WSe 2 (s) + H 2 (g) → WSe 2 -x(s) + H 2 Se(g),