Layered transition metal hydroxides have been extensively researched for applications such as electrodes and electrocatalysts owing to their tunable redox properties based on various cation compositions. To control critical physical properties such as chemical adsorption and conductivity in these applications, topochemical control of anion compositions will be effective. While many reports have demonstrated the synthesis of nitrides and sulfides by reacting layered metal hydroxides with different anion sources, the existing methods often result in the formation of microcrystalline aggregates.1 Even under mild conditions, core-shell structures are formed through dissolution and reprecipitation.2 Hence, it is necessary to develop a new approach that allows direct reaction of anionic species with metal species in the crystal framework. In this study, we propose a reaction using bis(trimethylsilyl) sulfide ((Me3Si)2S), commonly used for preparation of metal sulfide nanoparticles,3 as a sulfur source for the direct sulfidation of layered metal hydroxides.Layered nickel hydroxide nanocrystals (Ni(OH)2nc) were reacted in a liquid phase with a desired amount of (Me3Si)2S. The product is denoted as S_Ni(OH)2nc. X-ray diffraction (XRD) patterns of S_Ni(OH)2nc shows that all peaks corresponded to β-Ni(OH)2, and no new peaks appeared. The original Ni(OH)2nc was an aggregate of hexagonal plate-shaped nanocrystals with sizes of 80 to 200 nm and thicknesses of 15 to 25 nm, and no significant changes in crystal morphology after the reaction were observed after the reaction. In contrast to the blue-green color of Ni(OH)2nc, S_Ni(OH)2nc was obtained as a blue-gray powder. X-ray photoelectron spectroscopy (XPS) spectra of S_Ni(OH)2nc revealed new photoelectron peaks attributed to S2p, which were within the range of sulfide compounds. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDS) mapping detected sulfur species at locations corresponding to plate-like crystals. Furthermore, quantitative analysis by EDS estimated the atomic ratio of sulfur to nickel in S_Ni(OH)2nc to be 5.0%, which corresponded well to the proportion of anion sites on the outer surface of Ni(OH)2nc. These results suggest that (Me3Si)2S reacts with Ni on the outer crystal surface of Ni(OH)2nc to form nickel sulfide compounds. Thus, sulfidation of layered metal hydroxides by (Me3Si)2S is effective in controlling the anion composition on crystal surfaces.(1) Y. Guo, T. Park, J.W. Yi, J. Henzie, J. Kim, Z. Wang, B. Jiang, Y. Bando, Y. Sugahara, J. Tang, and Y. Yamauchi, Adv. Mater., 2019, 31, 1807134. (2) B. Wang, C. Tang, H.-F. Wang, X. Chen, R. Cao, Q. Zhang, Adv. Mater., 2019, 31, 1805658. (3) R. García-Rodríguez, M. P. Hendricks, B. M. Cossairt, H. Liu, and J. S. Owen, Chem. Mater., 2013, 25,1233.
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