Electrochemical thinning of MoS2 on graphite substrate: A simple and scalable approach to monolayer production

Electrochemical thinning of MoS2 on graphite substrate: A simple and scalable approach to monolayer production

• Autor
• Renan G. de Assis
• Co-autores
• Rogério de A. O. Storai , Matheus F. F. das Neves , Murilo Santhiago
• Resumo

• Molybdenum disulfide (MoS2) is a two-dimensional material widely investigated as an electrocatalyst for the hydrogen evolution reaction (HER). Many bottom-up and top-down synthesis techniques are used to prepare monolayers. Electrochemical routes using metallic electrodes stand out for their ability to produce high-aspect-ratio MoS2 monolayers.[1] However, the preparation of such electrodes is laborious, costly, and may lead to contamination by metallic residues. Alternatively, carbon-based electrodes, such as highly oriented pyrolytic graphite (HOPG), offer a lower cost, simpler preparation, high chemical stability, good conductivity, and a more favorable substrate-MoS2 coupling. In this context, we propose using HOPG as an electrode to produce high-aspect-ratio MoS2 monolayers for electrochemical applications. By combining mechanical and electrochemical thinning in a three-electrode cell, we obtained multiple thinned flakes with lateral dimensions of approximately 100-150 um. Raman and photoluminescence spectroscopy revealed, respectively, a separation between the E12g and A1g vibrational modes of approximately 20 cm-1 and a strong emission, indicating the monolayer nature of the exfoliated regions.[2] High-resolution Mo and S spectra obtained by X-ray photoelectron spectroscopy (XPS) indicated a low oxidation level (approximately 8 %) of MoS2 after the electrochemical thinning step. In addition, morphological analyses by scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed the high coverage and uniformity of the electrochemically thinned areas. Finally, Raman and XPS analyses indicated, respectively, the absence of defects in the graphite basal plane and low electrochemical oxidation of the substrate (with an increase of approximately 5 % in carboxylate groups). Therefore, HOPG proves to be a stable and efficient platform to produce high-aspect-ratio MoS2 monolayers, opening new pathways for the preparation of two-dimensional materials.

  References

  [1] FREITAS, N. DE et al. Nanoscale, v. 14, n. 18, p. 6811–6821, 1 jan. 2022.

  [2] FLORINDO, B. R. et al. Journal of Materials Chemistry A, v. 11, n. 37, p. 19890–19899, 1 jan. 2023.

• Palavras-chave
• HOPG, electrochemical thinning, single layer MoS2
• Modalidade
• Pôster
• Área Temática
• Materiais Avançados