Comparative Raman Investigation of Hydrogen and Water Intercalation in Graphite under High Pressure

The high-pressure intercalation behavior of graphite with hydrogen and water was investigated using in situ Raman spectroscopy up to 10 GPa. Raman spectra were collected under compression to monitor structural and electronic modifications. Evidence of hydrogen intercalation into graphite was observed near 5.5 GPa, indicated by the appearance of distinct blue-shifted and split hydrogen vibron peaks. This pressure corresponds to the solidification of hydrogen, which significantly reduces its kinetic diameter and facilitates diffusion into the interlayer pores of graphite. In contrast, the graphite–water system exhibited no such anomalies. Comparative analysis of the G and 2D Raman bands between the two systems highlights the potential influence of molecular size, polarity, and chemical inertness on intercalation accessibility under high-pressure conditions.