Inelastic Neutron Scattering of Methane Hydrate Confined in Hydrophilic and Hydrophobic Porous Model Carbons

Methane hydrate (MH), an abundant natural gas source, is an ice-like compound formed when water and methane molecules interact under specific pressure and temperature conditions. The confined environment and surface chemistry of geological sediments play an essential role in promoting or hindering the formation of MH crystals. In this work, we tracked the hydrogen atoms of confined water and confined MH in porous model carbon by inelastic neutron scattering (INS) experiments. Ordered mesoporous carbon (OMC) and hydrophilic ordered mesoporous carbon (HOMC) are employed as nanoreactors to induce MH formation at 20 bar and 200 K within 1 h. The INS spectra reveal the unique features of nonfreezable water in wet HOMC (10% pore filled), and confined MH is identified in both wet HOMC and OMC (60% pore filled) upon pressurization. Additionally, a contribution of nonreactive confined ice is observed in the latter case. The application of INS spectroscopy provides distinctive insights into the fundamental characteristics of water and methane hydrate confined in different environments at the molecular level.