Adsorption-induced two-way nanoconvection enhances nucleation and growth kinetics of methane hydrates in confined porespace

Despite confined nanospace is known as corresponding to fast hydrate kinetics, hydrate nucleation and growth mechanisms behind the promotion effect have not been thoroughly understood. Here we estimated hydrate nucleation and growth kinetics in confined porespace and proposed a new adsorption-induced two-way nanoconvection mechanism, which may constitute the essence of the confinement effect. Hydrate formation kinetics loaded by activated carbon (AC) suggest a discrete two-stage adsorption that attributes to methane physical adsorption and hydrate formation, respectively, and the promotion of methane physical adsorption on hydrate nucleation in inner pores was first presented. Impressively, the two-way convection at molecular scale gives rise to hydrate fibers, which grow out from inner pores and significantly depend on the contents of pre-adsorbed water, and this finding inversely confirms the nanoconvection mechanism. This work provides a novel perspective on improving the understanding of hydrate nucleation and growth kinetics in confined porespace and sheds light on the application of AC-based methane storage.