Surface Science in the Research and Development of Hydrate-Based Sustainable Technologies

Abstract

Compact gas inclusion in hydrates presents not only fascinating science but also wide-ranging applications in sustainable energy and environmental technologies. The surface of hydrates dictates many essential phenomena underlying hydrate-based processes such as hydrate nucleation and growth, mass transfer, heat transfer, agglomeration, adhesion, and adsorption. Thus, surface science falls within the core of hydrate science and engineering. This paper covers an insight perspective on surface science related to the research and development of hydrate-based sustainable technologies. We present insightful molecular views of hydrate surfaces with a focus on the interfacial premelting, and discuss how new fundamental advances benefit the sustainable engineering in the areas of greener and chemical-free flow assurance, energyefficient gas storage, carbon capture and storage, and recovery of methane (low-carbon energy) from natural hydrates. We highlight the prospects and challenges as well as stimulate future studies on this important topic.

“Nanoreactors” for Boosting Gas Hydrate Formation toward Energy Storage Applications

“…Certainly, any hydrate in a micropore must occur into a subunit-cell state, which raises a fundamental question concerning whether the hydrate structure could be confined to a subunit-cell scale. Moreover, theoretical predictions , and experiments have shown that hydrate structures are thermodynamically destabilized under high confinements, which means that gas hydrate formation in highly confined spaces (i.e., micropores) experiences thermodynamic inhibition effects similar to those in saline solutions. These factors must be taken into consideration for elucidating confined gas hydrates.…”

“…Strong solid–water binding pulls interfacial water molecules toward the solid surface, inducing a collapse of the interfacial water network into a distorted and high-density configuration equivalent to a compression effect . This density fluctuation of water decays rapidly along the surface normal and vanishes at a distance of around 1 nm from the solid surface, even though the collapse of the water network could extend to a distance of many nanometers from the solid surface. , This structurally mismatched layer is also known as the interfacial premelting layer. , Therefore, strongly hydrophilic (or charged) solid surfaces induce a distortion of the interfacial water structure that cannot be a seeding structure for the nucleation of gas hydrates. Consistent with this conclusion, computer simulations have shown that no gas hydrate cages could exist in the premelting layer next to highly hydrophilic (or charged) solid surfaces. , On the other hand, highly hydrophobic solid surfaces interact weakly with interfacial water through van der Waals (vdW) forces.…”

“…73,74 This structurally mismatched layer is also known as the interfacial premelting layer. 7,75 Therefore, strongly hydrophilic (or charged) solid surfaces induce a distortion of the interfacial water structure that cannot be a seeding structure for the nucleation of gas hydrates. Consistent with this conclusion, computer simulations have shown that no gas hydrate cages could exist in the premelting layer next to highly hydrophilic (or charged) solid surfaces.…”

“…The controllable liberation of gas from dissociating hydrates minimizes the risks associated with physical and chemical explosions. Therefore, large volumes of fuel gas stored securely in gas hydrates offer an opportunity for developing innovative technologies of gas storage. − This hydrate-based gas storage (HBGS) has the potential for applications in hydrogen economy ,, where hydrogen produced from renewable energies can be converted into hydrogen hydrates as a compact means of storage (Figure ). The hydrates are then dissociated to recover the hydrogen for consumptions.…”

“…The production of hydrogen using renewable energy is not described here. Reproduced with permission from ref . Copyright, 2022, American Chemical Society.…”