October 1, 2025

Xinyu Yao, a Ph.D. candidate in the Energy Resources and Petroleum Engineering program at King Abdullah University of Science and Technology (KAUST), has successfully defended her Ph.D. dissertation titled “Molecular insights into bulk and interfacial properties of brine systems with gas.”

Her research, conducted under the supervision of Professor Bicheng Yan, provides molecular-level understanding of the bulk and interfacial behaviors of gas–brine systems that are essential to carbon capture and storage (CCS) and subsurface hydrogen storage. The defense committee, chaired by Professor Yoji Kobayashi, included Professor Bicheng Yan as advisor, Professor Hadi Nasrabadi as external examiner, and Professors Hussein Hoteit and Shuyu Sun as committee members.

In her dissertation, Xinyu employed molecular dynamics simulations to explore how gas composition and interfacial structure influence key thermodynamic and transport properties in systems relevant to CCS and hydrogen storage. Her findings offer important insights for improving the efficiency, safety, and sustainability of geological CO₂ sequestration and hydrogen energy storage processes.

Ph.D. Thesis Abstract:

Carbon capture and storage (CCS) is considered to be a crucial strategy for controlling CO2 emissions and combating climate change. Concurrently, Hydrogen has emerged as a promising clean and renewable energy resource to replace fossil fuels and facilitate the transition to a decarbonized society. In both technologies, fundamental understandings of the interfacial properties of the involved system is essential. Due to the difficulty associated with purification processes, the presence of impurities such as nitrogen can significantly influence the efficiency and safety of CO2 storage. In particular, capillary pressure plays a key role in determining CO2 migration, trapping, and storage security in deep saline aquifers and hydrocarbon reservoirs. Therefore, elucidating the effects of such impurities on capillarity is vital for accurate prediction and process optimization. In the context of hydrogen energy, cushion gases are commonly used to facilitate the withdrawal of hydrogen stored in saline aquifers and depleted oil and gas reservoirs. The bulk and interfacial properties of hydrogen–brine and cushion gas–brine systems critically affect the efficiency, economics, and environmental performance of subsurface hydrogen storage. In this dissertation, Molecular dynamics simulations are conducted to investigate interfacial properties in systems relevant to carbon capture and storage (CCS) and hydrogen storage, including N2–oil–water mixtures, hydrogen–brine systems, and CO2–brine–silica systems. The findings offer insights that support the design and optimization of efficient and environmentally sustainable CCS and hydrogen storage processes.