Minkyoung Jung

The global rise in atmospheric CO₂ concentration and its societal impact urges the development of sustainable carbon management via carbon capture, utilization, and storage (CCUS) strategies. Although CCUS addresses a challenge of global scale, the key processes occur at nanoscale interfaces among CO₂, water, and solids, where reaction kinetics, thermodynamics, and transport determine CO₂ fate and process performance, influencing the overall efficiency and sustainability of CCUS. Therefore, a better understanding and precise control of nanoscale interfacial chemistry in CCUS processes are vital. This review introduces the fundamental principles of CO₂ interfacial reactions involved in CCUS, followed by a detailed examination of nanoscale interfacial processes in CO₂ capture, utilization, and mineralization. We also explore the properties of various interfaces, the mechanisms governing nanoscale CO₂ interactions, and their impacts on overall CCUS performance, highlighting how a deeper understanding and control of interfacial reactions can contribute to achieving net-zero CO₂ emissions (NZE) targets. To support the characterization of these dynamic and complex interfacial processes, we discuss advanced characterization techniques for studying interfacial phenomena in carbon management systems. Finally, we suggest future research directions and opportunities in advancing carbon management by bridging nanoscale insights to field-scale applications of CCUS.

Barium Titanate, BaTiO3 (BTO), is increasingly explored as a polarization-assisted photocatalyst for water treatment due to its reactive oxygen species (ROS)-generation capacity. Because these ROS interact strongly with redox-active metals, it is important to evaluate BTO’s influence on manganese (Mn) cycling, a major redox pathway in aqueous environments. Many engineered and natural waters where BTO may be applied contain high salinity and elevated sulfate concentrations. Therefore, this study investigated how high-salinity and sulfate-rich water chemistries alter BTO’s interfacial properties and, in turn, Mn redox chemistry. Under 0.5 M NaCl, BTO produced superoxide and hydroxyl radicals that drove substantial MnO2 formation. Interestingly, 28 mM sulfate increased Mn oxidation 1.4 times (65.7 ± 4.0 μM MnO2 formation with 4 g/L BTO, at 6 hr). Spectroscopic and dielectric analyses show that sulfate elevates oxygen-vacancy density and induces BaSO4-related surface restructuring, thereby enhancing BTO’s redox activity. Sulfate incorporation, rather than MnO2 deposition on BTO, was primarily responsible for increasing the dielectric constant and improving photocatalytic dye degradation. By demonstrating how sulfate-driven restructuring configures BTO’s defect chemistry and redox performance, this study establishes a critical link between water chemistry, perovskite photo-reactivity, and their influence on Mn cycling in complex aquatic environments.

Two-dimensional (2D) molybdenum disulfide (MoS₂) is a nanomaterial of emerging interest with distinctive properties that are useful in water treatment and photochemical applications. For example, redox pathways driven by MoS₂ nanosheets can facilely convert ferric ions to ferrous ions, improving Fenton and Fenton-like reactions. Here, we show how photo-Fenton/Fenton-like reactions influence the morphologies, chemical compositions, and photocatalytic activities of MoS₂ nanosheets in aqueous environments. Under light illumination, aqueous iron promoted MoS₂ nanosheet dissolution, increasing its thickness and creating circular pits on the basal surface. Furthermore, the fraction of oxidized Mo species in the MoS₂ nanosheets continuously increased over the reaction. These results suggest that MoS₂ is first oxidized, then nanopits form on its basal surface, and finally is penetrated as the pits are deepened and enlarged by dissolution. We also demonstrate that the photocatalytic activity of the MoS₂ nanosheets generates reactive oxygen species (ROS) and electron holes, both of which facilitate the formation of circular pits in MoS₂ nanosheets and their oxidation. Moreover, during a 1 h dissolution test, the MoS₂ nanosheets' surfaces were significantly oxidized, which decreased their photocatalytic activity by ∼37% through photo-Fenton reactions. These findings emphasize that exposure to aqueous iron and light alters the properties of MoS₂ nanosheets, changing their dissolution kinetics, pathways, and photocatalytic activity. These changes are all directly linked to their reliability in photochemical applications and their environmental fate.

Struvite (NH₄MgPO₄·6H₂O) mineralization is an effective technique for removing ammonium and phosphate species from wastewater. However, its wider use faces obstacles because of the copresence of various pollutants in wastewater and the additional requirement for magnesium to achieve proper supersaturation conditions. To address these challenges, this study developed novel mineral-hydrogel composites that can remove ammonium and phosphate simultaneously via heterogeneous struvite and calcium phosphate (CaP) mineralization in hydrogel matrices. The composites include in situ formed struvite and CaP mineral seeds, decreasing the nucleation energy barrier of struvite and CaP formation and promoting their heterogeneous nucleation kinetics even under undersaturation conditions in bulk solution. The dual struvite and CaP seeded composites can simultaneously reduce the ammonium and total phosphate concentrations up to 60% (26.3 mg of N/g) and 91% (9.54 mg of P/g), respectively. The average particle sizes in composites were increased from 6.12 to 14.8 nm after wastewater treatment. Moreover, various ions commonly existing in wastewater did not significantly interfere with the removal of ammonium and phosphate. Thus, these new mineral-hydrogel composites can provide an innovative way to lower nutrient levels before discharge to streams. Moreover, encapsulating ammonium and phosphate in mineral-hydrogel composites enables their upcycling in agricultural or biorefinery applications.