Research
A. Computational electrochemistry
In electrochemistry one studies how electrical energy converts into chemical energy and vice versa. To model electrochemical half-cell reactions in a realistic fashion, one would need to simulate (1) electrode of interest at constant potential (2) explicit interactions between electrode and electrolyte (3) relevant ionic concentrations in the solvent. Recently, we developed a computational technique based on partially occupied wannier functions to compute dipole moment of water molecules near a metal surface within the framework of ab initio molecular dynamics. (manuscript under review) We are currently working on the implementation of a thermo-potentiostat in CP2K.
B. Battery materials
Li-ion batteries have revolutionized the battery industry. In recent years, scientists have been trying to develop solar batteries: batteries that can be charged by sunlight. In several solar batteries the cathode is composed of stacks two different materials with staggered band gap alignment (type-II semiconductor heterojunctions), mainly to spatially separate the photo-generated excitons. An example of such a photocathode material in the context of Li-ion batteries is MoS2/MoO3 combination. In this case, MoS2 faces the electrolyte solution and Li-ion mostly intercalates in MoS2. Light excitation is also performed selectively on MoS2 while MoO3 acts as the type-II partner During the discharge cycle of a Li-ion battery, Li-ions intercalate the cathode. For solar charging to happen it is important that the material retains its semiconductor property while Li-ions intercalate. It is well known in the literature that MoS2 undergoes a transition to a metallic phase upon Li-intercalation. In a recent theory/experiment collaborative study we should that the presence of a heterojunction partner can shift the phase transition point to a higher Li-ion concentration owing to the extraction of electron density. (manuscript under review)
C. Defects in materials
Defects play an important role in determining electronic and mechanical properties of several materials. We are currently working on defects related to graphene oxide (GO) and grain boundaries in Au. The most common way to characterize defect densities in GO is to count the total number of sp3 carbon atoms in the system. In a recent study we showed that this count increases linearly with the increase in the oxygen/carbon ratio. This trend is not the most desirable one since one would expect the surface to be significantly more distorted at high oxygen/carbon ratio. Hence, in principle, one would want a metric whose slope, as a function of oxygen/carbon ratio, would be different at low and high defect densities. In a recent study, we introduced such a metric. (Carbon Trends 2024, 14, 100323) Here, we computed the area of the defect polygons. It turns out that this metric follows the trend in the sp3 carbon atoms that are exclusive to the defect polygons at low defect densities but increases more rapidly at high oxygen/carbon ratio. We are also studying the role of Au grain boundaries in activating CO2.
D. Catalysis
Our group studies mechanisms of reactions in solution (molecular complexes), on surface (periodic systems) and in enzymes.