Group Research

Ammonia (NH₃) is one of the most essential agricultural compounds being used as the primary source of nitrogen in fertilizers. The Haber-Bosch process is a time-tested synthetic method for NH₃ in large quantities from N₂ and H₂. While the reaction of N₂ and H₂ gas is thermodynamically allowed at room temperature and pressure, the initial dissociation of both reactants required to facilitate their combination is highly unfavorable, both thermodynamically and kinetically. Although a transition metal catalyst, such as Fe, may lower the barrier for the dissociation of N₂, high temperature is still required to hasten this process, which consequently demands high pressure to remain nearly spontaneous. Through first-principles methods, I investigate alternative metal catalysts that could not only lower dissociation barrier for N₂ but also harness the energy of light, via plasmon resonance, to facilitate this process. With light instead of heat as an additional driving force, a high-dissociation rate at lower temperatures may be achieved, which would then relax the need for higher pressures and thus improve the energy efficiency of the process overall.

The capture of CO₂ from the earth’s atmosphere is a key strategy for the mitigation of global warming. However, conventional negative emissions technologies, such as the injection of CO₂ into geological formations, require separate steps for the removal of CO₂ from the air and its storage, resulting in significant energetic and logistical hurdles. The sequestration of CO₂ from sea water, which contains CO₂ at 150 times its concentration in air, provides a promising alternative to such methods. Here, one particularly promising proposal is the sCS² approach where CO₂ is mineralized into carbonate using an electrolytic reactor, enabling a one-step carbon capture and storage process that may be powered by renewable energy.  Yet, knowledge of the fundamental, molecular processes involved in such an approach is limited. We aim to perform multi-level simulations, harnessing both ab-initio correlated electronic structure theory, as well as molecular dynamics calculations to elucidate the mineralization pathways of carbonates with Mg²⁺ and Ca²⁺ cations in order to assess their viability in CO₂ sequestration. Insights from these studies will provide valuable understanding for the design of large-scale mineralization facilities.

The RPA has attracted rising interest in the recent years as a method on the fifth rung of the Jacob’s ladder. The higher accuracy of the RPA compared to commonly used semi-local density functionals is however accompanied with significantly higher costs, with RPA calculations often exceeding current computational capacity. Using the embedded correlated wavefunction (ECW) theory, we want to accelerate the costly RPA calculations with either a cluster embedding approach or a periodic embedding approach. We also are working on combining the ECW theory with implicit solvation and the grand canonical treatment of electrons, which has been shown to be possible for RPA calculations, to model solvation and electrochemical potential effects.

During my PhD, I was trained in using density functional theory and wave function theory methods to understand the interplay of hydrogen bonds and transition metal complexes in C–H activation, both by enzymes and molecular catalysts. As a member of the Carter research group, I will lead an effort to identify the optimal facets of Cu electrocatalysts for ammonia (NH₃) synthesis by reduction of nitrate (NO₃^–). While Cu electrocatalysts are promising for nitrate reduction to ammonia, the reaction pathway could result in several byproducts which are both pH dependent and electrocatalyst facet-dependent. The standard simulation technique, density functional theory, does not provide the accuracy required to assess electrochemical kinetics. Therefore, I will apply embedded correlated wavefunction theory, a quantum mechanical simulation method developed by Prof. Carter, to simulate nitrate reduction reaction on a variety of Cu facets that could provide a carbon-emission free route to ammonia production.