(7id) Materials and Methods for Sustainable CO2 Conversion Towards Hydrocarbon Generation

The current energy and environmental scenario demands immediate attention towards mitigating atmospheric CO₂ and repurposing it for hydrocarbon generation. Carbon capture and sequestration (CCS) routes for CO₂ reduction attracted sufficient investment over the last few years. However, its scale of operation (about 35 Mtpa, in early 2017) is far below the CO₂ emissions (about 35 Gtpa, in 2015). Probing other methods for sustainable conversion of CO₂ is thus a prime necessity. Amongst the different routes of CO₂ conversion, solar energy based options like solar photocatalytic or solar thermochemical cycles (STC) garnered a lot of interest. Photocatalysis can be a low temperature process, however the current materials are mostly limited to using UV light for the purpose and the rates of CO₂ conversion are still very low. STC can achieve superior rates of CO₂ conversion, but at the cost of high temperatures of operation (more than 1000 °C). Reverse water gas shift – chemical looping (RWGS-CL) presents the benefits of these processes without facing their limitations. It can operate at low temperatures of about 500 °C with even better CO₂ conversion rates.

Mixed metal oxides are key elements in RWGS-CL process. Perovskite oxides (ABO₃) in particular have shown promising results for this purpose. RWGS-CL operates in two-steps: the first one being generation of oxygen vacant materials (ABO_3-δ) by heating in presence of hydrogen. In the second step, these oxygen deficient materials regain their stoichiometric forms (ABO₃) while CO₂ is converted to CO. Oxygen vacancy formation is the key step that governs RWGS-CL process. Hence, DFT-calculated oxygen vacancy formation energy (E_vac) serves as an appropriate descriptor for this process. Since perovskite oxides are perfect platforms for material composition tuning, we screened several perovskite oxides based on our descriptor (E_vac). The predicted materials were subsequently synthesized via Pechini method and tested for CO₂ conversion performance. We could demonstrate highest CO_­2 conversion at lowest temperatures (~450‑500 °C). The role of intrinsic material parameters towards CO₂ conversion has been studied as well.

On the photocatalytic frontiers, the use of materials with capability of harvesting solar light is encouraging. Oxy-nitrides, transition metal dichalcogenides and perovskite oxides are some potential candidates for this purpose. We hereby computationally investigate the role of heterojunctions, strain and vacancy defects for tuning the band gap and band edges of these materials. Investigating all these material properties provides the backbone for material prediction and unravelling the catalysis mechanism for a vast range of chemical reactions

Teaching Interests:

Basic chemical engineering principles are not restricted to any particular discipline. They can be applied to a lot of common natural phenomena happening around us. These basic principles are key to any materials and methods development and discovery. Over the years, I had the experience of being Teaching Assistant in several courses (Chemical Engineering Thermodynamics, Transport Phenomena, Numerical Methods, and Process Dynamics and Control). Along with these, two other courses (Material and Energy Balance and Chemical Reaction Engineering) form the core of chemical engineering. I am interested in teaching any of these courses. During my graduate studies I also enjoyed the role of mentoring undergraduate students. In future, I would like to advise and mentor students in their various academic endeavors.