(3jv) Computational Catalyst Design for Sustainable Processes

As a researcher in the field of electrochemistry, computational catalysis, and computational materials, my work revolves around understanding fundamental processes at the molecular level with potential applications in Sustainable and Green Chemistry. Computational catalysts design for storing energy in chemical bonds ­—the conversion of CO₂ into value-added chemicals (CO₂ER) and oxygen evolution reaction (OER) — was my focus the past research which can lay foundation for my future research at University of South Alabama.

My research revolves around the question “What happens on solid surface during a reaction?” which is an important question, especially for electrode reactions and catalysis. I started my research at Federal Urdu University Karachi by exploring electrode reactions using experimental electrochemistry tools (J. Electroanal. Chem. 2016, 775, 157-162 and Electrochem 2024, 5 (1), 57-69). After completing my Masters degree, I arrived in the US to start my Ph.D. studies, following the same vision and scientific question, I worked in computational electrolysis at Southern Illinois University Carbondale.

Ph.D. work: For a fundamental understanding of catalysis, I started my research on homogeneous catalysts and extended it to heterogeneous catalysts. My first research during my Ph.D. is the electrochemical reduction of CO₂ (CO₂ER) on homogeneous catalysts including d-metal complexes of cyclam and porphyrin. In the cyclam-based study, we identified some efficient and selective cyclam-based molecular catalysts for the electrochemical reduction of CO₂ to HCOO^- and CO. The effect of changing the metal centers in cyclam on product selectivity (either HCOO^- or CO), limiting potential, and competitive hydrogen evolution reaction (HER) was studied (Dalton Trans. 2021, 50(33), 11446-11457). In the case of porphyrin complexes, we explained the origin of selectivity for CO on cobalt porphyrin and the selectivity of HCOO^- on Ir- and Rh-porphyrin. Additionally, we identified the descriptors for product selectivity among CO, HCOO^- and HER and the optimal pH range for selective CO₂ reduction (Molecules 2023, 28(1), 375-386).

Next, I switched my focus to the heterogenous catalysis on metal/metal-oxide interfaces ((MO)₄/Cu(100), M = Fe, Co and Ni) for electrochemical reduction of CO₂ to C₁ products using computational hydrogen electrode model (CHE). This study demonstrates that tuning of (MO)₄/Cu(100) and using appropriate solvent provides an opportunity to regulate product selectivity and limiting potential for CO₂ER (Catalysis Today 2023, 409, 53-62). The objective of computational studies, sometimes, also requires the validation of computed limiting potentials and selectivity with improved models. Therefore, I conducted CO₂ER and OER on the same model catalysts as the previous one using the Constant Electrode Potential (CEP model). The CEP model is an improved computational model that intrinsically accommodates the field effect generated by applied potential. This study demonstrated that the CEP model is better for multi-step proton-electron transfer steps, but still, CHE works well for simple reactions like OER (J. Phys. Chem. C 2023, 127(48), 23170-23179).

Computational tools are very important to explain reaction mechanisms—which are otherwise difficult to observe—in catalysis or validate materials models in material chemistry. In my first collaborative projects with Dr. Shaowei Chen from the University of California Santa Cruze, I explained the origin of high reactivity and low overpotential for OER on Cl-rich NiFe₂O₄ spinel (Ni(OH)Fe₂O₄(Cl)). In that research, I identified Ni(OH)Fe₂O₄(Cl) as an active ensemble for OER due to close agreement between calculated (90 mV) and experimental overpotential values (200 mV) (Research, 2022, 2022, 13 pages). In my second collaborative project with the same group, I validated the structural and photoluminescent properties of organically capped CuOH nanostructures. (Adv. Mater. 2023, 35, 2208665).

Postdoc work: After my Ph.D. I joined the research group of Dr. Bin Wang at The School of Sustainable Chemical, Biological and Material Engineering, University of Oklahoma. Here, I worked on computational catalyst designs for the carboxylation of alkenes with CO₂ to produce unsaturated carboxylic acids on zeolite- and graphene-based catalysts. In my first project on zeolite-based catalysts, we aim to provide insights on CO₂-ethylene coupling on metal-exchanged MFI-zeolites and identify scandium (Sc) and yttrium (Y) dispersed in MFI zeolites as promising catalysts with low activation barriers. Additionally, we demonstrated that the electronegativity of metal atoms is the descriptor for the activation barriers for beta-hydrogen transfer, a rate-limiting step (ACS Sustainable Chem. Eng. 2024, 12(18), 6960–6968, also featured on Journal Cover page). To break this linear relationship, in a new study, we designed an active site, M-O-M (M = transition metal) in MFI zeolite to steer reaction mechanism which does not require beta-hydrogen transfer. This study shows that tuning M-O-M active site regulates the reactivity of CO₂-ethylene coupling and Zn-O-Zn is a better catalyst (manuscript drafted).Moreover, to prove the scalability of our study, we demonstrated that carboxylation of long-chain alkenes using CO₂ is sensitive to the structure of alkene (submitted in Catalysis Today). On the other side on graphene-based projects, we demonstrated that co-adsorbed water could work as a proton shuttle and lower the energy barrier for beta-hydrogen transfer in the direct coupling of CO₂ and C₂H₄ over atomically dispersed metal at graphene Edges (Chem. Eng. Journal. 2024, 488, 150922). In the next study, we used a bimetallic dimer (N₃M-MN₃) on defective graphene for CO₂-ethylene coupling which identifies Ir, Ni, Pd, Rh and Cu dimers as efficient catalysts (writing manuscript).

In addition to the above work, I enjoy working on different collaborative projects with collogues across academia and industry. So far, I have been involved in collaborative work with Philips 66 Catalysis Center, Oklahoma School of Science and Mathematics, The Department of Chemistry University of Oklahoma, and the Department of Microstructure Physics & Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Germany.