(6bf) Fundamental Design of Sustainable Catalytic Reactions at the Water-Energy-Food Nexus

Many of the grand challenges facing society are linked by energy and resource tradeoffs. Production of fertilizers and clean water consumes vast amounts of energy. Synthesis of fuels and chemicals depends on fossil-derived compounds and clean water sources, yet reliance on fossil resources to meet energy needs generates deleterious atmospheric emissions. Combined technological approaches can be used to overcome classical challenges for problems that are at the intersection of multiple fields. Engineering the sustainable synthesis of chemicals and fuels via reactions facilitated by catalyst surfaces comprises a key vehicle for approaching these problems. Fundamental mechanistic insights are required to drive rational catalyst design and materials discovery.

Renewable reagents may be converted to energy-dense fluids in order to serve as the bridge between cheap, intermittent renewable energy sources and reliable, transportable energy delivery. For instance, CO₂ may be selectively converted to useful products using tailored catalysts. In situ surface characterization enables development of non-precious metal catalysts for efficient conversion of CO₂ to CO, a chemical building block for methanol and other chemicals. During my PhD work under Prof. Jingguang Chen, Ni/CeO₂ catalysts were found to exhibit extensive oxygen exchange between the CeO₂ support and CO₂. Effects of Ni particle size and oxidation state on reaction selectivity were determined, and non-precious NiFe bimetallic catalysts were developed in order to tune reaction selectivity to CO at high activity. In order to eliminate reliance upon fossil-derived H₂ for methanol synthesis, a one-step process to convert an underutilized natural gas co-product with CO₂ to methanol was sought. Since no thermal route is thermodynamically allowable, non-equilibrium plasma activation was employed to achieve direct alcohols synthesis. As an NSF fellow, I was able to design and build an in situ FTIR plasma-catalysis reactor in order to combine observation of surface intermediates with kinetic and isotope experiments. Coupled with kinetic modeling, the results revealed the role of the catalyst surface and the reaction mechanism. Similar techniques were employed to overcome classical limitations to ammonia synthesis. Ammonia – the major component in fertilizer and a carbon-free alternative fuel – faces century-old challenges to efficient and sustainable synthesis due to thermodynamic constraints, catalyst scaling relations, and dependence upon fossil-derived H₂. As I will discuss in my oral presentation at this year’s meeting, in situ characterization provided the first direct observation of surface reactions in the presence of plasma activation for ammonia synthesis as well as evidence of reaction intermediates not observed in the thermal catalytic process.

Future plans for my independent research group will use hybrid technologies to innovate sustainable chemical synthesis processes, while pursuing fundamental understanding of mechanisms and surfaces in order to guide materials discovery. Projects may couple catalytic surfaces with thermal, electrochemical, and plasma activation, in addition to linking with membrane separation processes for water purification and possible interfacing with biological approaches. Studies will employ in situ X-ray and infrared characterizations as well as isotopic and kinetic experiments in order to gain mechanistic and materials insights. These insights can enable development of descriptors for advancing and guiding research, especially in conjunction with computational modeling. I seek an interdisciplinary environment that encourages collaboration across areas of expertise.

Teaching Interests:

I am especially interested in teaching courses in kinetics, thermodynamics, and introductory chemical engineering mass and energy balances. I would be excited to develop a course on surface reactions and kinetics with applications to experimental surface characterization techniques. I would also like to develop a course on engineering sustainability at the water-energy-food nexus, with an emphasis on large-scale energy and mass balances, approaches to engineering problem-solving, and exposure to frontiers in water-energy-food research.

My teaching experience includes training undergraduates, PhD students, and visiting scholars and professors in the laboratory; serving as a teaching assistant; and mentoring more than 30 recently immigrated students on independent research projects at a resource-strapped high school through a program I established and for which I successfully secured funding and organized a poster presentation event at Columbia University.

My goal is to guide students toward having a stake in their learning, which facilitates internalization of content and critical thinking. I employ independent projects that drive students to ask their own questions, group work to encourage engagement in shared efforts, and active learning through in-class problem solving and use of the Socratic method of teaching by systematic questioning. Given the importance of communication in scientific advancement, I also incorporate exercises to develop students’ written and oral communication skills.