Polymer Waste Upcycling
Polymers are ubiquitous materials produced at a large scale. The non-degradable polymer waste with low recycling rate poses severe environmental threats. We investigate catalytic reactions converting polymer back into the monomers or other petroleum-based chemicals, to achieve a circular economy. We specifically tackle challenges rising from the unique properties of the polymer feedstocks. Two sub-themes are: 1) tailoring the bifunctionality of transition-metal-carbide surfaces for impurity-compatiable hydrocracking; 2) understanding polymer behaviors to decipher and facilitate upcycling kinteics.
Rigorous Structure-Function Relationship
Many catalytic reactions occur on the surface of metal nanoparticles. The size, shape, and density of the nanoparticles determine their reactivity. However, these structural parameters often change simultaneously in catalyst synthesis, and thus their catalytic effects (“structure-function relationship”) are difficult to cleanly elucidate.
Inspired by the epitaxial growth theory of self-assembled quantum dots, we developed a framework to tune each structural parameter independently. The correlation between particle density and size is broken with the strain-limited growth of epitaxial islands. Through collaboration, we use in-situ spectroscopy (X-ray absorption spectroscopy, XAS, probe-IR, low-energy ion scattering, LEIS) and scanning transmission electron miscroscopy (STEM) to model the structure of the metal particles. The platform is deployed to study reactions involving inter-particle phenomenon, establishing rigorously structure-function relationships as the foundation for rational catalyst design.
Kinetically Restrained Ostwald Ripening
Low-nuclearity metal clusters (Mn) are desired in catalysis due to the unique electronic properties and structural adaptability. However, the high surface energy of Mn leads to strong sintering tendency at high temperature. We use kinetically restrained Ostwald Ripening to create versatile metastable Mn for high-temperature catalysis. The discrepancy between the adhesion energy of metal adatoms on the anchoring and barrier oxides create interfacial kinetic barriers, restraining Ostwald Ripening to within the anchors. The nuclearity of Mn and surface property of the anchor provide levers for catalytic functionality. This strategy will be applied to the mechanism-informed catalyst design for H2 storage/release and CO2 utilization.
Renewable Carbon-Neutral Chemical
Currently, the chemical industry heavily relies on petroleum-based carbon feedstocks, representing an unsustainable model with significant carbon footprint. We are developing new processes and catalysts that integrate bio-resources (e.g., lignin) and CO2 into existing chemical manufacturing routes as renewable feedstocks, enabling the production of carbon-neutral/negative platform chemicals (e.g., styrene and ethanol). We aim at establishing new conversion routes, designing novel catalysts, and analyzing process footprints.
