Thesis Defense: Ruiqi Yang

Please join Yale Chemistry for a thesis seminar with Ruiqi (Rachel) Yang, Pfefferle Group.

Title: Strain Engineering in Confined Graphene Oxide Systems: Implications for Catalysis and Superconductivity

Summary: Nanoscale confinement offers a powerful strategy for controlling material behavior by restricting geometry, modifying local bonding environments, and generating strain that is difficult to access in bulk systems. This thesis investigates graphene-based confinement architectures as tunable platforms for strain-mediated catalysis and high-pressure materials stabilization. Two major systems are examined: sulfur-linked graphene oxide nanosheets and graphene oxide nanoscrolls. Through structural characterization, Raman spectroscopy, high-pressure studies, and catalytic testing, this work demonstrates that confinement geometry and nanoparticle identity can strongly influence the strain state of graphene oxide hosts. In catalytic CO2 hydrogenation, these strain differences correlate with distinct product pathways, with NiO confined in graphene oxide nanoscrolls favoring ethylene formation and NiO confined in sulfu-linked graphene oxide favoring ethane formation. In high-pressure studies, graphene oxide confinement further enables the formation and partial retention of metastable sulfur-containing phases and nanoparticle composites after decompression. Together, these findings establish strain-in-confinement as a useful design principle for tuning reaction selectivity and stabilizing functional materials. Future directions include comparing strain generation across linked nanosheet and nanoscroll geometries, tuning host strain through nanoparticle identity, extending strain-controlled catalysis to reactions such as ammonia synthesis, and exploring boron nitride nanoscrolls as more thermally robust confinement hosts.