Chemistry Weekly Seminar- PhD Candidate Sudeesh Veeranmaril

Title:

Designing Sinter-Resistant Au Clusters for Catalysis

Abstract:

Catalysis by metal clusters (~1 nm in size) has attracted special attention owing to their excellent catalytic activity. Synthesis of metal clusters can be achieved by using thiolate ligands as a stabilizing agent. Metal clusters such as Au₂₅L₁₈ have a core-shell morphology in which Au-thiolate staple motifs protect a central Au core. However, the protecting ligands not only stabilize the structural integrity of Au₂₅ clusters, but can also block the active sites that are needed for catalytic reactions. To achieve strong catalytic performance, Au catalysts can be activated by the removal of stabilizing agents around the gold clusters. However, this activation process often leads to sintering of metal clusters and a loss of active surface area. In this talk, I will discuss several strategies for improving the thermal stability of Au cluster catalysts during the thermal activation process. Silica encapsulation and atomic layer deposition (ALD) of alumina over Au₂₅(SR)₁₈ clusters will be discussed. In this research work, Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was utilized to analyze structural changes of the Au clusters upon heating, and In-situ HRTEM was used to monitor sintering of Au catalysts while heating under an oxygen atmosphere.