PCCP Seminar: Scott Anderson - University of Utah

Size-selected ElectroCatalysis, and Single Nanoparticle Surface Chemistry

Tsugunosuke Masubuchi, Chris Y. Lau, Abigail M. Friese and Scott L. Anderson

Different strategies are required to examine the effects of size on reactivity for sub-nanometer clusters and nanoparticles (NPs)  For clusters, we prepare model catalysts and electrodes by depositing mass-selected clusters on clean substrates in UHV.  For NPs, feedstock heterogeneity means that even clusters of identical size would have different distributions of surface sites.  Furthermore, the surface sites and associated chemistry change during reaction, often dramatically.  To understand this chemistry, we study a series of individual NPs, measuring the variations in initial reaction efficiency and its time evolution under reaction conditions.

The sub-nano cluster approach will be illustrated using aqueous electrochemistry for electrodes prepared by deposition of Pt_n on indium tin oxide (ITO), fluorine tin oxide (FTO), and graphite (HOPG) electrodes.  The effects of cluster size and electrode substrate will be demonstrated for the hydrogen evolution reaction (HER) and for alcohol oxidation, both of which depend strongly on cluster size, but differently.

The single NP chemistry approach will be illustrated using high temperature O₂ etching and C₂H₂ addition chemistry for carbon NPs of different feedstocks (e.g. graphitic, diamond, nano-onion, carbon black).  The efficiencies for the two reactions are correlated, both varying from NP to NP, and both varying under reaction conditions by up to three orders of magnitude, often fluctuating strongly.  The application to ultra-high temperature materials will be shown.