Ryan J. Gilliam

Part 1—Structure-Sensitivity of Nanoparticle Catalysts: Relating Current Theories to Experimental Data

This work investigates the current theories that have been used to explain the particle size effect on electrocatalytic activity. In particular, this work focuses on electronic structure effects, geometric shape effects, crystallographic orientation effects, support structure effects, and the concept of territory theory. To investigate these theories, gold and nickel–phosphorus nanowire arrays have been used as model systems for electrocatalytic testing of the hydrogen evolution reaction in basic medium. In this study, the current particle size effect theories cannot adequately account for the observed structure-sensitive trends that are exhibited in the aforementioned systems. This work systematically looks at each of these different theories and discusses new possible factors that could serve as a foundation for a new theory on structure-sensitive catalysis.

Part 2—Impacts of Electrolyte and Reactant Size on Structure Sensitivity in Electrocatalysis: A Geometric Approach

In previous work performed by the current authors, an in-depth analysis of the current theories relating particle size to electrocatalytic activity was undertaken. In that work, electronic structure effects, geometry and crystallographic orientation effects, territory theory and support structure effects could not account for the structure sensitivity exhibited in the experimental data. This study builds on that previous work and investigates the impact of electrolyte conditions and reactant size on the structure sensitivity of Au nanocatalysts for multiple electrochemical systems. The Fe3+/Fe2+ reaction was studied for multiple reactant sizes in a wide range of electrolyte conditions. There was a clear impact of reactant size on the critical size at which deviation from bulk electrocatalytic performance takes place. These findings were used to develop a geometric model, which could account for the increase in electrocatalytic activity observed below critical nanoparticle diameters.