In Situ Characterization of a Single Catalytic Nanoparticle

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0729630Collins, Philip A poor understanding of catalytic activity currently limits the efficiency with which new catalysts can be discovered, optimized, and implemented in commercial applications. This project describes a focused effort to measure the chemical activity of single catalytic nanoparticles. By measuring particles singly, the consequences of composition, size, and substrate support can be precisely determined, in order to uncover mechanisms which make some catalyst systems more effective than others. The research is underpinned by new experimental techniques in which single catalytic particles are integrated into operational, three-terminal nanoscale circuits. The PI's research group at UC Irvine specializes in the fabrication, characterization, and chemical modification of circuits based on carbon nanotubes, and has demonstrated the ability to build circuits in which the resistance is dominated by a single platinum, palladium, or nickel particle. Current expertise includes the ability to produce a point defect in a pristine carbon nanotube, tailor the chemistry of that defect, and then nucleate and grow one particle at that site. The project goal is to employ these nanocircuits to monitor the chemical activity of catalyst particles in situ and in real time. The circuits are exquisitely sensitive to their attachments, and chemical readout from single Pd and Ni particles has already been demonstrated in liquids and gases. The project will explore both catalytic and electrochemical reactions occurring at the surfaces of various metal, intermetallic, and metal oxide particles. The intellectual merit of this research program is a focused effort to quantitatively differentiate between very similar catalytic systems. For example, one objective is to distinguish the relative activity of differently-sized Pd particles. Another aim is to compare hydroxyl- and carboxylterminated carbons as catalyst supports. A third objective is to prepare dual-particle systems in order to study the importance of interparticle spacing. Each of these investigations directly addresses major shortcomings in common ensemble measurements and potentially provides an efficient route to new breakthroughs in catalysis research. This project will also have significant broader impact by accelerating the discovery process of high activity catalysts. If successful, this proposal will directly address process control and improve the predictability of catalyst systems. The project will also generate multiple opportunities for graduate training at UC Irvine and be reinforced by the PI's extensive teaching and outreach activities.