Custom Catalyst Resists Oxidation

Solid-state catalysts mediate a large fraction of commercial chemical reactions. Typically, these chemistry workhorses lose some of their ability to transform reactants to products as a result of various aging processes. One such process converts active metallic catalyst sites to inactive metal oxides. That undesirable change requires frequent chemical reactor maintenance, which is costly. A team led by Jason Hattrick-Simpers and Jochen Lauter­bach of the University of South Carolina, Columbia, report a strategy for avoiding that problem. In a proof-of-concept study, the team shows that cobalt-based catalysts that drive Fischer-Tropsch chemistry, a process for making synthetic fuels from CO and hydrogen, can be tailored to resist oxidation by water vapor, a common problem. The trick is selectively exposing oxidation-resistant crystal faces by preparing the catalyst as elongated nanorods instead of nanoparticles (Chem. Commun. 2014, DOI: 10.1039/c4cc01021c). Catalysis tests and spectroscopy analyses show that in contrast to cobalt-based nanoparticles, which become oxidized and lose catalytic activity quickly in the presence of steam, nanorods remain largely unaffected. The group attributes the oxidation resistance to the more favorable reduction potential of the nanorod surfaces relative to those of nanoparticles.