Optimization of catalyst particle size and morphology, the prime drivers of catalyst functionality, is performed by modifying synthesis parameters of analogous systems until desired catalytic properties are obtained. However, this generates a limited understanding of the role of the individual parameter on catalyst properties. Factorial design of experiments (DOE), on the other hand, permits a thorough investigation of synthesis parameters, and provides insights into both the individual effects and their synergism. We report here on recent work in our lab employing DOE to investigate the role of synthesis parameters on particle size, morphology, and final figure of merit in cobalt-based catalysts.We employed a two-level full factorial design to screen the effect of varying synthesis temperature, temperature ramp time, and the precursor, reducing agent, and capping agent concentrations on the particle size in Co-based bimetallic catalysts. It was determined that, while precursor concentration was universally important, the miscibility of the second metal correlated to either the capping agent or the synthesis temperature determined particle size. The resulting response surfaces were used to identify synthesis conditions resulting in mono-disperse alloy nanoparticles with controlled average size. The bimetallic catalysts were demonstrated to outperform non-optimized Co-TM catalysts using NaBH4 hydrolysis as a model reaction. Further investigation of the synthesis temperature led to altering catalyst morphology from nanoparticles to nanorods. The two catalyst morphologies lead to distinct differences in stabilities during Fischer-Tropsch synthesis. The nanorods were observed to exhibit reversible oxidation on the surface, termed self-healing, resulting in indefinite catalytic activity during water-enriched FTS.

Exploration of the role of synthesis on catalytic performance of cobalt-based catalysts guided by factorial designs

248th National Meeting (2014)

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