Publications

The materials genome initiative (MGI) aims to accelerate the process of materials discovery and reduce the time to commercialization of advanced materials. Thus far, the MGI has resulted in significant progress in computational simulation, modeling, and predictions of catalytic materials. However, prodigious amounts of experimental data are necessary to inform and validate these computational models. High-throughput (HT) methodologies, in which hundreds of materials are rapidly synthesized, processed, and characterized for their figure of merit, represent the key experimental enabler of the theoretical aspects of the MGI. HT methodologies have been used since the early 1980s for identifying novel catalyst formulations and optimizing existing catalysts. Many sophisticated screening and data mining techniques have been developed and since the mid-1990s, this approach has become a widely accepted industrial practice. This article will provide a short history of major developments in HT and will discuss screening approaches combining rapid, qualitative primary screens via thin-film techniques with a series of quantitative screens using plug flow reactors. An illustrative example will be provided of one such study in which novel fuel-flexible sulfur tolerant cracking catalysts were developed. We will then illustrate a path forward that leverages existing HT expertise to validate, provide empirical data to and help guide future theoretical studies.

Traditionally, the synthesis of CoFe nanoparticles with tunable particle sizes and narrow particle size-distributions is accomplished via the use of expensive and air sensitive precursors and strong non-polar capping agents. Such strong capping agents can be difficult to remove from the nanoparticles and thus render them catalytically inactive. We report a novel solution-based methodology to synthesize CoFe alloy nanoparticles with narrow size-distributions using a combination of robust and inexpensive metal precursors and an easily removable polar capping agent. High resolution transmission electron microscope images show that the CoFe alloy nanoparticles are well crystallized, and the particle size is tunable from 9 to 24 nm while keeping a particle size standard deviation of 10%. The CoFe alloy nanoparticles show superior activity for NaBH4 hydrolysis compared with the best-known CoFe catalysts. This work represents a substantial improvement in the synthesis of transition metal nanoparticles, opening the pathway for their application to a number of technologically important catalytic applications.

Reverse micelle synthesis was used to improve the nanoparticle size uniformity of bimetallic Pt/Ni nanoparticles supported on γ-Al2O3. Two impregnation methods were investigated to optimize the use of the micelle method: (1) step-impregnation, where Ni nanoparticles were chemically reduced in microemulsion and then supported, followed by Pt deposition using incipient wetness impregnation, and (2) co-impregnation, where Ni and Pt were chemically reduced simultaneously in microemulsion and then supported. Transmission electron microscopy (TEM) was used to characterize the particle size distribution. Atomic absorption spectroscopy (AAS) was used to perform elemental analysis of bimetallic catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were utilized to confirm the formation of the Pt–Ni bimetallic bond in the step-impregnated catalyst. CO pulse chemisorption and Fourier transform infrared spectroscopy (FTIR) studies of 1,3-butadiene hydrogenation in a batch reactor were performed to determine the catalytic activity. Step-impregnated Pt/Ni catalyst demonstrated enhanced hydrogenation activity over the parent monometallic Pt and Ni catalysts due to bimetallic bond formation. The catalyst synthesized using co-impregnation showed no enhanced activity, behaving similarly to monometallic Ni. Overall, our results indicate that reverse micelle synthesis combined with incipient wetness impregnation produced small, uniform nanoparticles with bimetallic bonds that enhanced hydrogenation activity.

Palladium addition to silver catalysts for ethylene epoxidation increases both catalyst activity and selectivity to ethylene oxide. These results confirm the predictions from density functional theory calculations that Pd–Ag bimetallics should improve selectivity relative to unpromoted silver. The performance of Pd–Ag catalysts is similar to that of Cu–Ag catalysts investigated previously, although the maximum selectivity obtained for the optimum Pd–Ag catalyst in the present study exceeds that achieved with Cu–Ag catalysts. Although there is evidence for greater complexity in the structure of these catalysts than has been incorporated in DFT models, these results provide an important additional example of catalyst identification and design from first principles.

The NH3-SCR activity of the small-pore zeolites, Cu-SSZ-13, Cu-SSZ-16, and Cu-SAPO-34, is investigated using a high-throughput reactor system. These copper exchanged small-pore zeolites have high SCR activity between 150 and 500°C and are shown to be much more hydrothermally stable than the medium-pore zeolite, Cu-ZSM-5. The degree of copper exchange, the dimensionality of the framework, and heteroatom framework substitution all impact the SCR activity and hydrothermal stability of the materials. Of the small-pore zeolites tested, Cu-SSZ-13 and Cu-SAPO-34 display superior SCR performance, both before and after high-temperature hydrothermal treatment.