Hydrogen initiative: An integrated approach toward rational nanocatalyst design for hydrogen production. Technical Report-Year 1
- Univ. of Delaware, Newark, DE (United States)
The overall objective of this grant is to develop a rational framework for the discovery of low cost, robust, and active nano-catalysts that will enable efficient hydrogen production. Our approach will be the first demonstration of integrated multiscale model, nano-catalyst synthesis, and nanoscale characterization assisted high throughput experimentation (HTE). We will initially demonstrate our approach with ammonia decomposition on noble metal catalysts. Our research focuses on many elements of the Hydrogen Initiative in the Focus Area of “Design of Catalysts at the Nanoscale’. It combines high-throughput screening methods with various nanostructure synthesis protocols, advanced measurements, novel in situ and ex situ characterization techniques, and multiscale theory, modeling and simulation. This project directly addresses several of the long-term goals of the DOE/BES program. In particular, new nanoscale catalytic materials will be synthesized, characterized and modeled for the production of hydrogen from ammonia and a computational framework will be developed for efficient extraction of information from experimental data and for rational design of catalysts whose impact goes well beyond the proposed hydrogen production project. In the first year of the grant, we have carried out HTE screening using a 16 parallel microreactor coupled with an FTIR analysis system. We screened nearly twenty single metals and several bimetallic catalysts as a function of temperature, catalyst loading, inlet composition, and temperature (order of 400 experiments). We have found that Ru is the best single metal catalyst and no better catalysts were found among the library of bimetallics we have created so far. Furthermore, we have investigated promoting effects (i.e., K, Cs, and Ba) of the Ru catalyst. We have found that K is the dominant promoter of increased Ru activity. Response surface experimental design has led to substantial improvements of the Ru catalyst with promotion, especially at lower temperatures. It has been found that the promoting effect is not limited to K but extendible to some other alkaline metals. In addition, we have studied a number of synthesis variables, including the effects of support, solvent used, calcination temperature and time. It has been found that solvent and support could have an important effect on activity. Advanced characterization of the Ru/K promoted catalyst has been carried via SEM, TEM, selected-area electron diffraction, and energy dispersive x-ray spectroscopy. It has been found that the Ru catalyst is composed of agglomerates, whereas the K-promoted catalyst of “nanowhiskers” with a KRu4O8 hollandite structure. Our detailed characterization studies strongly suggest for the first time a strong correlation between hollandite formation and the high activity of Ru catalyst. Future work should provide stronger evidence of this correlation and may enable us to further improve the catalyst. A number of microkinetic models for single metals have been developed and a methodology for linking models for bimetallic catalysts in a thermodynamically consistent manner has been implemented. This enables us for the first time to start exploring multi-site catalysts, using either mean-field or Monte Carlo approaches, and filling the materials gap from single crystals to supported catalysts. In addition, we are developing a multiscale model-based design of experiments methodology. This framework employs multiscale-based models combined with global search in experimental parameter space, identification of novel experimental conditions that maximize the kinetic information content, followed by statistical analysis that can guide the next iteration of experiments.
- Research Organization:
- Univ. of Delaware, Newark, DE (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-06ER15795
- OSTI ID:
- 901553
- Report Number(s):
- DOEER15795
- Country of Publication:
- United States
- Language:
- English
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