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Heterogeneous catalysts for renewable energy

SULI 1: Precious metals and metal alloys are important heterogeneous catalysts for renewable energy and materials. However, both of them have their limitations. Precious metals have low natural abundance and are expensive. Metal alloys have unstable surfaces due to surface segregation under reaction conditions, which renders the identification of active sites and the understanding of reaction mechanisms difficult. My research group will address these limitations by developing new intermetallic NP catalysts. Intermetallic compounds, which consist of two or more metallic elements, adopt specific crystal structures as well as electronic structures different from the constituent elements. The modified electronic structures of intermetallic compounds make them unique catalytic materials. It has been proposed that such compounds should be treated as new “elements” considering their potential in catalysis. The inherent properties of intermetallic compounds, stable and exhibit a large variety of structures, will help us to discover catalysts with stable surfaces, consisting of more abundant metals, to replace unstable alloy and precious metal catalysts.

SULI 2: Developing Functionalized Graphene for Biomass Conversion

The goal of this research project is to develop low cost catalysts based on graphene-derived nanomaterials, and use them to improve the efficiency of several key steps in biomass refinery. To make the cost of biomass derived fuels comparable, or lower than that of petroleum fuels, it is necessary to develop new catalysts and processes that can substantially improve the efficiency of biomass refinery. Two attractive biomass refinery processes, pyrolysis and hydrolysis of lignocellulose, usually give molecules containing high oxygen content, and thus low energy density to be used directly as fuel. Therefore, upgrading of the lignocellulose derived oxygenates is necessary for them to be fit in appropriated fuel classes (i.e., gasoline, diesel, or jet fuels). The general approaches for upgrading the oxygenates are to decrease their oxygen contents, and to build carbon-carbon bonds, targeting different fuel classes. Catalysts play a vital role in converting and upgrading biomass to fuels, and thus need to be studied extensively. Catalysts based on graphene-derived nanomaterials could greatly improve the efficiency of biomass conversion to liquid fuels, but they have not been systematically explored for this purpose. These improvements will substantially decrease the cost of biomass conversion.   

SULI 3: To control heterogeneous catalysis at atomic and electronic-level represents one of the most challenge research areas. Using metal organic frameworks (MOFs) as hosts of metal nanoclusters, we could reach an atomic and electronic-level control of heterogeneous catalysts. MOFs, as novel template materials for the synthesis of metal nanoclusters, have great potentials for catalysis due to their structural diversity, flexibility and tailorability, as well as high porosity. Compared to zeolite, the chemical environment of each cage/cavity of MOFs can be controlled at atomic-level by using different organic linkers. These different organic linkers or metal ion nodes of MOFs results different chemical environments. Nanoclusters, resident in these cages/cavities, would experience an atomic-level fine-tuned chemical environment, and thus exhibit different activity and selectivity in heterogeneous catalysis. During chemical conversion processes, reactants and reaction intermediates could also sense these chemical environments that could alter their adsorption energy and geometry, which will also affect the reaction activity and selectivity.

Program mentor: Wenyu Huang, Assistant Professor of Chemistry, Iowa State University