ABSTRACT

Novel catalyst design by tailored integration of nanomaterials with larger porous scaffolds

Catalysts are an enabling technology critical to key industrial sectors such as water, energy, chemicals, and pharmaceuticals. The effectiveness of any solid catalyst strongly depends upon the availability of surface reactive sites. Nanomaterials (that have dimensions in 1-100 nm range) provide significant advantages in this regard because they offer exceptionally higher surface area per unit mass compared to conventional materials. However, nanocatalysts are generally deployed as loose powders or colloids that can easily disperse into the surroundings, posing serious health and environmental risks. The goal of this EAGER award project made to Professor Sharmila Mukhopadhyay at Wright State University is to explore if this dilemma can be resolved by combining the advantages of nanomaterials with the structural integrity of robust solids. In natural biological surfaces such as intestinal and bronchial linings, an extremely high level of interaction in a compact space is enabled through "hierarchical" and "hybrid" architectures, in which larger scaffolds provide mechanical support and progressively smaller specialized attachments offer additional functional properties. This project will explore if and how the same concept can be adapted to catalyst design, starting with porous solid scaffolds and enhancing them with controlled sequence of strongly adhered nano-scale catalytic materials such as carbon nanotubes, oxide coated nanotubes, and metal nanoparticles. The payoff can be very high, since it will enable creation of innovative surface-driven devices including catalysts, sensors and energy storage components. Another benefit from this project will be educational components relating nanotechnology with catalysis and environmental sustainability. All participants in this project are involved in student mentoring as well as development of K-12 educational modules. Outreach programs that will benefit from this project include pre-college offerings for disadvantaged students and training camps for STEM Teachers.

The goal of this project is to provide in-depth understanding of processing and properties of hierarchical hybrid materials, in which well-tailored distribution of nanoscale components of varying dimensions are anchored on larger porous scaffolds. Scaffold support materials envisioned are foams or fabric of carbon, whose specific surface areas are increased by several orders of magnitude through controlled attachment of carpet-like arrays of carbon nanotubes. These nanotubes may be coated with oxide layers for increased surface wettability and/or improved catalyst-support interactions. Finally these nanotube-enhanced scaffold surfaces will be functionalized with catalyst nanoparticles such as palladium. The materials synthesized will be used to degrade a model water-borne pollutant, trichloroethene (TCE), which is widely used by industry and known for its toxicity and persistence in ground-water. This project will answer three very basic questions relevant to surface-active devices: (i) Is it possible to attach multiple nano-catalysts to a single robust solid with sufficient control? (ii) Would the integrated hybrid material retain or improve the benefits of each component? If so, how does the integrated solid compare with its components and with conventional catalyst pellets and powders? (iii) Are these structures suitable for prolonged use? The answers to these questions can provide the groundwork for integrating advanced nanocatalysts into larger solid devices.

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