Nanotechnology has become an indispensable element of material engineering for energy related applications, and in particular catalysis. Efficient and effective energy harvesting and storage greatly benefit from advantages of controlling materials at the nanoscale. Catalysis has become a key issue in solving many of today's energy challenges. Multidisciplinary advances from chemistry, physics and materials science have provided deep insight into catalyst synthesis, structural and compositional modification, and mechanistic understanding with molecular and atomic-level precision. At the nanoscale, the surfaces or interfaces of a catalytic material structure strongly influence the physical and chemical properties of the material thanks to high surface-to-volume ratio. More interestingly, upon decreasing size, there is an associated increase in the relative number of (less coordinated) active sites located at the edges or corners of a nanostructured surface, which can play a major role in property modification. This is especially for those properties mainly originate from the surface, such as catalysis, which we use to our advantage in order to engineer more powerful catalysts and other energy enabling materials.
- Metalic Nanocatalysts. The formation mechanisms and the correlated composition structure-dependent catalytic properties of metallic (and multi-metallic) nanocatalysts have a significant impact on catalytic properies. We have successfully developed approaches to various shape and composition controlled bimetallic nanocatalyst and studies their enhanced catalytic properties. Porous structures are also used as a means to enhance surface properties of a catalyst and have been explored in both pure metal and alloy forms.
- Catalyst Supports. In addition, we have explored the interfacial interactions between the catalysts and the catalytic support to further enhance the catalytic properties of various catalysts. In one specific example, we demonstrate that by creating a composite graphene-active carbon composite support, the life time of the Pt catalyst can be greatly improved, leading to ca. 90% of the active remaining electrochemical surface after 20000 cycles compared to the less than 50% for commercial Pt/C catalysts. In another approach, we explored graphene as new catalytic support platform to enhance catalytic performance.
- Graphene Enhanced Catalysis. Graphene's extended 2D structure with rich p electrons can be used as an effective catalytic support. By conjugating graphene with metalloporphyrin molecules, we more recently created a new generation of highly effective biomimetic catalysts with catalytic activity approaching that of natural enzymes. We also developed a Hemin-Graphene (H-GN) composite catalyst, wherein in the graphene-hemin composite catalytic structures, where in hemin catalyst molecules were attached onto chemically exfoliated graphene via π-π interaction in the catalytically active monomer form. More importantly, this work was highlighted by a high conversion rate (over 50% converted) with high selectivity towards benzoic acid (~98% yield). This approach offers an alternative oxidative catalyst with higher specificity and feasibility in industrial applications.
- Fuel-Cells and Energy Conversion. Biofuel cell performance can be improved through understanding the electron transport in enzyme-based electrodes and systematic investigations of the nanoscale electron transport in biofilms of single- and few-cell assemblies of electrogenic bacteria such as Shewanella oneidensis and Geobacter sulfurreducens.