Electrochemistry and Electrocatalysis
New heterogeneous catalysts with improved activity, selectivity, and durability are crucially needed for many petroleum and energy related applications. Catalysts are central to energy conversion, materials synthesis, industrial chemistry, pollution remediation, biology, and even medicine. It is widely recognized that improved fundamental understanding of the chemical and physical processes involved in catalysis at the atomic level would drive collateral progress on many of these fronts.
Traditionally, new catalysts have been developed by brute-force "trial and error" approaches. Our laboratory is exploring a different approach: enhancing well-known current heterogeneous catalyst systems by doping the support on which the catalyst sits. This support-modification approach has the potential to substantially improve catalyst activity and durability, while simplifying catalyst processing.
The ultimate vision for this research, shown in Figure 1, is a next generation catalyst system purposely "engineered" using dopant mediated growth and stabilization. In comparison to the current approach (Figure 1a), the engineered catalyst system (Figure 1b) employs a purposely-doped carbon-nanofiber support decorated by catalyst nanoparticles. The dopants are used to controllably regulate the size, density, and distribution of the catalyst nanoparticles- in effect, the dopant atoms act as template sites or heterogeneous nucleation centers for the metal catalyst nanoparticles. In this engineered system, the dopant/catalyst interactions are optimized to "tether" the catalyst particles in place, thus providing improved resistance to catalyst migration and agglomeration (migration and agglomeration are undesirable as they lead to catalyst degradation over time). Finally, instead of pure single-phase catalyst nanoparticles, this engineered system employs core-shell nanoparticles to further improve catalytic activity and stability.
Figure 1. Current catalyst systems (left) compared to the envisioned "dopant engineered" catalyst system (right). In comparison with current catalyst sytems, dopant mediated growth and stabilization of catalyst nanoparticles may lead to a more homogeneous, durable, active, and selective catalyst system.
This work is supported by the U.S.Army Research Office under grant number: W911NF-07-1-0258, Capital Equipment number: W911NF-08-1-0292 and ACS Petroleum Research Fund award number: 48158-G10.