Computational studies of heterogeneous and homogeneous catalysis by late transition medals
To design new catalysts that meet the environmental, materials and energy concerns of modern society, it is vital to understand the fundamental mechanisms involved in catalytic reactions. This thesis focuses on using quantum mechanical methods to determine the mechanisms for several critical catalyt...
| Summary: | To design new catalysts that meet the environmental, materials and energy concerns of modern society, it is vital to understand the fundamental mechanisms involved in catalytic reactions. This thesis focuses on using quantum mechanical methods to determine the mechanisms for several critical catalytic processes in chemical industry.
Late transition metals are widely used as heterogeneous catalysts involving organic substrates. To lay a foundation for developing an orbital view useful for reasoning about surface reactions, we have developed the interstitial electron model (IEM) for bonding in platinum described in Chapter 1. To test the validity of the model cluster chosen to represent the surface, we studied the chemistry of C_1 and C_2 hydrocarbons, for which the most single-crystal experimental data is available, as described in Chapter 2.
In Chapter 3, we extend this model to the second and third row Group VIII transition metals (Ir, Os, Pd, Rh, Ru) and develop a thermochemical group additivity framework for hydrocarbons on metal surfaces similar to the Benson scheme so useful for gas phase hydrocarbons. This provides a potentially powerful technique for deriving a mechanistic understanding on complex hydrocarbon reactions on catalytic surfaces, applicable to hydrocarbon reforming processes.
An advantage of direct methanol fuel cells (DMFCs) over the internal combustion engines is to avoid the environmental damage caused by the latter. Chapter 4 describes our studies on electrocatalysis of methanol oxidation in direct methanol fuel cells. In particular, we focus on the role of different metals at the anode as alloys and as promoters for various aspects of the reaction converting methanol and water to CO_2 and energy.
One of the most important challenges is to find ways to utilize the enormous resources in methane around the world as the fundamental feedstock for the chemical and energy industries. Perhaps the most promising progress in developing low-temperature highly selective homogeneous catalysts have been the Hg and PtCl_2 catalysts from Catalytica. Chapter 5 reports our studies on the stability, thermodynamics, and reaction mechanism of the PtCl_2 catalysts, with suggestions of possible modifications necessary to make this process economic.
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