The objective of this Faculty Early Career Development (CAREER) Program award is to elucidate the atomistic mechanism of the reduction of metal oxides. Real-time in situ microscopy techniques (in situ ultrahigh vacuum scanning probe microscopy and in situ environmental transmission electron microscopy) are employed to make controlled microscopic observations of the reaction morphology, structure and chemistry of the oxide reduction by temporally and spatially resolved high-resolution imaging, diffraction, and spectroscopy. Experiments will be performed on the reduction of simple model system of copper oxides (Cu2O and CuO) through vacuum annealing and hydrogen gas, which will lead to clear interpretations and establishment of fundamental concepts. The dynamic in situ visualization will be correlated with theoretical modeling for obtaining essential insights into reaction active sites, transient states, mass transport mechanisms, reaction activation energies, and reaction pathways.
The study will lead to mechanistic understanding of the reduction mechanism of metal oxides in the regimes from the initial reaction stages of nucleation and growth to the later-stage macro-scale growth of the reduced oxide phase. The goal of this research is to develop a predictive and hierarchical multi-scale oxidation model that naturally links these different stages of the oxide reduction. Through the development of such a predictive model, the project will have major impact on materials processing for many practical applications such as catalysis, thin film growth, fuel reaction, gas sensing, and electronic device fabrication, where the oxide reduction plays a crucial role. Graduate and undergraduate engineering students will benefit through involvement in the research as well as the development of a virtual transmission electron microscope that is designed to remove conventional barriers hindering effectively learning electron microscopy. High school students and science teachers will be engaged to provide them firsthand research experience.
