Electron-Rich Oxide Surfaces

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NON-TECHNICAL DESCRIPTION: From catalysis to photovoltaics, metal oxide surfaces are commonplace elements of materials design. Metal oxides can be used as supports for catalysts. In photovoltaics, they constitute electrode materials. A trend in current research efforts is to find inexpensive modifications to metal oxides so that specific properties of the complex material can be obtained. This strategy is particularly relevant to the catalysis industry, in which the oxide support can be orders of magnitude less expensive than the catalyst. Enabled by state-of-the-art, high-throughput computer simulations and imaging/spectroscopy techniques, this project aims at finding energy-efficient and inexpensive modifications to oxides that can alter their electronic behavior to become electron rich. Electron richness is an interesting property of materials which can be used to boost catalyst performance as well as photovoltaic function. Research is carried out by training graduate and undergraduate students under the supervision of the PI and co-PI. Graduates typically find employment in the New Jersey chemical industry. This project contributes to a summer outreach program that trains high school students from low-income backgrounds in materials modeling and imaging. TECHNICAL DETAILS: The goal of the project is to devise simplified ceramic engineering processes to fabricate electron-rich gamma aluminum oxide (alumina) and titanium oxide (titania) surfaces. The goal is to achieve a high-level, atomistic understanding of dopants' local environment and stability when it is surrounded by an environment as complex as a partially hydrated oxide surface. Scientific investigations will involve a combination of quantum-mechanical calculations based on periodic density functional theory and materials synthesis, imaging, and spectroscopy. Alumina and titania nanoparticles of different sizes are being doped with phosphorus and nitrogen with the aim of placing the dopant in subsurface sites. In this way, interaction with atmospheric oxygen is inhibited. The combination of homogenous vs. surface-only doping and varying nanoparticle size are providing a clearer picture of the role of the bulk on the persistence of surface states and surface electron richness. On the theory side, high-throughput calculations are analyzing a large number of possible configurations of the alumina and titania surfaces, dopant location, and hydration level.