Collaborative Research: Regulating homogeneous and heterogeneous mechanisms in six-electron water oxidation

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Professor John A. Keith of the University of Pittsburgh and Professor Maureen H. Tang of Drexel University are supported by the Chemical Catalysis Program of the Division of Chemistry to conduct a combined experimental/theoretical study to understand the formation of ozone through the electrocatalytic oxidation of water. The largest use of ozone (O3) is in the preparation of pharmaceuticals, synthetic lubricants, and other commercially-useful organic compounds. Ozone is also used to kill bacteria in municipal drinking water. Electrochemical ozone production involves heterogeneous (on electrode surfaces) and homogeneous (in solution) chemical steps. Specifically, the study seeks to understand how and why this process occurs the way it does through the use of computational catalysis modeling in tandem with experimental measurements. Once the mechanism is established, recently developed computational high-throughput screening methods will be used to theoretically design and experimentally validate catalysts for ozone production. The project is expected to deliver fundamental knowledge on electrocatalytic reactions. Success is expected to satisfy the basic societal need for such a commodity. Students are trained in combined experimental and theoretical chemistry research tools. Middle schools in urban areas with high populations of underrepresented groups are targeted with outreach plans. Existing activities that leverage the facilities of the Office of Diversity and Drexel's Lindy Center are continued and expanded. The project addresses the production of ozone via electrocatalytic oxidation of water. Specifically, the study seeks to understand how and why electrochemical steps occur in solution phase (homogeneously) and on an electrode surface (heterogeneously). Computational catalysis modeling while accounting for local solvation environments are combined with experimental ex situ electron paramagnetic resonance studies, differential electrochemical mass spectroscopy, and photocatalysis techniques to develop a complete understanding of the electrochemical ozone production mechanism (EOP). Three basic scientific questions are addressed: 1) what is the key EOP intermediate that leads to ozone and how is it generated? 2) why do certain catalyst materials and configurations uniquely improve EOP selectivity? and 3) can improved mechanistic understanding lead to novel and improved EOP catalysts? This project is expected to lay important foundational work that is needed to understand fundamental electrocatalysis reaction mechanisms that involve homogeneous and heterogeneous steps. It is also expected to validate EOP as a means to sustainable production of ozone.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.