In this project funded by the Chemical Catalysis Program of the Chemistry Division, Professor John Anderson of the Department of Chemistry at the University of Chicago is studying the catalysis of oxygen evolution from water. At the center of most renewable energy schemes is the utilization of hydrogen fuel. The simplest environmentally benign approach to the production of hydrogen fuel involves the catalytic splitting of water into hydrogen and oxygen. The oxygen-forming portion of this process has been considered the most challenging transformation to promote. While it is known that two oxygen atoms must combine and bond together during catalysis to form oxygen, the precise mechanism through which this bond formation occurs is currently unknown, limiting the development of more efficient catalysts. Professor Anderson is synthesizing and studying the catalytic activities of compounds that contain transition metal atoms in order to provide a new design principle for oxygen evolution catalysis. Outside of the laboratory, Professor Anderson is engaging in collaborations with schools in Chicago's south side neighborhoods. He is helping students to prepare for science fairs and city-wide science competitions, and has created a summer internship for local high-school students to provide them with a "hands-on" science laboratory experience. The aim of these efforts is to enhance the science education of a typically underserved group of students and to encourage their interest in careers in STEM fields.
In this project, Professor Anderson is investigating the details and scope of a radical coupling mechanism for oxygen-oxygen bond formation in oxygen evolution catalysis by transition metal systems. This mechanistic hypothesis has recently gained increased favor, but there has been little investigation into either the degree of radical character on oxo ligands or the agency of radical character in oxygen-oxygen bond formation. A low-coordinate pseudo-tetrahedral complex geometry will allow for the synthesis of metal-oxo compounds that are partially stabilized by metal-oxygen multiple bond character. These species are proposed intermediates in catalytic oxygen evolution, and this geometry is expected to engender unusual spin states and electronic structures that may be relevant for catalysis. Following their synthesis, these complexes are being characterized to determine the degree of spin delocalization onto the oxo ligand via a variety of techniques such as EPR spectroscopy, ENDOR spectroscopy, and various X-ray experiments and spectroscopies. Thorough characterization is enabling detailed structure-function studies. The relative viability of these complexes to engage in oxygen-oxygen bond forming catalysis, particularly with regards to their oxygen-centered spin density, will both inform current mechanistic hypotheses and provide a new design principle for oxygen evolution catalysis.
