In this project funded by the Macromolecular, Supramolecular and Nanochemistry program, Mohammad Omary of the University of North Texas (UNT) is developing a new group of compounds for use as catalysts in alternative energy technologies. The compounds serve to accelerate the rate at which water is decomposed to hydrogen and oxygen, releasing the energy that once held the hydrogen and oxygen atoms together in each water molecule. The compounds being developed in this project are expected to have greater stability than existing materials in use, thus extending the practicality of this promising new source of alternative energy. The project is strengthening several existing academic/government/industrial collaborations between UNT and other US universities, national laboratories, and private sector entities as well as some existing and new international collaborations. The research is having a broader impact on energy-related science through the development of promising new technologies.
In this project, a series of phosphorescent complexes with various molecular- and nano-structural complexity are being investigated for their potential use as photocatalysts for water splitting. New photocatalyst candidates based on metal-organic compositions are being developed to engender greater material stability under practical environments in the presence of water and sunlight. The project focuses on a new design of practical multi-electron photocatalyst candidates that can operate in an aqueous instead of organic or mixed organic/aqueous media. The intent is to target water splitting in an efficient, environmentally-responsible manner using catalysts that operate homogeneously, or heterogeneously via solid films in order to increase ruggedness, concentrate the active material, and utilize intermolecular interactions to potentially sensitize cooperative electron transfer. Water solubility, while maintaining high luminescence quantum yield and long phosphorescence lifetime, is a highly desirable attribute for outer-sphere multi-electron photocatalysis. These conditions are satisfied by multiple embodiments of the macromolecular, supramolecular, and nanomolecular complexes that the Omary group is developing in this project in an effort to improve the state of the art of current water splitting photosensitizers. For inner-sphere processes, mono- and multi-nuclear complexes are designed to act as energy reservoirs for 6-12 photoelectrons in some solution compositions, whereas some solid photocatalysts have the potential to provide an almost infinite reservoir of electrons. These hypotheses are being assessed by examining the photophysical, photochemical, and electrochemical properties of complexes possessing ten or eight valence electrons as a function of concentration in solution or doping in thin films vs. the crystalline solid state.
