Platform molecular materials and surfaces for solar fuels generation

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The proposed research program seeks to understand how systems can use sunlight to generate charges to drive catalysts for solar fuels generation. This goal is realized through building an understanding of and characterizing the basic phenomena of solar energy conversion dynamics, by engineering and synthesizing nano- and mesoscale architectures with targeted functionality, and by combining solar energy conversion phenomena across time and space. More specifically, this proposal seeks to answer the following central questions: how does the structure of molecular materials determine the efficiency of light capture and charge transport, and how can material properties be modified to take advantage of hierarchical assembly for systems scalable from the nano- to the mesoscale? Solar fuels catalysis relies on single electron transfer events between a chromophore/catalyst and/or a substrate. To drive catalysis in bimolecular reactions that occur after photon absorption, careful redox leveling must be implemented across all components. In the first major focus of this work a hierarchical approach to designing, preparing, and characterizing solar fuels catalysts will be undertaken. While mechanistic investigations are often easier to carry out in homogeneous systems, heterogeneous catalysts benefit from increased stability and recyclability. A combination of both approaches involves the adsorption of molecular chromophores and known catalysts onto heterogeneous semiconductor surfaces. Few photoelectrochemical (PEC) cells that combine molecular catalysts, dyes and semiconductor surfaces exist, due to the array of variables that must be optimized to make a functioning dye sensitized photoelectrochemical device (DS-PEC).In the second major focus of this proposal, tandem DS-PEC devices will be developed utilizing a bottom-up approach. Semiconductors will be grown on surfaces and subsequently functionalized by adsorbing inorganic supramolecular chromophore-catalyst assemblies. Electrochemical measurements in the presence of light irradiation will confirm reduction or oxidation of catalysts present in proximity to the chromophores, while prolonged irradiation in the presence of catalytic amounts of either water or acid in a sealed electrochemical cell will yield measurable amounts of desired gasses (O2 and H2).The long-term vision of this work is to develop fundamental understanding coupled with materials and methods to engineer dramatically more efficient technologies for solar fuels production (e.g. conversion of CO2 to value added products, or the reduction of protons to hydrogen). Ultimately, this strategy affords the engineering of energy conversion systems operating with exceptional performance while mentoring a technically exceptional workforce capable of solving energy-related problems far into the future.