INVESTIGATION OF NANOCRYSTAL HETEROSTRUCTURES FOR PHOTOCHEMICAL HYDROGEN PRODUCTION

摘要

The growing need for energy harvesting that has minimal environmental impact has been recognized by scientists and society. One proposed solution is artificial photosynthesis, in which solar energy is converted directly into fuels. The process of solar fuel generation is complicated because it occurs in several steps: absorption of photons and subsequent generation of charges in the light harvesting material, transport of charges to a catalyst, and the catalyzed, multi-electron fuel-generating reaction. A major challenge of producing solar fuels is to control and optimize the rates of these steps. Due to their highly tunable properties, semiconducting nanocrystals (NCs) are promising light harvesting components of artificial photosynthetic systems. Previous work has demonstrated that complexes of CdS NCs and [Fe-Fe]-hydrogenase from Clostridium acetobutylicum produce H2 photochemically with quantum yields up to 20%, which is limited by competition between the rates of electron transfer (ET) to hydrogenase and electron-hole recombination in the NC. The photophysical properties of NCs can be controlled via localization of excited charge carriers in NCs where two different materials are epitaxially attached, known as heterostructures. Here we report a H2 producing system in which ZnSe/CdS or CdSe/CdS dot-in-rod heterostructure NCs are coupled to hydrogenase. Using time-resolved transient absorption spectroscopy, the relationships between NC structure, NC photophysics, and ET are elucidated. Since ET is a key step in efficient harvesting of solar energy by NCs, these fundamental studies will inform the design of future solar energy conversion architectures.