| 초록 |
Separation of photogenerated electron-hole pairs in semiconductor is one of the key processes in photocatalysis. Heterostructured nanocrystals of semiconductors with a type-II bandgap offset facilitate the dissociation of excitons. Photocatalytic activity improves when the photogenerated electrons and holes become available to participate in reduction and oxidation on the surface, respectively. Therefore, prolonged electron-hole recombination time, or exciton lifetime, and heterostructures with both reduction and oxidation sites available on the surface are deemed to enhance photocatalytic activity. In this presentation, we describe the design of heterostructure nanocrystals based on Pb and Cd chalcogenides showing ultralong recombination lifetime, amorphous oxide shells that protect the nanocrystals from oxidation and enhance separation of photogenerated charge carriers. A principle that underlies the design strategy is to synthesize nano-sized junctions with electron-hole separation, with the structure of “open” geometry, such as tetrapods. Also, the surface photochemistry will be discussed in the context of defect passivation and photocatalysis using the semiconductor nanocrystal quantum dots. The hydrogen production rate is comparable to the record values reported thus far, and we will discuss the possibility of expanding the nanocrystal design strategy for CO2 reduction and other photocatalysis. |
