The aim of this project is to synthesize and assemble novel nanomaterials for the purpose of water splitting through a rational design process. To achieve efficient water splitting we want to mimic photosynthesis in green plants by using the so-called Z-scheme. Briefly, the Z-scheme consists of two photosystems abbreviated as PSI and PSII. When the photosystems are illuminated with light, electrons both in PSI and PSII are excited to a higher level. Due to the specific band offset in these photosystems the photogenerated electrons in PS II are transferred to the highest occupied molecular level of PS I. These electrons then recombine with holes photogenerated at PS I. While the photogenerated electrons in PS I participate in reduction of protons to produce hydrogen, the holes in PSII oxidizes water molecules, producing oxygen. By mimicking such a Z-scheme, we expect the probabilities of charge recombination to decrease significantly, resulting in more efficient hydrogen generation.
We want to design novel nanomaterials by modifying a Z-scheme type system with the following changes: 1) to engineer an interface between two different nanomaterials or to link them using a solid state electron mediator, 2) to synthesize a single heterostructure material that meets the band offset requirements, and 3) to selectively deposit metal nanoparticles only on the semiconductor phases designated as PSI. Introducing modifications into a Z-type-scheme will offer the capability of using semiconductors with band gaps less than thermo-dynamical limit (1.23 eV/pH=0) for water splitting and improve photostabilities of many catalysts. The project will primarily aim at boosting the photocatalytic activities of nanomaterials for overall water splitting i.e. attaining a quantum yield above 6.3 % at 420 nm. From the perspective of commercialization, templating systems combined with wet-chemistry synthetic routes will be developed for the preparation of the nanomaterials.
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