Towards Photoactive Membranes for Artificial Photosynthesis

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The project targets the integration of molecular compounds, i.e. photocatalysts and redox-active antenna dyes, into recently developed carbon nanomembranes for applications in, e.g., photocatalytic cells. This research on novel photoactive membranes for artificial photosynthesis will comprise different tasks from materials and physical chemistry: (i) development of novel carbon nanomembranes functionalized with benchmark electron donors, acceptors and photosensitizers; (ii) development of novel synthetic procedures for the fabrication of carbon nanomembranes with new functionalities, i.e. photosensitizers and electron donors/acceptors integrated within the membrane plane; (iii) developing a mechanistic understanding of light-induced elementary processes within the novel carbon nanomembranes and proof-of-concept photocatalytic hydrogen evolution from carbon nanomembranes functionalized with cobaloxime proton-reduction catalysts. The project aims at establishing the conceptual basis for the design of novel photoactive membranes for artificial photosynthesis. The supramolecular systems to be researched are based on molecularly thin carbon membranes, which can be specifically functionalized on either side of the membrane. In this project the focus will not (yet) be on device integration but on establishing the basic design principles and performing essential mechanistic studies on the elementary reaction steps underlying a potential use of the systems in photocatalytic water splitting. The carbon nanomembranes will be functionalized with Ru(II)-polypyridine-derived systems, which act both as the chromophores, i.e. the light-absorbing units, and the primary electron donors. In the envisioned design of the photoactive carbon nanomembranes the electron donors will be grafted onto one side of the molecularly thin membranes, while the opposite side of the membrane will be functionalized orthogonally by the corresponding acceptor units. Thereby, the formation of charge separated states is expected upon irradiation, whereas the photooxidized and photoreduced species are spatially separated by the nanomembrane. In order to enhance the lifetime of the charge separated state, and hence the 'usability' the photoseparated charges, we will adopt concepts from the design of molecular triads (i.e. acceptor-chromophore-donor) and design systems, in which the chromophore-side of the membrane is additionally equipped with electron donor units.