artificial photosynthesis
(rus. фотосинтез, искусственный)
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Sunlight energy conversion into chemical energy using synthetic supramolecular nanosystems.
Description
For the sustainable development of humanity, by 2050 people will have to produce 10 TW/h of clean energy, in other words, without greenhouse gas emissions. The most promising way of generating clean energy is to use solar irradiation. There are three main uses of nanostructures for solar energy conversion: 1) artificial photosynthesis using donor-acceptor supramolecular assemblies and clusters 2) photocatalytic production of hydrogen, and 3) solar cells based on nanostructured semiconductors.
An artificial photosystem to convert light energy into chemical energy should contain, like a natural one, three main components: the photoantenna, the reaction site and the energy storage system. The photoantenna absorbs light energy and then transmits it to the reaction site, where chemical reactions occur. In the photosystems of higher plants and cyanobacteria, chlorophyll molecules play such role.
In the natural photosystems, spatial, electronic, kinetic and thermodynamic parameters of all three components are optimised for the maximum quantum yield. In artificial photosystems, in addition to the highest quantum yield, it is necessary to achieve the greatest possible conversion of light into chemical energy. When designing each of those components, two questions should be answered: 1) what substances - chromophores, donors, acceptors shall they be composed of, and 2) how to assemble those materials into a single operating system? In fact, it is necessary to select the "building blocks" and find a way to bind them together.
The easiest way to resolve this problem is when dealing with artificial photoantennae (see also supramolecular photochemistry). Metalloporphyrins are taken as chromophores - tetrapyrrole metal complexes and their derivatives. The most popular are porphyrins with ions of zinc, magnesium, and platinum group metals, and free porphyrins, where the central metal atom is missing. Porphyrins are combined into a single photoantenna using supramolecular chemistry techniques, i.e., through non-covalent interactions or by covalent bonds (Fig.). Varying the space structure of the antenna and the composition of porphyrin side chains, it is possible to control the energy flow through the antenna.
The current status of artificial photosynthesis is that the problem has been fundamentally resolved for the synthesis of the individual components of the photosystem (photoantennae, the reaction site and the energy storage system) and how they are bound. The challenge now is to improve the performance of those systems while keeping their main advantage over natural ones, which is the organisation simplicity.
An artificial photosystem to convert light energy into chemical energy should contain, like a natural one, three main components: the photoantenna, the reaction site and the energy storage system. The photoantenna absorbs light energy and then transmits it to the reaction site, where chemical reactions occur. In the photosystems of higher plants and cyanobacteria, chlorophyll molecules play such role.
In the natural photosystems, spatial, electronic, kinetic and thermodynamic parameters of all three components are optimised for the maximum quantum yield. In artificial photosystems, in addition to the highest quantum yield, it is necessary to achieve the greatest possible conversion of light into chemical energy. When designing each of those components, two questions should be answered: 1) what substances - chromophores, donors, acceptors shall they be composed of, and 2) how to assemble those materials into a single operating system? In fact, it is necessary to select the "building blocks" and find a way to bind them together.
The easiest way to resolve this problem is when dealing with artificial photoantennae (see also supramolecular photochemistry). Metalloporphyrins are taken as chromophores - tetrapyrrole metal complexes and their derivatives. The most popular are porphyrins with ions of zinc, magnesium, and platinum group metals, and free porphyrins, where the central metal atom is missing. Porphyrins are combined into a single photoantenna using supramolecular chemistry techniques, i.e., through non-covalent interactions or by covalent bonds (Fig.). Varying the space structure of the antenna and the composition of porphyrin side chains, it is possible to control the energy flow through the antenna.
The current status of artificial photosynthesis is that the problem has been fundamentally resolved for the synthesis of the individual components of the photosystem (photoantennae, the reaction site and the energy storage system) and how they are bound. The challenge now is to improve the performance of those systems while keeping their main advantage over natural ones, which is the organisation simplicity.
Illustrations
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Supramolecular hexade simulating the reaction center connected to a photoantenna. Authors D. Gust, T. A. Moore, A. L. Moore, Arizona State University, USA [2]. |
Author
- Eremin Vadim V.
Sources
- Kamat Prashant V. Meeting the Clean Energy Demand: Nanostructure Architectures for Solar Energy // J. Phys. Chem. C. 2007. V. 111. P. 2834–2860.
- Gust D., Moore T. A., Moore A. L. Mimicking Photosynthetic Solar Energy Transduction // Acc. Chem. Res. 2001. V. 34. P. 40–48.
- Martin N., Sanchez L., Herranz M. A. et al. Electronic Communication in Tetrathiafulvalene (TTF)/C60 Systems: Toward Molecular Solar Energy Conversion Materials? // Acc. Chem. Res. 2007. V. 40. P. 1015–1024.