Articial Photosynthesis provides a way to produce high-value chemical fuels directly from sunlight thus storing the sun's power in chemical bonds. The key idea is to mimic photosynthesis processes found in nature in "artifcial leaves". The goal is to build stand-alone devices capable of converting solar irradiation into usable chemical fuels. Several examples and techniques have been proposed. The most promising approaches are water splitting devices producing hydrogen and oxygen, and CO2 reduction to produce carbon-based fuels.

Modelling and optimizing a water splitting device is a challenging tasks as processes such as absorption and catalytic conversion have to be optimized individually and the combined system must operate at maximum effiency to make the approach viable in todays energy markets. In water splitting devices the absorber material must not only provide sufficient light absorption of the sunlight, but simultaneously act as a catalyst for the hydrogen (or oxygen) evolution reaction. The high redox potential of 1.23 V required to drive this reaction either demands complex solar cell concepts such as multi-junctions to provide enough voltage or the development of new metal oxide semiconductors. Their advantages such as earth abundance, high voltages and catalytic properties usually comes at the expense of electric and optical properties. Similar to silicon based solar cells they show imperfect light absorption. Plasmonic effects can not only enhance optical absorption by increased light scattering, but also localize electromagnetic near  fields to drive surface reactions.

Plasmonics and finite element simulations. We investigate plasmonic devices and effects using finite element simulations. New promising concepts for water-to-hydrogen conversion are based on plasmonic resonances of 3D nanoparticle arrangements on catalytic surfaces. The research includes utilization of metamaterial resonances for tailored, enhanced electromagnetic near fields, allowing for increased plasmon-induced dissociation of hydrogen on noble metals.
 

Electromagnetic field distribution in the vicinity of plasmonic nanoparticles

 

This research is carried out in the framework of MATHEON supported by Einstein Foundation Berlin.