Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 11: Nanostructures at Surfaces I

O 11.2: Talk

Monday, March 31, 2014, 10:45–11:00, WIL C107

Tandem nanostructure for solar water splitting — •Stefan Bösemann, Liaoyong Wen, Fabian Grote, and Yang Xu — Ilmenau University of Technology, Institute of Physics & IMN MacroNano (ZIK), Prof. Schmidt-Str. 26, 98693 Ilmenau (Germany)

A promising solution to challenge the problems of renewable energies like absence of sufficient storage facilities and energy transportation is offered by water splitting. In order to separate water into hydrogen and oxygen, a theoretical energy of 1.23 eV is needed, which can be up to 1.6 - 2.4 eV considering overpotentials. Besides, the minimum of the conduction band of the active semiconductor has to be lower than the redox potential of H+/H2 and the maximum of the valance band has to be higher than the redox potential of O2/H2O. Furthermore, lights absorption and material stability in electrolytes are very important aspects in regarding to efficient solar water splitting. To fulfill these requirements with only one absorber, a semiconductor with a large bandgap is necessary and thus can only absorb a small fraction of the incident sunlight. Hence, it is essential for an efficient water splitting system to be constructed of more than one absorbing material with different bandgaps to utilize a larger fraction of the incoming light and generate O2 and H2 in a single device. We have developed a tandem structure consisting of two-sided ordered semiconductor nanorods by using anodic aluminum oxide (AAO) templates. The two-sided ordered tandem architecture enables not only the complete water splitting but also a large surface and consequently an increased light absorption and a high surface reaction area.