Holistic, cross-sector approach
The desired transformation of the energy supply of an industrialized nation such as the Federal Republic of Germany, from fossil-based to regenerative and renewable sources, combines the necessary reduction in greenhouse gas emissions with a reduction in dependence on energy and raw material imports. Such an energy and economic system is both sustainable and resilient. However, this requires completely new energy generation and energy storage systems as well as a holistic view beyond the individual forms of energy, so that an increase in the efficiency of the overall energy balance can be achieved through (local) sector coupling. In Py-Pho-Hybrid-Energy, materials and methods are to be developed for the first time on the basis of which smart modules can be produced. These modules are intended to enable the conversion of solar energy both in the form of the long-term chemical storage medium hydrogen and in the thermal energy (heat) generated per se. The massive increase in the overall energy balance achieved in this way is to be further enhanced by enabling targeted conversion into electrical energy.
Semiconductor-ferroelectric hybrid membranes for innovative H2 generation
Current systems for producing green hydrogen from solar energy combine photovoltaic modules with electrolysers so that two independent processes take place separately – the conversion of solar energy into electrical energy and then its use to split water into hydrogen and oxygen. In photocatalysis, on the other hand, sunlight is used directly to produce hydrogen. This naturally offers the advantage of increased system integration, but its efficiency is currently far too low. One of the main reasons for this is the inefficient separation of the optically excited charge carriers, i.e., electrons and holes. In order to increase the separation of the electrons and holes and at the same time force them to the surface of the photocatalyst, pyroelectric fields are being used for the first time in Py-Pho-Hybrid-Energy. For this purpose, innovative hybrid membranes are synthesized in such a way that the photocatalytic semiconductor phase is present next to a ferroelectric phase. After polarization of the ferroelectric phase, a pyroelectric field is generated via a temperature gradient, which also penetrates the semiconductor phase and thus initiates charge carrier separation. The spectral range of sunlight, which is unsuitable for photocatalysis, is used to generate the necessary thermal gradient. In this way, the usable solar spectrum is massively extended compared to photovoltaics, but also to well-known photocatalysts, as the absorbed thermal radiation can then also be used as a heat source. The greatly increased overall efficiency can be further increased and specifically adapted by converting the stored thermal energy into electrical energy using the inverse pyroelectric effect of the ferroelectric phase.
Construction of a Phy-Pho-Hybrid-Energy module as a prototype for the assessment of potential
In Py-Pho-Hybrid-Energy, not only are various membrane concepts and designs being pursued and characterized, but the first prototype of a module is also to be realized. This will be used to determine characteristic values that can be used to estimate the potential with the help of modulation, especially with regard to the overall energy balance across sectors. On this basis, concepts for possible exploitation, e.g. in the form of a spin-off, will be developed. The main research work is carried out in the Optical Excited (Nano-)Hybrid Systems working group at the Institute of Technical Chemistry and Environmental Chemistry at Friedrich Schiller University Jena. In addition, there is cooperation with associated partners from the Center for Energy and Environmental Chemistry Jena and the Ernst Abbe University of Applied Sciences Jena in order to ensure the necessary breadth of research work.
