The pyro-electro-catalytic induced generation of hydrogen gas is an environmentally friendly and sustainable way to convert excess thermal energy into a storable form. The main idea is to make use of spontaneous polarization of pyroelectric materials that can be altered by temperature changes. Thus, surface potential changes and subsequent electron exchange with surrounding molecules can be induced. In this work, a fundamental model to describe the behavior of a thermally excited pyroelectric material in pure water is developed. The model combines the fields of pyroelectricity, electrochemistry, diffusion and semiconductor theory. After derivation, it was used to explore some basic questions on pyro-electro-catalytic hydrogen production and the accuracy was tested with experimental data. The results show that p/ε_r has to be balanced depending on the temperature gradient to maximize the hydrogen production. The validation of the experimental data revealed good agreement.

The wetting behavior was measured for Al₂O₃-C in contact with AlSi7Mg with a conventional sessile drop test (vacuum, 950 °C and 180 min) and a sessile drop test with a capillary purification unit (vacuum, 730 °C and 30 min). The conventional test yielded contact angles of around 92°, whereas the sessile drop measurement with capillary purification showed a strongly non-wetting behavior with a determined apparent contact angle of the rolling drop of 157°. Filtration tests, which were repeated twice, showed that the Al₂O₃-C filter possessed a better filtration behavior than the Al₂O₃ reference filter. For both filtration trials, the PoDFA (porous disc filtration analysis) index of the Al₂O₃-C filter sample was equal to half of the PoDFA index of the Al₂O₃ reference filter sample, indicating a significantly improved filtration performance when using Al₂O₃-C filter. Notable is the observation of a newly formed layer between the aluminum and the Al₂O₃-C coating. The layer possessed a thickness between 10 µm up to 50 µm and consisted of Al, C, and O, however, with different ratios than the original Al₂O₃-C coating. Thermodynamic calculations based on parameters of the wetting and filtration trials underline the possible formation of an Al₄O₄C-layer.

The rapid development of light-emitting-diode (LED) technology is attributed to its superiority over light sources of earlier generations. Although LED lamps, compared to compact fluorescent lamps, are considered less harmful to the environment, there is still no efficient solution to deal with them at the end of their lifecycle. The first part of the study provides a detailed characterisation of LED lamps, focusing on their most interesting component: the LED module. LED packages attached to the module are highly enriched with Ga, In, Pd, Ag, Au, Sr, Y, Ce, Eu, Gd, and Lu, with the content of each element varying greatly depending on the LED technology. In the second part of this research, two new approaches for liberation and concentration of valuable components from LED modules are presented and compared: a chemical route and a thermal route. The chemical treatment leads to a highly selective separation of LED chips and encapsulation. Enrichment factors up to about 125 are achieved, and a concentrate is obtained containing approximately 14 wt% of the aforementioned valuable components. However, the process requires aromatic solvents, which are viewed as toxic. The thermal treatment results in separation of the aluminium heat sink from all other components of the LED module. Enrichment is approximately ten times lower, but the approach is technically feasible.