In Search of the Holy Grail of Photoelectrochemistry A Study of Thin Film Electrodes for Solar Hydrogen Generation

Sammanfattning: Hydrogen is a wanted energy carrier in a future society less dependent of fossil fuels. This thesis investigates the possibilities of using solar energy to convert water into hydrogen and oxygen, so called artificial photosynthesis. Through this work multiple inexpensive and stable thin film semiconductor electrodes have been produced and used as solar energy absorbers and active sites for direct watersplitting in photoelectrochemical cells. The electrodes have mainly been of nanostructured metal oxide character but also nitrides have been studied. Detailed back ground theory on photoelectrochemistry of semiconductors for hydrogen evolution is given in the summary of the thesis.Nanostructured WO3 electrodes with a quantum yield close to unity were designed and photoelectrochemically characterized. Hematite, ?-Fe2O3, nanorods were synthesized and characterized for the aim of water oxidation. The morphology of the hematite nanorods was found to be in favor of the traditional isotropic nanostructured electrodes. Moreover, a unique porous nitrogen doped TiO2 material, photoactive in visible light, was obtained by reactive sputtering. The nitrogen doped material has interesting photoelectrochemical properties and is also promising for related applications such as pollution degradation by photocatalysis. Polycrystalline indium nitride, InN, was produced by reactive sputtering. Electrodes of the as prepared InN as well as electrodes annealed in nitrogen were studied for the aim of photooxidation of water.The electrodes studied are interesting candidates as potential watersplitting electrodes in photoelectrochemical cells, even if all had in common that further improvements and optimizations need to be done.