Prof. Thomas Hannappel
Group of Fundamentals for Energy Materials
Phone: +49 3677 69-2566
This project aims to understand the fundamental processes that control the electron dynamics and energetics of prototypical photoelectrode surfaces, the associated internal interfaces to semiconductor surfaces and related model systems with respect to photoelectrochemical hydrogen production. The detailed mechanisms of interface-specific electron transfer processes and their dynamics are still poorly understood. We propose to selectively modify the electronic and chemical surface properties of III-V compound semiconductor absorber systems to promote multi-electron processes. Time-resolved two-photon photoemission (tr-2PPE) for explicit surface-sensitive analysis will be combined with numerical simulations based on density functional theory (DFT) to gain a fundamental understanding of the main electron transfer and recombination processes. Tr-2PPE is a unique technique that directly studies the kinetic energy and dynamics of photoemitting electrons while accessing the electronic structure and temporal occupation of near-surface states. III-V compound semiconductors serve as relevant model systems for the investigation of interfacial dynamics with respect to selected surface modification processes. Possibilities for the modification of III-V surfaces include epitaxial growth of thin films, in-situ surface transformation and catalyst deposition. These methods can be used to produce quasi-two-dimensional coatings to slow down corrosion and increase photocatalytic activity. The modification with such surface layers allows the tuning of the electron transfer dynamics by specific electronic structural modifications. The investigation of different types of surface modifications will allow us to draw a general picture of how the design of interfaces favors the electron transport to the catalytically active surface. In the long-term perspective of the research consortium, this project will enable optimal charge separation and transfer for multi-electron catalytic processes in the planned new multilayer absorber systems.