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Our group is interested in the development, analysis and optimization of earth-abundant, technologically advanced III-V semiconductor-Research overviewelectrocatalyst systems for the photoelectrochemical production of high-valuable chemicals and oxygen. These systems mimic the most important pieces of photosynthesis, nature's go-to solar energy conversion mechanism. Upon photoexcitation, the semiconductor transfers holes or electrons to the integrated electrocatalyst which catalyses the oxidation reaction (e.g., oxygen production) at the (photo-)anode or reduction reaction (hydrogen production, CO2 conversion into long-chain hydrocarbons etc.) at the photocathode. Of particular importance is hereby a careful energetic alignment of the semiconductor-electrocatalyst and the electrocatalyst-electrolyte interface. Furthermore, the electrocatalyst surface composition and topography plays a key role in the catalytic reaction and spectroscopic and optical techniques such as XPS and AFM, HRSEM and HRTEM, resp., are essential tools to investigate catalyst performance and establish routes for its optimization. Current projects are discussed below.

Solar fuel and oxygen production in reduced gravitational environment

Hydrogen gas bubble evolution on nanostructured p-InP/Rh photocathodes during 9.2s of free fall at the Bremen Drop Tower.

EarthA challenge for long-term space flights and the establishment of cis-lunar research platforms is the continuous supply of oxygen and fuels. We investigate light-assisted production of oxygen and fuels in reduced gravitational environments, realized at the Bremen Drop Tower, Germany, in order to provide an alternative to currently available life support systems for space travel. A particular drawback in reduced gravitational environment however is the absence of buoyancy which results in gas bubble froth layer formation in front of the electrode surface and therefore, high ohmic resistances and reduced cell-efficiencies in electrochemical reactions. We address this problem by adjusting the electrocatalyst nanotopography to form catalytic hot-spots on the electrode surface which prevents gas bubble coalescence and by investigating different electrolyte compositions. We are currently studying photoelectrochemical hydrogen and oxygen in microgravity environment and are looking to extend these studies to carbon dioxide reduction.