(Invited) Photoelectrocatalysis: Solar-Assisted Hydrogen Production in Microgravity Environments

Wednesday, 31 May 2017: 14:00
Churchill C2 (Hilton New Orleans Riverside)
K. Brinkert (European Space Agency, ESTEC), M. H. Richter (California Institute of Technology), J. Liedtke (European Space Agency, ESTEC), S. Mitrovic (California Institute of Technology), Ö. Akay (Helmholtz Center Berlin), M. Giersig (Freie University Berlin), H. Matsushima (Hokkaido University), Y. Fukunaka (Nanotechnology Research Institute, Waseda), and H. J. Lewerenz (California Institute of Technology)
Artificial photosynthesis systems, which follow the concept of the Z-scheme of natural photosynthesis, are presently being realized as catalyst-functionalized photovoltaic tandem devices for the photoelectrochemical oxidation of water and the simultaneous generation of hydrogen as a so-called “solar fuel”. The successful implementation of an efficient photoelectrochemical (PEC) water splitting cell is not only a highly desirable approach to solving the energy challenge on earth: an effective air revitalization system generating a constant flux of O2 while simultaneously recycling CO2 and providing a sustainable fuel supply is also essential for the International Space Station and long-term space missions, where a regular resupply from earth is not possible.

Here, we present the photoelectrochemical production of hydrogen in microgravity environments on p-type indium phosphide electrodes with deposited rhodium electrocatalysts. Our findings indicate that microgravity has a significant impact on the gas bubble evolution behaviour and the mass transfer rate of the evolved hydrogen gas on the electrode surface. Furthermore, microgravity influences the current-voltage characteristics and the overall solar-to-hydrogen efficiency of the catalyst functionalized semiconductor-based half-cell. Further experiments with nanostructured rhodium catalysts fabricated by shadow nanosphere lithography on the InP surface suggest that the structure of the electrode surface plays a significant role for the gas bubble evolution behaviour and for the further the development of efficient prototypes for solar-assisted water splitting and hydrogen production that operate in micro- and hypergravity environments.