Future long-term space travel and cis-lunar research platforms such as the Deep Space Gateway require a reliable life support system and - similarly to our demands on Earth - a renewable energy source. The production of so-called ‘solar fuels’, i.e. fuels such as hydrogen or long-chain hydrocarbons generated only from sunlight, water and carbon dioxide is currently investigated for terrestrial applications. These solar fuels are promising candidates for meeting the global quest for alternative energy sources. Currently, the most efficient systems comprise the ones operating according to the natural photosynthetic process: semiconductors are employed as light absorbers which transfer electrons upon photoexcitation to integrated electrocatalysts, catalyzing the respective half-cell reaction of water-splitting (photoanode) or fuel production (photocathode). Although, these systems are interesting as well for space applications from the point of oxygen and fuel generation, solar fuel production in microgravity environment has not been realized and investigated yet.
Our study shows that while the greatest urban challenges are in the global south, our urban scholarship is dominated by the research on and by the global north.