Researchers led by the Karlsruhe Institute of Technology have designed panel-like photoreactors based on a water-splitting photocatalyst that can produce hydrogen on rooftops or special solar farms. They argue that photoreactors have great economic potential due to their “extremely” low cost.
“Several photocatalysts are now known,” said Paul Kant from KIT’s Micro Process Engineering Institute (IMVT). “For example, they can be used to split water into hydrogen and oxygen or produce climate-neutral fuel from water and carbon dioxide.”
The proposed systems mimic the process of photosynthesis and use a photocatalyst to drive the necessary chemical reaction in electrolysis. Photoreactors contain the photocatalyst and the materials for the chemical reaction itself.
“The design method and basic structure can be applied to any sunlight-harvesting liquid, gas, or heterogeneous multiphase photocatalytic system,” the researchers stated. “However, to ensure comparability with other approaches, the design method and the resulting photoreactor have been experimentally demonstrated using a well-established, commercially available and reliable potassium iron(III) oxalate photocatalyst system.”
Photo: Karlsruhe University of Technology (KIT)
The photoreactor is manufactured hundreds of parallel reaction channels, each with a V-shaped concentrator and a tubular cavity. A V-shaped concentrator collects light from different directions and directs it into a tubular, mirrored cavity that encloses the reaction volume. “A photoreactor should ideally conduct incoming sunlight to the photocatalyst with little loss, regardless of which direction it’s coming from or where the sun is in the sky,” Kant said.
The microstructured polymer panels are coated with aluminum to ensure high reflectivity and, according to the German group, enable both optimal operating conditions and efficient light transfer to the photocatalyst throughout the day.
The researchers believe that this system configuration could lead to the production of inexpensive and efficient devices in the near future.
“The material cost of the reactor components is estimated to be $9.4 m2, as they are made from only three polymer parts, all made using established mass manufacturing techniques,” they explained. “When factoring in the $1 million per ton catalyst, the material cost estimate for the photoreactor system rises to about $22 m2.”
They presented a new concept in the study “Low-cost photoreactors for highly photon/energy-efficient solar-based synthesis”, which was published recently Joule. The research group includes researchers from the University of Toronto in Canada.
“Further optimization of the photoreactor should take into account the manufacturing of key polymer components and real-life aspects such as aging of polymers and optical coatings, as well as challenges such as dust accumulation on the rather complex surface of the photoreactor aperture,” they concluded.
