University of Tübingen develops solar cell for direct hydrogen production

A research team at the University of Tübingen, Germany has developed a solar cell that interacts with catalysts for water splitting with »remarkably high efficiency« as an integral part of a photoelectrochemical apparatus. An additional external circuit, as in conventional electrolysis powered by solar electricity (or from other electricity generation sources), is no longer required in this case (the photo shows a close-up of the photoelectrochemical solar cell in the solar simulator; the hydrogen produced can be seen in the form of gas bubbles).
This approach to solar water splitting (also known as artificial photosynthesis) »makes the technology more compact, more flexible and potentially more cost-efficient,« but also increases the demands on the solar cell. Not least among these is corrosion and the resulting threat to long-term stability. However, »we have now made great progress compared to our earlier work,« says Matthias May, head of the research group. In addition, the achieved efficiency of 18 percent (percentage of the energy from sunlight can be converted into usable hydrogen energy) is the second highest value ever measured for direct solar water splitting and, taking into account the area of the solar cell, even a new world record. In 1998, an efficiency of twelve percent was achieved for solar water splitting at the U.S. research institute NREL, followed by 14 percent in 2015 (May et al.) and 19 percent in 2018 (Cheng et al).
The Tübingen group believes the technology can be commercialized – also in view of spin-offs that have already taken place at other universities. A fundamental advantage is that, in contrast to hydrogen production with electrolysers, no high-performance connection to the power grid is required. Thus, »permanent smaller isolated applications« are possible.
The results were published in the journal Cell Reports Physical Science.
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