Erwin Reisner, University of Cambridge, UK, and colleagues have built lightweight artificial leaves that convert CO₂ and water into H₂ or syngas using sunlight. The modules consist of a base of indium tin oxide-coated polyethylene terephthalate. On top of this are two light-absorbing photoelectrodes made of perovskite and bismuth vanadium oxide (BiVO₄) combined with organic semiconductors. This structure is complemented by catalysts and a layer of carbon nanotubes. Depending on the catalyst, water and CO₂ are split to produce mainly hydrogen or syngas.

The researchers tested the first modules on a river in Cambridge. They produced about 70.2 µmol H₂ g⁻¹h⁻¹, or 4.88 µmol CO and 2.11 µmol H₂ for the syngas version. These values correspond to a solar-to-fuel efficiency of 0.58 % for hydrogen and 0.053 % for syngas. The self-sufficient modules are thus expected to be as efficient as a real plant leaf.

The scientists demonstrated the potential for scalability using 100 cm² artificial leaves. These showed comparable performance and stability. Bubbles that formed during operation allowed the devices to float.

The researchers suggest that these thin, flexible miniature reactors could be used as floating hydrogen or syngas factories on lakes, in harbors, or even at sea. The modules still need further optimization.

• Floating perovskite-BiVO₄ devices for scalable solar fuel production,
  Virgil Andrei, Geani M. Ucoski, Chanon Pornrungroj, Chawit Uswachoke, Qian Wang, Demetra S. Achilleos, Hatice Kasap, Katarzyna P. Sokol, Robert A. Jagt, Haijiao Lu, Takashi Lawson, Andreas Wagner, Sebastian D. Pike, Dominic S. Wright, Robert L. Z. Hoye, Judith L. MacManus-Driscoll, Hannah J. Joyce, Richard H. Friend, Erwin Reisner,
  Nature 2022, 608, 518–522.
  https://doi.org/10.1038/s41586-022-04978-6