Date published:

Ultrafast studies of hydrogen production

The studies of system for hydrogen production using the ultrafast laser spectroscopy have been presented during the International Online Conference on Hybrid and Organic Photovoltaics (HOPV21), which was held from 25 to 28 May 2021. The title of the oral presentation was: "Alternative explanation of photocurrents in dye-sensitized water splitting cells based on ultrafast laser spectroscopy results", and the authors were: Iwona Grądzka-Kurzaj, Mateusz Gierszewski, and Marcin Ziółek as presenting author.

Hydrogen can be a very efficient and ecological fuel, and its combustion only results in water. Hydrogen production is possible thanks to the reverse process, the so-called water splitting. The water splitting may occur under the influence of the application of an electric current, but it may also occur in appropriate systems under the influence of light. In this situation, we get fuel directly from solar energy, similar to the photosynthesis process in plants. Systems that can split water and produce hydrogen in this way are called photoelectrochemical cells.

Photoelectrochemical cells with molecular dyes  are one of the interesting ways to realize the water splitting under light. Recently, significant developments have been made using as dyes ruthenium complex: as so-called sensitizer and catalyst, jointly deposited on the titanium oxide. In our group, we tested such systems using techniques with very short laser pulses. The results of our research were presented as an oral presentation at the HOPV21 online conference.

The system with sensitizer and catalyst initially performed twice as well as the sensitizer and catalyst only setups (see attached diagram). We explained this effect by the very fast transfer of electrons from the catalyst to the sensitizer and from sensitizer to titanium oxide. Our results explain why systems based on ruthenium complexes on titanium oxide can serve as efficient water separation systems.