Understanding bulk and interfacial properties of ternary metal oxide photoanodes for water splitting
Event details
| Date | 16.02.2018 |
| Hour | 12:15 › 13:15 |
| Speaker |
Prof. Roel van de Krol, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Institute for Solar Fuels, Berlin, Germany. Bio : Roel van de Krol (1971) is director of the Insitute for Solar Fuels at the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) and professor at the Chemistry Department of TU Berlin. After earning his PhD from TU Delft in 2000 and a postdoctoral stay at MIT (USA), he returned to TU Delft where he was an assistant professor until he moved to HZB in 2012. His research focuses on the development of materials and devices for the photoelectrochemical conversion of sunlight to chemical fuels. One of the specialties of his group is the work on multinary metal oxides for application as semiconducting photoelectrodes. Understanding how surface and bulk defects affect light absorption, charge transport, recombination, and catalytic activity in these materials is at the heart of these efforts. |
| Location | |
| Category | Conferences - Seminars |
Abstract : The direct photo-electrochemical conversion of water and CO2 into chemical fuels represents an exciting new pathway for the combined conversion and storage of solar energy. One of the main challenges in this field is to find semiconducting light absorbers that are efficient, chemically stable, and easy to synthesize. I will show some recent progress on BiVO4, a promising photoanode material with a bandgap of 2.4 eV. We have investigated the carrier dynamics of undoped and doped BiVO4 with ultrafast time-resolved spectroscopy, and found that carrier trapping at defects and the formation of polarons play an important role. Hydrogen was found to be a particularly effective dopant, since it simultaneously passivates bulk defect states and increases the dark conductivity [1]. Once the carriers have made it to the interface, the challenge is to prevent surface recombination [2]. Using ambient pressure photoemission techniques, we now have some first clues about the chemical nature of BiVO4 surface states and a better insight in how the solid/liquid interface behaves under illumination [3]. These initial results are the first steps towards a molecular-level understanding of the BiVO4/electrolyte interface that may eventually help to design efficient solar fuel generators. Ultimately, however, we need to find semiconductors with smaller bandgaps. I will show some of our efforts on CuBi2O4, a promising new photocathode material with a bandgap of about 1.7 eV [4]. Finally, some recent results on the growth of ultrathin TiO2 protection layers by atomic layer deposition will be discussed. In-line XPS allows us to monitor how the chemistry of these films evolves during growth, and offers useful guidelines on how to minimize the presence of impurities from the precursor ligands. In addition, it has provided us with several clues on the chemical nature of the defects that enable the conductivity of holes in ‘leaky’ TiO2.
References
[1] J.W. Jang et al., Adv. Energy Mater. 1701536 (2017)
[2] C. Zachäus et al., Chem. Sci. 8, 3712 (2017)
[3] M. Favaro et al., J. Phys. Chem. B 122, 801 (2018)
[4] F. Wang et al., J. Am. Chem. Soc. 139, 15094 (2017)
References
[1] J.W. Jang et al., Adv. Energy Mater. 1701536 (2017)
[2] C. Zachäus et al., Chem. Sci. 8, 3712 (2017)
[3] M. Favaro et al., J. Phys. Chem. B 122, 801 (2018)
[4] F. Wang et al., J. Am. Chem. Soc. 139, 15094 (2017)
Practical information
- General public
- Free
Organizer
- Prof. Sophia Haussener https://lrese.epfl.ch/
Contact
- Sophia Haussener