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SUMMARY:Understanding bulk and interfacial properties of ternary metal oxi
 de photoanodes for water splitting
DTSTART:20180216T121500
DTEND:20180216T131500
DTSTAMP:20260527T073107Z
UID:5b184541a33f1ef1469a2236f909ef9f69c6078918cb270ecea15f83
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Roel van de Krol\, Helmholtz-Zentrum Berlin für Materia
 lien und Energie GmbH \, Institute for Solar Fuels\, Berlin\, Germany.   
                                        
     \nBio : Roel van de Krol (1971) is director of the Insitute for So
 lar Fuels at the Helmholtz-Zentrum Berlin für Materialien und Energie (HZ
 B) and professor at the Chemistry Department of TU Berlin. After earning h
 is PhD from TU Delft in 2000 and a postdoctoral stay at MIT (USA)\, he ret
 urned to TU Delft where he was an assistant professor until he moved to HZ
 B in 2012. His research focuses on the development of materials and device
 s for the photoelectrochemical conversion of sunlight to chemical fuels. O
 ne of the specialties of his group is the work on multinary metal oxides f
 or application as semiconducting photoelectrodes. Understanding how surfac
 e and bulk defects affect light absorption\, charge transport\, recombinat
 ion\, and catalytic activity in these materials is at the heart of these e
 fforts.\nAbstract : The direct photo-electrochemical conversion of water a
 nd CO2 into chemical fuels represents an exciting new pathway for the comb
 ined 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 progr
 ess on BiVO4\, a promising photoanode material with a bandgap of 2.4 eV. W
 e have investigated the carrier dynamics of undoped and doped BiVO4 with u
 ltrafast time-resolved spectroscopy\, and found that carrier trapping at d
 efects and the formation of polarons play an important role. Hydrogen was 
 found to be a particularly effective dopant\, since it simultaneously pass
 ivates bulk defect states and increases the dark conductivity [1]. Once th
 e carriers have made it to the interface\, the challenge is to prevent sur
 face recombination [2]. Using ambient pressure photoemission techniques\, 
 we now have some first clues about the chemical nature of BiVO4 surface st
 ates and a better insight in how the solid/liquid interface behaves under 
 illumination [3]. These initial results are the first steps towards a mole
 cular-level understanding of the BiVO4/electrolyte interface that may even
 tually help to design efficient solar fuel generators. Ultimately\, howeve
 r\, 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 o
 f ultrathin TiO2 protection layers by atomic layer deposition will be disc
 ussed. In-line XPS allows us to monitor how the chemistry of these films e
 volves during growth\, and offers useful guidelines on how to minimize the
  presence of impurities from the precursor ligands. In addition\, it has p
 rovided us with several clues on the chemical nature of the defects that e
 nable the conductivity of holes in ‘leaky’ TiO2.\nReferences\n[1] J.W.
  Jang et al.\, Adv. Energy Mater. 1701536 (2017)\n[2] C. Zachäus et al.\,
  Chem. Sci. 8\, 3712 (2017)\n[3] M. Favaro et al.\, J. Phys. Chem. B 122\,
  801 (2018)\n[4] F. Wang et al.\, J. Am. Chem. Soc. 139\, 15094 (2017)\n 
LOCATION:MED 2 1522 https://plan.epfl.ch/?room=MED21522
STATUS:CONFIRMED
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