TY  - JOUR
AU  - Ronge, Emanuel
AU  - Cottre, Thorsten
AU  - Welter, Katharina
AU  - Smirnov, Vladimir
AU  - Ottinger, Natalie Jacqueline
AU  - Finger, Friedhelm
AU  - Kaiser, Bernhard
AU  - Jaegermann, Wolfram
AU  - Jooss, Christian
TI  - Stability and Degradation Mechanism of Si-based Photocathodes for Water Splitting with Ultrathin TiO2 Protection Layer
JO  - Zeitschrift für physikalische Chemie
VL  - 234
IS  - 6
SN  - 2196-7156
CY  - Berlin
PB  - ˜Deœ Gruyter
M1  - FZJ-2020-02476
SP  - 1171–1184
PY  - 2020
AB  - Using transmission and scanning electron microscopy, we study mechanisms which determine the stability of Silicon photocathodes for solar driven water splitting. Such tandem or triple devices can show a promising stability as photocathodes if the semiconductor surface is protected by an ultrathin TiO2 protection layer. Using atomic layer deposition (ALD) with Cl-precursors, 4–7 nm thick TiO2 layers can be grown with high structural perfection. The layer can be electrochemically covered by Pt nanoparticels serving as electro-catalysts. However, Cl-remnants which are typically present in such layers due to incomplete oxidation, are the origin of an electrochemical degradation process. After 1 h AM1.5G illumination in alkaline media, circular shaped corrosion craters appear in the topmost Si layer, although the TiO2 layer is intact in most parts of the crater. The crater development is stopped at local inhomogenities with a higher Pt coverage. The observations suggests that reduced Titanium species due to Cl−/O2− substitution are nucleation sites of the initial corrosion steps due to enhanced solubility of reduced Ti in the electrolyte. This process is followed by electrochemical dissolution of Si, after direct contact between the electrolyte and the top Si layer surface. To increase the stability of TiO2 protected photocathodes, formation of reduced Ti species must be avoided.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000542554000007
DO  - DOI:10.1515/zpch-2019-1481
UR  - https://juser.fz-juelich.de/record/877852
ER  -