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Revealing Nanoscale Chemical Heterogeneities in Polycrystalline Mo‐BiVO 4 Thin Films
Author(s) -
Eichhorn Johanna,
ReyesLillo Sebastian E.,
Roychoudhury Subhayan,
Sallis Shawn,
Weis Johannes,
Larson David M.,
Cooper Jason K.,
Sharp Ian D.,
Prendergast David,
Toma Francesca M.
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202001600
Subject(s) - crystallite , grain boundary , materials science , x ray photoelectron spectroscopy , nanoscopic scale , thin film , absorption spectroscopy , spectral line , absorption (acoustics) , chemical physics , crystallography , mineralogy , microstructure , nanotechnology , chemical engineering , optics , composite material , chemistry , metallurgy , physics , astronomy , engineering
The activity of polycrystalline thin film photoelectrodes is impacted by local variations of the material properties due to the exposure of different crystal facets and the presence of grain/domain boundaries. Here a multi‐modal approach is applied to correlate nanoscale heterogeneities in chemical composition and electronic structure with nanoscale morphology in polycrystalline Mo‐BiVO 4 . By using scanning transmission X‐ray microscopy, the characteristic structure of polycrystalline film is used to disentangle the different X‐ray absorption spectra corresponding to grain centers and grain boundaries. Comparing both spectra reveals phase segregation of V 2 O 5 at grain boundaries of Mo‐BiVO 4 thin films, which is further supported by X‐ray photoelectron spectroscopy and many‐body density functional theory calculations. Theoretical calculations also enable to predict the X‐ray absorption spectral fingerprint of polarons in Mo‐BiVO 4 . After photo‐electrochemical operation, the degraded Mo‐BiVO 4 films show similar grain center and grain boundary spectra indicating V 2 O 5 dissolution in the course of the reaction. Overall, these findings provide valuable insights into the degradation mechanism and the impact of material heterogeneities on the material performance and stability of polycrystalline photoelectrodes.