Fig. 4: Elemental composition and oxidation state of the electrode before and after PEC test.

XPS survey spectra (a) and high-resolution XPS spectra of Os 4 f (b), F 1 s (c), C 1 s (d), N 1 s (e) and O 1 s (f) for Si/TiO₂/przpOs and Si/TiO₂/trzpOs before and after PEC measurements.