The surface morphology was analyzed with a Zeiss Gemini 450 SEM. High resolution X-ray photoelectron spectroscopy (XPS) spectra of the photoanodes was obtained by a Physical Electronics (PHI) Quantum 2000 X-ray photoelectron spectrometer featuring monochromatic Al-K radiation, generated from an electron beam operated at 15 kV and 35 W. The energy scale linearity of the instrument was established through calibration with a reference sample of Au. The elemental composition maps in the cross-section were obtained by transmission electron microscopy (TEM) at a Talos 200FX equipped with a SuperX (Bruker). The samples for TEM measurement were prepared by focused ion beam (FIB) at a Helios 5 UX.