We employ aberration-corrected scanning transmission electron microscopy (STEM) to study the cross-sectional structure of the photoanode on its atomic scale by taking the as-fabricated n-Si/SiO x /TiO x /2 nm NiFe oxyhydroxides-alloy photoanode as a representative (Fig. ). The high-resolution STEM image in Fig. presents the layered structure of the photoanode, reporting the top NiFe alloy layer with a thickness of 2.47 ± 0.24 nm and the intersectional amorphous TiO x /SiO x layer with a thickness of 1.62 ± 0.26 nm (measurement results summarized in Fig. ). The scattered lattice fringes in the top layer confirm the existence of nanocrystalline grains with different orientations. The interface between NiFe alloy film and the amorphous TiO x /SiO x layer exhibits rough features corresponding to the curved structures in the plan-view TEM image (Fig. ).