Fig. 1: Cobalt tetrahedra over YBC4 surface.
From: Enhanced oxygen evolution over dual corner-shared cobalt tetrahedra
a Crystal structure of YBC4 and the arrangements of corner-shared CoO4 tetrahedra in the Triangular layer and the Kagome layer. b The top view of the YBaCo4O7 (110) facet with tri-oxygen-coordinated cobalt (marked in orchid). c O 1 s core spectra from temperature-dependent XPS of an as-prepared YBC4 sample. d O K-edge EELS spectra from the sub-surface (~9 nm and ~1.5 nm) and the surface of YBC4. All spectra are aligned to Fermi energy (Ef) with 0 eV. e Extracted intensities of α peaks from sub-surface to surface. A linear background is applied to subtract the background adsorption. f A typical OH-adsorbed site, including adjacent Co from the Kagome layer and the Triangular layer, over the (110) facet. The O from adsorbed OH group is highlighted in green. g PDOS of unoccupied Co 3d states from sub-surface (dot line) and surface (dash line). The solid lines are the corresponding integrated PDOS of unoccupied Co 3d states.
