Extended Data Fig. 2: LEEM observations and DFT calculations.
From: Spatiotemporal imaging of charge transfer in photocatalyst particles
a–c, LEEM image of EH-Cu2O particles recorded at 10 eV (a) and LEED patterns recorded at 30 eV for the {001} (b) and {111} (c) facets of EH-Cu2O particles circled in a. The LEED patterns and the ratio of the reciprocal lattice a* and b* (\(\frac{\surd 3}{\surd 2}\)) determine the (1×1) surface structures for {001} and {111} facets (see detailed analyses in Methods). d–i, Optimized geometries of the {001} (d–f) and {111} (g–i) surfaces of Cu2O without (d, g) and with VCu (e, h) or (H-VCu) (f, i) defects. The red, pink, and white spheres represent O, Cu, and H atoms, respectively. j, Calculated formation energies of the (H-VCu) defects on the {001} and {111} facets at the HSE06 level based on the 2×2 periodic Cu2O slab structures depicted in d–i (see details in Methods). These results indicate that the formation of (H-VCu) defects is much more favourable at {111} facets compared to {001} facets. k, Charge density difference obtained for the Cu2O {111} surface structure (i) with a (H-VCu) defect. The red, blue, and white spheres represent O, Cu, and H atoms, respectively. The yellow and cyan colours denote the increase and decrease in electron density, respectively. The obtained results demonstrate that the formation of (H-VCu) defects increases the electron density at Cu atoms. We also performed a Bader charge analysis and found that the averaged charge on Cu atom decreased from 0.514 to 0.495 after the formation of (H-VCu) defects. Therefore, the presence of (H-VCu) lowers the valences of the surrounding Cu atoms.
