Fig. 5: AP-XPS measurements and DFT modeling of the reaction pathway.
From: Surface-reaction induced structural oscillations in the subsurface
a Photoelectron spectra of O 1s obtained from the CuO surface by oxidizing Cu at pO2 ≈ 133 Pa and T = 350 °C (upper panel) and its subsequent exposure to 0.53 Pa of the constant flow of hydrogen gas at 300 °C (lower panel). The hydrogen exposure induces the broadening of the O 1s spectrum to the higher binding energy side, where the major peak corresponds to lattice oxygen in CuO (red) and the shoulder is ascribed to the presence of surface hydroxyl groups (blue). b A H2 molecule placed above the lattice O at the CuO\((\bar 220)\) surface, c DFT-relaxed structure showing the spontaneous dissociation of the H2 molecule into two atomic H atoms that form two OH groups by bonding to adjacent lattice O. Blue, red, and pink balls represent Cu, O and H, respectively.
