Surface dynamics of mixed silver-copper oxide AgCuO2 during X-ray photoelectron spectroscopy study

A detailed study of mixed silver-copper oxide AgCuO2 was performed using X-ray photoelectron spectroscopy. The state and ratio of elements on the surface at different probing depth was revealed using variable radiation energy. A non-uniform in-depth distribution of silver and copper states was established. Two silver states were detected on the initial surface: (1) highly oxidized Ag>1+ ions from AgCuO2 lattice and (2) impurity Ag0 metallic species. The appearance of metallic species was related to AgCuO2 surface reduction by adsorbed carbon admixtures during air-storage. It was shown that highly oxidized copper species can be identified by the analysis of shake-up satellites in Cu2p region during step-by-step exposure to X-rays. This approach, considering all spectral changes versus time, allowed us to reveal the presence of copper with the oxidation level higher than +2 on the initial AgCuO2 surface. It was found that a long-term exposure to intense X-rays significantly modifies the composition and state of the AgCuO2 surface. Possible causes of such modification are discussed in relation to the AgCuO2 reaction properties.