Evidence for an Ag4O3 Phase of Silver Oxide

Article abstract of DOI:10.1021/j100365a093

The structure of chemically and electrochemically prepared AgO materials was investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy.It was found that chemically prepared (CP) AgO is composed of Ag(+) and Ag(3+) ions coordinated with two oxygens at 2.13 Angstroem and four oxygens at 1.99 Angstroem, respectively.For electrochemically prepared (EP) AgO, the Ag(+) ions are also coordinated with two oxygens at a distance of 2.13 Angstroem.However, the coordination number for the Ag(3+) ions varies from 2.8 to 3.5 oxygens without any significant change in the coordination distance of 1.99 Angstroem.That is, EP AgO is really AgO1-δ, where δ is the degree of oxygen deficiency near the Ag(3+) ions.The magnitude of δ can be as large as 0.29 +/- 0.05 and is a strong function of preparation procedures.The EXAFS results reveal that a phase of silver oxide, Ag4O3, is formed electrochemically.The EXAFS results also suggest that the electrochemical oxidation of Ag or Ag2O to AgO proceeds via the formation of Ag4O3 as an intermediate step.