The O-O Bonding and Hydrogen Storage in the Pyrite-type PtO₂

We have synthesized pyrite-type PtO₂ (py-PtO₂) at 50-60 GPa and successfully recovered it at 1 bar. The observed O-O stretching vibration in Raman spectra provides direct evidence for inter-oxygen bonding in the structure. We also identified the O-H vibrations in py-PtO₂ synthesized from the lowerature areas, indicating hydrogenation, py-PtO₂H_x (x ≤ 1). Diffraction patterns are consistent with a range of degrees of hydrogenation controlled by temperature. We found that py-PtO₂ has a high bulk modulus, 314 ± 4 GPa. The chemical behaviors found in py-PtO₂ have implications for the hydrogen storage in materials with anion-anion bonding, and the geochemistry of oxygen, hydrogen, and transition metals in the deep planetary interiors.