  We show that oxidation of phosphorene can lead to the formation of a new
family of planar (2D) and tubular (1D) oxides and sub-oxides, most of them
insulating. This confers to black phosphorus a native oxide that can be used as
barrier material and protective layer. Further, the bandgap of phosphorene
oxides depends on the oxygen concentration, suggesting that controlled
oxidation can be used as a means to engineer the bandgap. For the oxygen
saturated composition, P$_2$O$_5$, both the planar and tubular phases have a
large bandgap energy of about 8.5eV, and are transparent in the near UV. These
two forms of phosphorene oxides are predicted to have the same formation
enthalpy as o$^\prime$-P$_2$O$_5$, the most stable of the previously known
forms of phosphorus pentoxide.
