Bi₂O₃ - Bismuth (III) Oxide

Bismuth oxide has a number of stable polymorphs but investigations into photocatalytic properties focus upon the semiconducting monoclinic form which is stable at room temperature. Other phases, such the high O^2- conductivity δ-Bi₂O₃, may be stabilised through doping or quenched from high temperature synthesis.

Figure 1: Crystal structure of monoclinic Bi2O3

In the bulk, pure bismuth oxide has a direct band gap of 2.6 eV. As a metal oxide it shows fair chemical stability over medium time scales although the formation of bismutite (Bi₂O₃.CO₂) has been observed over a time scale of 6 months (Levin and Roth, J Res Nat Bur Stand, 68A(2) 189 (1964)). Bi₂O₃ has been demonstrated to be an active photocatalyst for the watersplitting reaction (Gurunathan, Int. J. Hydrogen Energy, 29 933 (2004)).