SrTaO2N

SrTaO2N is a mixed-anion oxide–nitride compound belonging to the family of perovskite oxynitrides. Its formula is often written SrTa(O,N)3, reflecting the partial substitution of oxide by nitride in the ABO3 lattice. It is of interest as a visible-light–active photocatalyst for water splitting.

In the crystal structure, SrTaO2N adopts a perovskite-derived framework in which Ta occupies the B site and is coordinated by an octahedral array of oxygen and nitrogen. The A-site is occupied by Sr2+. The anion sublattice contains both oxide and nitride, typically with a certain degree of disorder or short-range ordering, which influences the electronic structure and band gap.

SrTaO2N is usually synthesized by ammonolysis or nitridation of oxide precursors such as SrTaO3 or SrTaO4 at high temperature in flowing ammonia or another nitrogen source. Conditions commonly range from about 800 to 1100°C, with treatment times that promote partial replacement of O2- by N3- to form the oxynitride.

Optically, SrTaO2N has a band gap in the range of roughly 2.0 to 2.5 eV, enabling absorption in the visible region. Its valence band is derived mainly from O 2p and N 2p orbitals, and the conduction band from Ta 5d. These properties make SrTaO2N a candidate photocatalyst for water splitting under visible light, often used with sacrificial electron donors or paired with co-catalysts such as platinum to achieve hydrogen evolution, and in some cases explored for overall water splitting in composite systems.

Ongoing research addresses improving stability, charge separation, and anion ordering, as well as integration into heterojunctions and cocatalyst-decorated architectures to enhance efficiency.