  In the present work, a simple strategy is used to thermally oxidize TiN
nanopowder (ca. 20 nm) to an anatase phase of a TiO2:Ti3+:N compound. In
contrast to the rutile phase of such a compound this photocatalyst provides
photocatalytic activity for hydrogen evolution under AM1.5 conditions - this
without the use of any noble metal co-catalyst. Moreover the photocatalyst is
active and stable over extended periods of time (tested for 4 months).
Importantly, to achieve successful conversion to the active anatase polymorph,
sufficiently small starting particles of TiN are needed. The key factor for
catalysis is the stabilization of the co-catalytically active Ti3+ species
against oxidation by nitrogen present in the starting material.
