  Noble metal cocatalysts are conventionally a crucial factor in
oxide-semiconductor-based photocatalytic hydrogen generation. In the present
work, we show that optimized high-temperature hydrogenation of commercially
available strontium titanate (SrTiO3) powder can be used to engineer an
intrinsic cocatalytic shell around nanoparticles that can create a
photocatalyst that is highly effective without the use of any additional
cocatalyst for hydrogen generation from neutral aqueous methanol solutions.
This intrinsic activation effect can also be observed for SrTiO3[100] single
crystal as well as Nb-doped SrTiO3 (100) single crystal. For all types of
SrTiO3 samples (nanopowders and either of the single crystals), hydrogenation
under optimum conditions leads to a surface-hydroxylated layer together with
lattice defects visible by transmission electron microscopy, electron
paramagnetic resonance (EPR), and photoluminescence (PL). Active samples
provide states in a defective matrix -- this is in contrast to the inactive
defects formed in other reductive atmospheres. In aqueous media, active SrTiO3
samples show a significant negative shift of the flatband potential (in
photoelectrochemical as well as in capacitance data) and a lower
charge-transfer resistance for photoexcited electrons. We therefore ascribe the
remarkable cocatalyst-free activation of the material to a synergy between
thermodynamics (altered interface energetics induced by hydroxylation) and
kinetics (charge transfer mediation by suitable Ti3+ states).
