  In the present work we show, how a high pressure hydrogenation of commercial
anatase or anatase/rutile powder can create a photocatalyst for hydrogen
evolution that is highly effective and stable without the need of any
additional co-catalyst. This activation effect can not be observed for rutile.
For anatase/rutile mixtures, however, a strong synergistic effect is found
(similar to findings commonly observed for noble metal decorated TiO2). ESR
measurements indicate the intrinsic co-catalytic activation of anatase TiO2 to
be due to specific defect centers formed during hydrogenation.
