title: Noble-Metal-Free Photocatalytic H2Generation: Active and Inactive 'Black' TiO2Nanotubes and Synergistic Effects.
abstract: Over the past five years a number of different synthesis approaches has been reported to obtain so-called 'black' titania. One of the outstanding features of the material is that certain synthesis processes lead to the formation of an intrinsic co-catalytic center and thus enable noble-metal free photocatalytic H2-generation. In the present work, using TiO2nanotube layers, we compare three common 'blackening' approaches, namely i) the original high-pressure hydrogenation (HPT-H2), ii) a classic high temperature reduction in Ar, and iii) an electrochemical (cathodic) reduction. We demonstrate that except for high pressure hydrogenation also cathodic reduction leads to an activation of TiO2- that is, it exhibits noble-metal-free photocatalytic H2generation. Moreover, we show that a combination of cathodic reduction/high pressure hydrogenation leads to a synergistic effect, that is, a significant enhancement of the combined co-catalytic activity.
authors.affiliation: Department of Materials Science WW-4, LKO, University of Erlangen-Nuremberg, Martensstrasse 7, 91058, Erlangen, Germany.
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.affiliation: Department of Materials Science WW-4, LKO, University of Erlangen-Nuremberg, Martensstrasse 7, 91058, Erlangen, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Schneider
authors.affiliation: High Pressure Laboratory, Chair of Separation Science and Technology, University of Erlangen-Nuernberg, Haberstrasse 11, 91058, Erlangen, Germany.
authors.forename: Detlef
authors.initials: D
authors.lastname: Freitag
authors.affiliation: Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander-University (FAU), Egerlandstrasse 1, 91058, Erlangen, Germany.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Zolnhofer
authors.affiliation: Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander-University (FAU), Egerlandstrasse 1, 91058, Erlangen, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Meyer
authors.affiliation: Department of Materials Science WW-4, LKO, University of Erlangen-Nuremberg, Martensstrasse 7, 91058, Erlangen, Germany. schmuki@ww.uni-erlangen.de.|Department of Chemistry, King Abdulaziz University, Jeddah, Saudi Arabia.. schmuki@ww.uni-erlangen.de.
authors.forename: Patrik
authors.initials: P
authors.lastname: Schmuki
keywords: black TiO2; nanotubes; noble metal free; photocatalytic H2 evolution; synergistic effects