Double-Side Co-Catalytic Activation of Anodic TiO2 Nanotube Membranes with Sputter-Coated Pt for Photocatalytic H2 Generation from Water/Methanol Mixtures.

Self-standing TiO2 nanotube layers in the form of membranes are fabricated by self-organizing anodization of Ti metal and a potential shock technique. The membranes are then decorated by sputtering different Pt amounts i) only at the top, ii) only at the bottom or iii) at both top and bottom of the tube layers. The Pt-decorated membranes are transferred either in tube top-up or in tube top-down configuration onto FTO slides and are investigated, after crystallization, as photocatalysts for H2 generation using either front or back-side light irradiation. Double-side Pt-decoration of the tube membranes leads to higher H2 generation rates (independently of tube and light-irradiation configuration) compared to membranes decorated at only one side with similar overall Pt amounts. The results suggest that this effect cannot be only ascribed to the overall amount of Pt co-catalyst as such but also to its distribution at both tube extremities. This leads to optimized light absorption and electron diffusion/transfer dynamics: the central part of the membranes acts as light-harvesting zone and electrons therein generated can diffuse towards the Pt/TiO2 active zones (tube extremities) where they can react with the environment and generate H2 .