Boosted photocatalytic hydrogen evolution by tuning inner pore size and co-catalyst thickness of the anodic TiO2 nanotubes

Abstract

The formation of well aligned TiO2 nanotubes with suitable inner diameters is a pre-requisite for photocatalytic application. The inner diameters can be tuned by the composition of electrolyte, anodization temperature, and applied potential. Here, we have successfully formed the TiO2 nanotubes with wide inner diameters by controlling the anodization potential of the Ti metal substrate. The anodizations were performed in the aqueous solution of ethylene glycol mixed with hydrofluoric acid as an electrolyte at potentials of 150-240 V at 40 degrees C. It resulted into TiO2 nanotubes with inner diameters in the range of 160-400 nm and lengths about 6-8 mu m, respectively. Moreover, the TiO2 nanotubes were sputter coated with thin layers (1-5 nm) of Pt and Au nano-particles. Finally, we compared the photocatalytic behavior of the as-prepared TiO2 nanotubes and those coated with Au and Pt nanoparticles. Interestingly, 1 nm Pt coated 300 and 400 nm inner diameter TiO2 nanotubes showed highest H-2 production rate of 25 mu L h(-1) cm(-2) under a 10 h of light illumination.