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H2 and O2 photocatalytic production on TiO2 nanotube arrays: Effect of the anodization time on structural features and photoactivity

Paper ID Volume ID Publish Year Pages File Format Full-Text
46313 46437 2013 8 PDF Available
Title
H2 and O2 photocatalytic production on TiO2 nanotube arrays: Effect of the anodization time on structural features and photoactivity
Abstract

TiO2 nanotube (NT) arrays of different lengths were prepared by electrochemical anodization of ca. 10 cm2 area titanium disks in NH4F–H2O–formamide solution for different times, followed by annealing at 450 °C. After Pt deposition on the opposite side of the disk, the so obtained Ti-supported crystalline anodic oxides were employed as photoactive electrodes in a two compartments cell for separate H2 and O2 production through water photosplitting and characterized by SEM, XRD analysis and photocurrent measurements. The anodization time affected the phase composition and morphology of the growing NTs, which strictly influenced their photocatalytic activity. Short anodization times (40–60 min) resulted in well aligned short tubes composed of anatase-rutile mixed phases. Longer anodization (>2.5 h) yielded thicker NT arrays covered on top by a preferentially oriented anatase layer that limited their photoactivity. Photocurrent intensity measurements perfectly paralleled the water splitting activity results obtained with the different NT arrays. In particular, a square-shaped fast photoresponse was recorded with ordered and fully top-open nanotubular structures. On the other hand, clogged tubes not only yielded low current densities, but also showed delayed photocurrent transient signals due to the reduced mobility of the charge carriers within the preferentially oriented anatase layer. NT arrays obtained under optimized conditions had a ca. 80:20 anatase:rutile composition and ensured a hydrogen production rate of 83 mmol h−1 m−2 (i.e. 1.9 NL h−1 m−2) in the absence of any hole scavenger or external bias.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► TiO2 nanotube arrays were grown on titanium disks by different anodization times. ► Photoelectrodes were so prepared for separate H2 and O2 production from water. ► Short anodization led to best performing aligned 80–20 anatase-rutile nanotubes. ► Long anodization produced a detrimental anatase layer covering the nanotubes top. ► Photocatalytic water splitting was perfectly mirrored by photocurrent measurements.

Keywords
Photocatalytic water splitting; H2 production; TiO2 nanotubes; Photocurrent; Photoelectrodes
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H2 and O2 photocatalytic production on TiO2 nanotube arrays: Effect of the anodization time on structural features and photoactivity
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 136–137, 5 June 2013, Pages 81–88
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us