Improved photoelectrochemical properties of TiO nanotubes doped with Er and effects on hydrogen production from water splitting.

Erbium-doped TiO nanotubes (Er-TiO NTs) are prepared with a combination of anodization and electrochemical deposition using various proportions of erbium and adjusting the time of the process. The surface characterization techniques and electrochemical analysis are applied to study the physicochemical and photoelectrochemical (PEC) properties of the as-prepared photocatalysts. Er-TiO NTs have crystal sizes of about 24-30 nm, smaller than those of pure TiO NTs, and contain only the anatase phase. Er-TiO NTs exhibit an effective photo-conversion efficiency (PCE) of 1.58% and a photosensitivity of 115.06. The modified sample are also more efficient (photocurrent density of 6.64 mAcm at a bias potential of 1.5 V vs. Hg/HgO) compare to pure TiO NTs. The photocatalytic activity of the Er-TiO NTs are evaluated in a hydrogen generation reaction, and the results show hydrogen production of ∼17.39 μmolhrcm. Further experiments demonstrate that Er-TiO NTs successfully degrade methylene blue, with the most active sample reaching 85% photocatalysis after 180 min. This study shows that doping conditions significantly affect the optical and electrical properties of the resulting material, and that the current electrochemical approach to metal doping can be used for efficient and stable PEC water splitting.