Improved photoelectrochemical properties of TiO₂ nanotubes doped with Er and effects on hydrogen production from water splitting

Erbium-doped TiO₂ nanotubes (Er–TiO₂ 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–TiO₂ NTs have crystal sizes of about 24–30 nm, smaller than those of pure TiO₂ NTs, and contain only the anatase phase. Er–TiO₂ 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⁻² at a bias potential of 1.5 V vs. Hg/HgO) compare to pure TiO₂ NTs. The photocatalytic activity of the Er–TiO₂ NTs are evaluated in a hydrogen generation reaction, and the results show hydrogen production of ∼17.39 μmolhr⁻¹cm⁻². Further experiments demonstrate that Er–TiO₂ 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.