Direct Z-scheme anatase/rutile bi-phase nanocomposite TiO2 nanofiber photocatalyst with enhanced photocatalytic H2-production activity

Design and preparation of direct Z-scheme anatase/rutile TiO2 nanofiber photocatalyst to enhance photocatalytic H2-production activity via water splitting is of great importance from both theoretical and practical viewpoints. Herein, we develop a facile method for preparing anatase and rutile bi-phase TiO2 nanofibers with changing rutile content via a slow and rapid cooling of calcined electrospun TiO2 nanofibers. The phase structure and composition, surface morphology, specific surface area, surface chemical composition and element chemical states of TiO2 nanofibers were analyzed by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), nitrogen adsorption and X-ray photoelectron spectroscopy (XPS). By a rapid cooling of 500 °C-calcined electrospun TiO2 precursor, anatase/rutile bi-phase TiO2 nanofibers with a roughly equal weight ratio of 55 wt.% anatase and 45 wt.% rutile were prepared. The enhanced H2 production performance was observed in the above obtained anatase/rutile composite TiO2 nanofibers. A Z-scheme photocatalytic mechanism is first proposed to explain the enhanced photocatalytic H2-production activity of anatase/rutile bi-phase TiO2 nanofibers, which is different from the traditional heterojunction electron–hole separation mechanism. This report highlights the importance of phase structure and composition on optimizing photocatalytic activity of TiO2-based material.