A Study on Doped Heterojunctions in TiO2 Nanotubes: An Efficient Photocatalyst for Solar Water Splitting

作者：Preethi L K; Antony Rajini P; Mathews Tom; Walczak Lukasz; Gopinath Chinnakonda S

来源：Scientific Reports, 2017, 7(1): 14314.

DOI：10.1038/s41598-017-14463-0

<jats:title>Abstract</jats:title><jats:p>The two important factors that affect sunlight assisted water splitting ability of TiO<jats:sub>2</jats:sub> are its charge recombination and large band gap. We report the first demonstration of nitrogen doped triphase (anatase-rutile-brookite) TiO<jats:sub>2</jats:sub> nanotubes as sun light active photocatalyst for water splitting with high quantum efficiency. Nitrogen doped triphase TiO<jats:sub>2</jats:sub> nanotubes, corresponding to different nitrogen concentrations, are synthesized electrochemically. Increase in nitrogen concentration in triphase TiO<jats:sub>2</jats:sub> nanotubes is found to induce brookite to anatase phase transformation. The variation in density of intra-band states (Ti<jats:sup>3+</jats:sup> and N 2p states) with increase in nitrogen doping are found to be critical in tuning the photocatalytic activity of TiO<jats:sub>2</jats:sub> nanotubes. The presence of bulk heterojunctions in single nanotube of different nitrogen doped TiO<jats:sub>2</jats:sub> samples is confirmed from HRTEM analysis. The most active nitrogen doped triphase TiO<jats:sub>2</jats:sub> nanotubes are found to be 12 times efficient compared to pristine triphase TiO<jats:sub>2</jats:sub>, for solar hydrogen generation. The band alignment and charge transfer pathways in nitrogen doped TiO<jats:sub>2</jats:sub> with triphase heterojunctions are delineated. Bulk heterojunctions among the three phases present in the nanotubes with intra-band defect states is shown to enhance the photocatalytic activity tremendously. Our study also confirms the theory that three phase system is efficient in photocatalysis compared to two phase system.</jats:p>

• 出版日期2017-10-30