A theoretical model for the prediction of drop and bubble &kid-particle)

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As one of the most promising photocatalysts, TiO 2 suffers from disadvantages of a wide band gap energy and especially the ultrafast recombination of photoinduced-charges, which limit its practical application for efficient solar water splitting. Here we show a hitherto unreported carbon/TiO 2 /carbon nanotube (CTCNT) composite featuring a TiO 2 nanotube sandwiched between two thin tubes of carbon with graphitic characteristics. The carbon layer is only about 1 nm thick covering the surface of TiO 2 nanotubes. The minimum bandgap between the edges of band tails for the CTCNTs can conjecturally be narrowed to 0.88 eV, and the measured apparent quantum efficiency of CTCNT in the ultraviolet light region is even close to 100%, indicating it can greatly enhance the utilization of sunlight and extremely suppress charge recombination. As a consequence, under illumination of one AM 1.5G sunlight, CTCNT can give a superhigh solar-driven hydrogen production rate (37.6 mmol h À1 g À1 ), which is much greater than the best yields ever reported for TiO 2 -based photocatalysts. We anticipate this work may open up new insights into the architectural design of nanostructured photocatalysts for effective capture and conversion of sunlight. Broader contextSolar-driven water-splitting into H 2 and O 2 is recognized as a promising clean, sustainable way to overcome the limited supply of fossil fuels and the greenhouse effect. This requires that photocatalysts effectively harvest sunlight and simultaneously drive the photoreaction with high quantum efficiency. The rational design of efficient catalysts for water splitting is one of the major challenges in recent years. In this work, we show a hitherto unreported carbon/TiO 2 /carbon nanotube structure (CTCNT) that features in a TiO 2 nanotube sandwiched between two thin tubes of graphitic carbon. This unique construction endows the CTCNT material with a minimum bandgap narrowing to 0.88 eV and an excellent apparent quantum efficiency of nearly 100% in the ultraviolet light region. As the result, a super-high solar-driven hydrogen production rate (37.6 mmol h À1 g À1 ) can be given by the CTCNT material, indicating it can greatly enhance the utilization of sunlight and extremely suppress the charge recombination. We anticipate this work may open up new insights to improve the photocatalytic conversion efficiency in solar-driven reactions.

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