A novel composite of TiO2 nanotubes with remarkably high efficiency for hydrogen production in solar-driven water splitting

Abstract

As one of the most promising photocatalysts, TiO₂ 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/TiO₂/carbon nanotube (CTCNT) composite featuring a TiO₂ nanotube sandwiched between two thin tubes of carbon with graphitic characteristics. The carbon layer is only about 1 nm thick covering the surface of TiO₂ 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 super-high solar-driven hydrogen production rate (37.6 mmol h⁻¹ g⁻¹), which is much greater than the best yields ever reported for TiO₂-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.