Synergy of Cd Doping and S Vacancies in Cd x Zn 1- x In 2 S 4 Hierarchical Nanotubes for Highly Improved Visible-Light-Driven H 2 Evolution.

Photocatalytic water splitting over semiconductors is believed as a promising avenue to obtain H 2 fuel from renewable solar energy. However, developing highly active and non-noble-metal photocatalysts for H 2 evolution is still quite challenging to date. In this work, by constructing nanosheet-based nanotubes with Cd-doping and S vacancies, a highly improved visible-light-driven H 2 production for ZnIn 2 S 4 is achieved. Unlike nanoflowers aggregated with nanosheets, the nanosheet-assembled hierarchical nanotubes allow multiple scattering and reflection of incident light within the interior space, leading to an enhanced light-harvesting efficiency. Together with the benefits from Cd doping and S-vacancy engineering, including narrowed band gaps, efficient transmission and separation of charge carriers, abundant catalytically active sites, heightened photo-stability and photo-electron reduction capacity, as well as a strong electrostatic attraction to protons, the synthesized S-deficient Cd x Zn 1- x In 2 S 4 hierarchical nanotubes exhibit an extraordinary photocatalytic H 2 evolution capability under visible-light irradiation, delivering an outstanding H 2 -generation activity of 28.99 mmol·g -1 ·h -1 (corresponding to an apparent quantum yield of 37.1% at 400 nm), which is much superior to that of Cd x Zn 1- x In 2 S 4 nanoflowers, Pt-loaded ZnIn 2 S 4 nanotubes, and most ever reported ZnIn 2 S 4 -based photocatalysts. Our study could inspire the development of low-cost and high-performance photocatalysts via rational structural design and optimization.