Conformal deposition of atomic TiO2 layer on chalcogenide nanorod with excellent activity and durability towards solar H2 generation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 341; pp. 335 - 343
• Main Authors: Liu, Maochang, Xue, Fei, Wang, Xixi, Fu, Wenlong, Wang, Yi, Lu, Youjun, Li, Naixu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2018
• Subjects: Core–shell structure; Electron tunneling; H2 production; Photocatalysis; Photocorrosion; H2 production; Electron tunneling; Photocorrosion; Core–shell structure; Photocatalysis
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2018.02.031

[Display omitted] •Ultrathin TiO2 shell was coated on chalcogenide nanorod as a protecting layer.•The synthesis relies on kinetic control for layer-by-layer deposition of TiO2.•The heterostructure enables superior activity and stability of solar H2 evolution.•Charge transfer is controlled by type-II band alignment and tunneling effect. It has been a subject of intensive research on avoiding photocorrosion of sulfide photocatalysts while retaining their activity for visible-light-driven photocatalysis. Herein, using Cd0.9Zn0.1S (CZS) nanorod as an example, we report an effective strategy based upon conformal coating of an ultrathin pinhole-free TiO2 shell, with controllable thickness from 2 to 7 nm, on the nanorod as protecting layer. The synthesis relies on the use of a syringe pump for kinetic control, by which, TiO2 can grow on the surface of CZS in a layer-by-layer mode. The core–shell heterostructures were found with excellent photocatalytic performance toward solar hydrogen production from a Na2S-Na2SO3 aqueous solution. The reaction can stably proceed for 200 h without notable decay of the hydrogen evolution rate. A volcano-type relationship between the mass activity and the shell thickness was gained either in the presence of a cocatalyst or not. The heterostructure with a shell thickness of 2 nm presented the highest H2-evolution activity with a quantum efficiency of 19%. However, the one with a shell thickness of 7 nm, instead, was found to be more active, with a quantum efficiency reaching 44%, when 1 wt% NiSx cocatalyst was introduced. It is believed that photogenerated electrons transfer from CZS to TiO2, while the holes vanish via quantum-tunneling-induced recombination with the electrons. This work suggests that sulfide photocatalysts with desirable efficiency and corrosion resistance could be achieved by introducing conformal atomic TiO2 layers.