Cd0.5Zn0.5S Research Articles

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

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.

Fabrication of Excellent Heterojunction Assisting by Interfaced Oxygen Vacancy to Improve the Separation Capacity of Photogenerated Carriers

AbstractHeterojunction connecting by interface chemical bonds is a promising method as it can provide more efficient route for photogenerated charge separation. In this work, the oxygen vacancies are introduced into the surface of SrTiO3 by a one‐step hydrogenation method. SrTiO3 with oxygen vacancy (STO) is compounded with Cd0.5Zn0.5S (CZS) by hydrothermal method, resulting in the successful formation of a good heterojunction structure. By comparing with the pristine SrTiO3/CZS composites, it is found that the oxygen vacancies play an important role in the formation of excellent heterojunctions, in addition to the traditional reports as charge traps and adsorption sites or the ability to cause band changes. X‐ray photoelectron spectroscopy (XPS) and high‐resolution transmission electron microscope results disclose that S2− enters the oxygen vacancy on the (110) plane of STO and interacts with the adjacent Ti in the van der Waals force to form the Ti‐O‐S group, which results in the formation of excellent heterojunctions and makes the CZS nanoparticles growth evenly on the STO nanoplates. Furthermore, the formation of excellent heterojunction and the introduction of interfaced oxygen vacancy significantly improve the separation efficiency of photogenerated charge carriers, which dramatically increases the photoelectrochemical performance.