Preparation and Photoelectrochemical Properties of Multilayered WS2 Coated Titanium Dioxide Nanocomposites

Since TiO₂ was discovered for water-splitting to generate hydrogen under UV light, plenty of techniques have been explored to obtain suitable sensitizers for visible-light adsorption in order to increase the activity of water-splitting reaction for hydrogen generation [1-3]. Among them, dispersing a 2D graphene andsimilar layered material on TiO₂ nanoparticle exhibits highly photocatalytic activities (i.e. MoS₂) [2].

In this paper, graphene-liked WS₂ was chosen due to its activity as HER (hydrogen evolution reaction) catalyst and relatively abundant storage [4]. The expected composite was formed through high energy ball milling technique which makes WS₂ disperse on the surface of TiO₂nanoparticles [5].

The composites consist of 99.5% TiO₂ and 0.5% WS₂and were prepared by high energy ball milling for five different periods of time-2hours, 4hours, 8hours, 16hours and 32hours. To identify phase evolution of the as-prepared nanocomposites during high energy ball milling procedure, X-ray diffraction (XRD) was performed to examine phase transition, which is shown in Fig.1. It can be seen that, with increasing milling time, the crystallization decrease at first and increase after further milling.

To further study the photoelectrochemical (PEC) characterization of composites after ball milling, a three-electrode setup was used, which is shown in inset of Fig. 2. This three-electrode device consists of a reference electrode (Ag/AgCl), a Pt wire counter electrode, a quartz container filled of 0.5M Na₂SO₄ aqueous solution and a working electrode. Sintered composites on indium-tin-oxide (ITO) glass substrate acts as the working electrode. Fig.2 shows the PEC measurement results of pure TiO₂ and milled composites with milling time for 2hours, 8hours and 32hours. As can be seen, composite reaches the best photocurrent response with 8 hours milling. It is obvious that compared to pure TiO₂ sample, adding of WS₂and high energy ball milling make positive effect to composites.

In summary, the structure of TiO₂ and WS₂ nanocomposites through high energy ball milling has been studied by X-ray diffraction. Photoelectrochemical properties of the TiO₂ coated with few layered WS₂ shows the optimization photochemical response for 8 hours milled nanocomposites. This work provides a facile and low cost process for large amount production of few layer doped TiO₂nanocomposites.

References

[1] A. Fujishima, K. Honda, Nature, 238 (1972) 37.

[2] Q. Liu, Z. Pu, A. M. Asiri, A. H. Qusti, A. Q. Al-Youbi, X. Sun,. J Nanopart Res 15 (2013) 1.

[3] W. Zhou, Z. Yin, Y. Du, X. Huang, Z. Zeng, Z. Fan, & H. Zhang, Small, 9(2013) 140.

[4] D. Merki, X. Hu, Energ Environ Sci, 4 (2011) 3878.

[5] H. C. Nazareno, Y. Zhao, K. Wang, IEEE Nano (2014)