Fabrication and surface stochastic analysis of enhanced photoelectrochemical activity of a tuneable MoS sub(2)-CdS thin film heterojunction

• Published in: RSC advances 2016-02, Vol.6 (20), p.16711-16719
• Main Authors: Zirak, M, Ebrahimi, M, Zhao, M, Moradlou, O, Samadi, M, Bayat, A, Zhang, H-L, Moshfegh, A Z
• Format: Article
• Language: English
• Subjects: Density; Deposition; Fluctuation; Indium tin oxide; Molybdenum disulfide; Nanostructure; Surface chemistry; Thin films
• ISSN: 2046-2069
• DOI: 10.1039/c5ra26487a

A very simple and well-controlled procedure was employed to prepare CdS nanoparticle/few-layer MoS sub(2) nanosheet/Indium tin oxide (ITO) thin film heterostructures. To tune and fabricate the CdS/MoS sub(2)(t)/ITO thin films with various surface topographies, first electrophoretic deposition (EPD) was used to deposit MoS sub(2) nanosheets on the ITO substrate under an optimized applied potential difference (8 V) for different deposition times (t) of 30, 60, 120 and 240 s. Then, CdS nanoparticles were deposited viaa successive ion layer adsorption and reaction (SILAR) technique. The highest photo-current density of 285 mu A cm super(-2) was measured for the CdS/MoS sub(2)(60 s)/ITO sample, which was about 2.3 times higher than the value obtained for bare CdS/ITO. The photo-enhancement mechanism of the CdS/MoS sub(2)(t)/ITO heterostructures was described using a stochastic model. The results show that the CdS/MoS sub(2)(60 s)/ITO electrode exhibits the highest roughness exponent (2 alpha = 0.67) with the smoothest nanometric fluctuations, resulting in the best wetting properties, and thus, the highest interaction between the electrolyte and the sample surface, leading to the highest PEC activity. On the other hand, the samples with small alpha possess rough and nanometric-jagged fluctuations. The air trapping inside these microscopic surface fluctuations reduces the wettability as well as surface interaction between the sample and the electrolyte, resulting in low photo-current density.