Fabrication and characterization of mixed metal sulfide thin films for photoelectrochemical application

Lau, Kelvin Ching (2020) Fabrication and characterization of mixed metal sulfide thin films for photoelectrochemical application. Master dissertation/thesis, UTAR.

Preview

PDF Download (22Mb) | Preview

Abstract

The M-doped (M = Fe, Co or Ni) thin films deposited on FTO substrate were prepared from AACVD process with dual precursors of [(ƞ5-Cp)Mo(SMe)2]2 (2) (Cp = C5H5) and Cp2M in THF under Argon at 550 °C in 20 min. The Cp2M worked as dopant was added in different mol%. The structure of the films was determined by XRD where rhombohedral MoS2 and monoclinic Mo2S3 were observed in all films. The Fe-, Co- and Ni-doped thin films also showed the presence of monoclinic Fe(MoS2)2, monoclinic Co(MoS2)2 and rhombohedral Mo3NiS4, respectively. In the Raman Spectroscopy, all films showed similar bonding mode despite having different dopants. In the XPS spectroscopy, Mo3+, Mo4+ and S2- were observed in all films. From the 10 to 40 mol% Fe-doped thin films, it showed both Fe2+ and Fe3+ was detected while 80 and 100 mol% showed only the presence of Fe2+. Co2+ was present in all Co-doped thin films while Ni2+ and Ni3+ were observed in all Ni-doped thin films. The EDX analyses showed that the dopants were lower than their theoretical values. The FESEM and the 2D AFM analyses showed all the Fe- and Co-doped thin films had a granular morphology from the top view while the 3D AFM analyses showed the present of standing nanorod arrays. However, for Ni-doped thin films a transition from granular to flake morphology were observed from 40 mol% Ni-doped onwards. The optical properties of the thin films were analyzed using UV-Vis spectroscopy where three band gaps at 1.60, 1.90 and 2.30 eV were determined. The PEC studies showed at the overpotential of 0.6 V that the 10 mol% Co-doped thin film gave highest photocurrent density of 2.497 mA/cm2 followed by the 40 mol% Fedoped and 10 mol% Ni-doped thin film at 1.645 mA/cm2 and 1.560 mA/cm2, respectively.

Actions (login required)