TiO2-based photoanodes modified with GO and MoS2 layered materials

Abstract

MoS₂/TiO₂ and GO/TiO₂ nanocomposites were synthesized via environmentally friendly electrodeposition (GO, MoS₂) and – for the purpose of comparison – hydrothermally (MoS₂). The modified Hummers' method was used to form GO from expanded graphite. A hydrothermal process of MoS₂ preparation from Na₂MoO₄ and CH₄N₂S with the use of a surfactant or NH₂OH·HCl and NH_3(aq) was applied. The prepared powders were characterized by means of X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Both GO and MoS₂ were found to form 2D layered materials. Electrochemical deposition of two-dimensional compounds on the surface of TiO₂ was conducted with the use of a suspension of 2D MoS₂ or GO in KNO₃ (pH close to neutral) at 1.2 V for 40 s. Hydrothermal conditions were applied for MoS₂ deposition as well. The morphology and photoelectrochemical properties of GO- and MoS₂-modified TiO₂ photoanodes were studied, and measurements using electrochemical impedance spectroscopy were performed. Lower charge transfer resistance as well as a significant enhancement of photoelectrochemical response were confirmed for MoS₂/TiO₂ nanocomposites in comparison to TiO₂. The highest photocurrent was achieved for 2D/TiO₂ prepared with the use of MoS₂, characterized by a well-defined microstructure and higher crystallinity. Hydrothermally modified photoanodes were found to be stable under photoelectrochemical measurement conditions.