TiO2-based photoanodes modified with GO and MoS2 layered materials
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 NH3(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.