Oxidative Disproportionation of MoS₂/GO to MoS₂/MoO_3–x/RGO : Integrated and Plasmonic 2D-Multifunctional Nanocomposites for Solar Hydrogen Generation from Near-Infrared and Visible Regions

Abstract

Two dimensional (2D) semiconductor materials have been recently demonstrated to be effective plasmonic materials and alternatives to costly noble metals. However, tuning the plasmon resonance of 2D semiconductors and integrating with another material or semiconductor for various applications, such as solar light harvesting, remains a challenge. Herein, we designed a simple and attractive method, which facilitates the diffusion of oxygen from the graphene oxide (GO) layers of the MoS 2 /GO (MG) composite to oxidize the MoS 2 layers significantly due to thermal treatment under inert atmosphere. This is the key step in the formation of MoS 2 /MoO 3−x / RGO (MMR) (x = 0, 0.5, and 1, and all stoichiometries co-exist), due to disproportionation of MoS 2 /GO, with bulk heterojunctions among the components. The observed behavior is attributed to the oxidation of Mo 4+ cations (of MoS 2 ) to higher oxidation states in MMR (Mo 5+ and Mo 6+ of MoO 3−x ), which also alters the valence-band electronic structure and work function of the resulting composite. The 2D MoO 3−x layers with a large amount of Mo 5+ oxidation states enables facile charge carrier generation due to plasmonic effect, whereas MoS 2 provides active sites for catalysis. The solar H 2 generation was demonstrated in the visible and near-infrared region by combining both the plasmonic and catalytic effects in one composite. These results demonstrate the important role of RGO to provide energy-level alignment, charge carrier diffusion, and help to generate plasmonic effect in the composite.

Rationally Designed, Efficient, and Earth-Abundant Ni–Fe Cocatalysts for Solar Hydrogen Generation

“…In addition, interconnectivity/Schottky junction (evidenced by TEM micrograph) formation at the interface of Ni–Fe cocatalyst and TiO 2 NPs is very crucial for effective charge separation and hence better utilization of electrons. Generally layered 2D materials, , such as graphene oxide, MoS 2 helps for charge separation and dispersion toward redox sites; indeed, MoS 2 acts as cocatalyst too and exhibits a HER of 131 μmol·h –1 ·g –1 . Nonetheless, the result from the present investigation is superior due to the employment of thin film methodology.…”

Enhancement of photocatalytic by Mn3O4 spinel ferrite decorated graphene oxide nanocomposites

“…Because of the difference in the mobility's of the electrons and holes, charge separation will occur and when this happens, one encounters a suppression of the annihilation of electron/ hole pairs and therefore an increase in the photo-catalytic activity. This was the explanations given by Patra et al [80], for the enhanced solar generation by MoS 2 /GO and MoS 2 / MoS 3-x /GO multi-functional NC's, for solar water splitting by Au-Pd/rGO/TiO 2 hetero junctions by Tudu et al [81], and by Au-RGO/N-RGO-TiO 2 hetero junctions by Bharad et al [82].…”

High-performance lateral MoS2-MoO3 heterojunction phototransistor enabled by in-situ chemical-oxidation

“…1e the electron and hole diffusion, causing the electrons to flow exclusively in one direction and across it. Based on its properties, the structure can be used as semiconductor diode for rectification in the applications in LEDs, analog and digital circuits (ICs) [35][36][37][38].…”

“…Originating from the increase of electron concentration in MoO 3 , Fermi level of MoS 2 moves closer to the conduction band edge, and significant charge transfer causes downward band bending. This phenomenon is very important for the application in logic circuits and high-performance optoelectronics based on p-n junction [38,39].…”