First principles and experimental study on MoS2-BASED nanocomposites for fuel cell application

Abstract

Energy storage via the combination of hydrogen production and fuel cell has been a very active field of research for the last few decades. Nanostructured semiconductor materials are now being utilized for hydrogen production and environmental remediation. Transition metal dichalcogenides (TMD) have generated tremendous interest as semiconducting materials in the recent times and Molybdenum disulfide (MoS2) is considered as an emerging TMD material. In the present work, a combined numerical and experimental study is conducted to examine the microstructural characteristics, potential and underlying physical mechanism of a novel graphene-MoS2-Fe2O3 nanocomposite in hydrogen production and degradation of chemical effluents.

First-principles calculations, based on density functional theory (DFT) using CASTEP platform, are performed to investigate the properties of graphene-MoS2-Fe2O3 nanocomposite and gain insight into the role of the individual components on its overall photocatalytic performance. The band structure, density of states, electron density, optical properties, and different thermodynamic properties of the individual components and their composites are investigated in detail. Introduction of graphene into the MoS2 semiconductor is found to improve the overall thermodynamic properties of the composite as graphene preserves its excellent properties. A projected density of states analysis reveals that multipoint electron transfer from graphene to MoS2 system can decrease the recombination of charge carriers. These results corroborate the hypothesis of the potential of using graphene-MoS2 as a co-catalyst to obtain better hydrogen production under visible light irradiations. This hypothesis is further examined by adding Fe2O3 to the simulation cell and it is observed that the bandgap position of Fe2O3 is shifted towards more favorable limit in the visible light region. In order to examine the ability and suitability of the graphene-MoS2-Fe2O3 nanocomposite for hydrogen production via water splitting method, the nanocomposite is synthesized, and the structural and morphological characterization of the fabricated samples is performed. The fabricated Graphene-MoS2-Fe2O3 nanocomposite exhibits excellent photocatalytic activity as about 96% of synthetic Rhodamine B (RhB) dye is degraded in 40 minutes. Finally, hydrogen production ability of the graphene-MoS2-Fe2O3 nanocomposite is examined and the fabricated nanocomposite is found to produce about 55 μmol of hydrogen gas /g of catalyst in 3 hours under gas chromatography analysis.

The findings of the present study have provided significant insight into the properties of graphene-MoS2-Fe2O3 nanocomposite and hence the suitability and potential performance of this nanocomposite in fuel cell and other applications.