Preparation of two-dimensional MoSe2/polypyrrole nanocomposites-based catalysts and their application in electrochemical water splitting reactions

Electrochemical water splitting process is one of the most promising methods for hydrogen production. In electrochemical water splitting reactions, noble metals-based materials have been generally used as catalysts to efficiently produce hydrogen, whihc limit their practical application. Therefore, it is highly important to develop nonnoble metal-based electrocatalysts and apply them in electrochemical water splitting processes. In this thesis, molybdenum diselenide (MoSe2) and polypyrrole (PPy)-based electrocatalysts were prepared by hydrothermal method and their electrocatalytic performances in electrochemical water splitting reactions were investigated. Structural and morphological characterizations of as-synthesized materials were performed by Fouirer transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Analysis results revealed the formation of MoSe2 in two-dimensional nanosheet structures and also confirmed the presence of PPy in hybrid structures. The fabricated electrocatalysts were applied in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) and it was found that in the HER Co-MoSe2@PPy/NF showed better electrocatalytic performance than other catalysts with over potential values of 203 mV/dec at 10 mA/cm2 current density, while MoSe2@PPy/NF exhibited the lowest overpotential of 310 mV at 10 mA/cm2 for the OER. In addition, important performance parameters such as Tafel slopes, charge transfer resistances (Rct) and electrochemical active surface areas (ECSA) of the developed catalysts were also determined. Finally, stability tests of the best-performing electrocatalysts were performed and it was found that Co-MoSe2@PPy/NF in the HER and MoSe2@PPy/NF in the OER electrocatalysts displayed negligible loss in their activities after 1000 continuous cycles by cyclic voltammetry.