Bifunctional electro-catalytic performances of NiMoO4-NRs@RGO nanocomposites for oxygen evolution and oxygen reduction reactions

Abstract

In present study, we report hydrothermal synthesis of reduced graphene oxide (RGO) supported NiMoO4-nanorods (NRs) nanocomposites (NiMoO4-NRs@RGO nanocomposites) for electro-catalysis of water to oxygen evolution and reduction reactions (OER/ORR). The prepared nanocomposites were characterized by x-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), energy dispersive and x-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performances of NiMoO4-NRs@RGO nanocomposites were examined in 0.5 M KOH (alkaline electrolyte) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), Tafel and chronoamperometry (CA) electrochemical techniques at room temperature. The onset over-potentials of NiMoO4-NRs@RGO nanocomposite for ORR and OER were found to be of ~75 and ~185 mV, respectively, while the Tafel slopes for OER and ORR were observed to be ~54 and ~245 mV/dec respectively. The involved electrons (i.e. 4e−) in redox reactions were calculated using rotating disc electrode experiments. Based on admirable electro-catalytic performance of NiMoO4-NRs@RGO nanocomposites with low energy loss, suggesting it as cost effective and efficient OER/ORR electro-catalysts compared to noble metal electro-catalysts.