NiO nanoparticles decorated at Nile blue-modified reduced graphene oxide, new powerful electrocatalysts for water splitting

Abstract

New nanocomposites, containing nickel oxide nanoparticles (NiONPs) and Nile blue@reduced graphene oxide (NB/rGO), were synthesized. Nile blue was decorated on the surface of rGO by covalent bonds (using diazonium reaction). Then, NiONPs was immobilized on the surface of the functionalized rGO. The electrocatalytic and electrochemical behaviors of NiO@rGO and NiO@Nile/rGO nanocomposites for HER were investigated using cyclic voltammetry and electrochemical impedance spectroscopy in acidic and alkaline media. From them, NiO@rGO has shown long-term stability for HER in acidic solution at room temperature. The electrocatalytic activity of NiO@rGO (vs. NiO@Nile/rGO) for HER was greatly improved and its behavior was close to the behavior of platinum. In the next stage of our study, due to the importance of oxygen as an energy source, the production of oxygen molecules through electrochemical oxidation of water at NiO@rGO and NiO@Nile/rGO were studied too. For this purpose, the electrochemical behaviors of the nanocomposites for oxygen evolution reaction were investigated using cyclic voltammetry and electrochemical impedance spectroscopy in acidic and alkaline media. The results of them confirmed that NiO@Nile/rGO acts as an excellent electrocatalyst with good long-term stability for oxygen evolution reaction in 0.5 mol L−1 KOH solution at room temperature.Therefore, NiO@rGO and NiO@Nile/rGO can be used as powerful cathode and anode, respectively in an electrochemical cell for water splitting.