Synthesis of double perovskite La2MnNiO6 nanoparticles as highly efficient oxygen evolution electro-catalysts

Abstract

Double perovskite La2MnNiO6 nanoparticles (approximately 30 nm in diameter) were synthesized using a modified sol-gel method followed by a firing process and used as promising electrode materials for oxygen evolution reactions (OERs). The phase purity of the nanoparticles was verified using X-ray diffraction and Raman spectroscopy measurements. La2MnNiO6 nanoparticles crystallize in a monoclinic structure (P21/n space group) with refined lattice parameters of a = 5.461(5) Å, b = 5.512(3) Å, c = 7.760(5) Å, and β = 90.10(2)°. The elemental composition, particle size, size distribution, and surface area of the La2MnNiO6 nanoparticles were also investigated. La2MnNiO6 nanoparticles are ferromagnetic in nature and exhibit hysteresis with a saturation magnetization value of approximately 9 emu/g. La2MnNiO6 nanoparticles exhibit highly efficient electro-catalytic activity for OERs with a low onset over-potential (approximately 65 mV) and low Tafel slope values (120 mV/dec) in alkaline media. The over-potential of La2MnNiO6 nanoparticles at a current density of 10 mA/cm2 is in good agreement with the reported over-potential (ƞ10) of double perovskites, commercial Pt/C and IrO2 electro-catalysts for promoting OERs.