Abstract
Abstract These days, the environmental friendly electrochemical energy storage systems such as supercapacitors have been attracting a great attention to mitigate the energy crisis. The present work deliberated the resourceful synthesis of pure and Sr doped lanthanum nickel oxides (LaSrxNi1−xO3) by citrate gel auto-combustion route. The calcinations temperature of the citrate-gel precursors to obtain the pure and Sr doped LaNiO3 materials is ascertained by Thermogravimetric analysis as 750 °C to obtain the monophasic LaNiO3 and LaSrxNi1−xO3 materials. The structural, functional, morphological and optical properties of the synthesized LaSrxNi1−xO3 materials are determined by various characterization techniques like X-Ray Diffraction (XRD) spectroscopy, Fourier Transformed-Infra Red Spectroscopy (FT-IR), Scanning Electron Microscopy-Electron Diffraction Spectroscopy (SEM–EDS) and Ultra Voilet-Diffuse Reflectance Spectroscopy(UV-DRS) techniques with special reference to the effect of doping Sr metal. All the XRD diffraction peaks of the synthesized materials revealed the pervoskite-like crystal structures on comparing with standard JCPDS database No. 34-1028 with fine spindle to pseudo honeycomb like porous morphology. The IR bands at 540 cm−1 and 730 cm−1 represented the Ni–O stretching and Sr–O stretching vibrations respectively. The band gap energy (Eg) of the materials was calculated from their UV-DRS spectra using Tauc’s relation. The band gap energy of LaNiO3 (2.12 eV) was found to be decreasing on gradual increase of Sr contents and found to be lowest in LaSr0.8Ni0.2O3 (1.88 eV). The electrochemical properties of the synthesized material electrodes are investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) in aqueous electrolyte (1 M Na2SO4). The doping of Sr in LaNiO3 is found to be productive to improve the electrochemical properties of the material. Among the studied electrode materials, the LaSr0.8Ni0.2O3 material with highest Sr content demonstrated superior specific capacitance values 564 Fg−1 and 540 Fg−1 by CV and GCD studies at a current density of 1 Ag−1 with 83% retention of capacitance up to 10,000 cycles. Also, LaSr0.8Ni0.2O3 material exhibited a lowest ‘electrolyte resistance (Rs = 1.67 Ω) and charge-transfer resistance (Rct = 3.99 Ω)’ and identified as a better electrochemically active material for supercapacitor application. Graphical Abstract