Sol-gel combustion synthesis of porous Mg2SnO4@SnO2 nanocomposites: A study on the structural parameters, optical properties, and electrochemical activity

In this work, a magnesium stannate-tin oxide nanocomposite (Mg2SnO4@SnO2) was prepared using the sol-gel combustion method. The physical properties of the products have been characterized by different analysis techniques. The XRD results revealed the combined structure of the cubic inverse spinel phase of Mg2SnO4 and the tetragonal phase of SnO2 with a mean crystalline size of 5.1 nm. The average grain sizes of SnO2 and Mg2SnO4@SnO2 from FESEM images were about 51.98 nm and 58.18 nm, and TEM images revealed that the size of nanoparticles were about 30-200 nm and 20-50 nm, respectively. The band gap energy of Mg2SnO4@SnO2 NPs was estimated to be about 3.9 eV. Results from FESEM and BET revealed the sample's sponge-like meso/ macroporous morphology. PL spectra have revealed a blue emission. The optical constants of Mg2SnO4@SnO2 deposited on the glass substrate were determined using UV-Vis transmittance data and theoretical approaches. The electrochemical performances of the porous Mg2SnO4@SnO2 deposited on ITO-coated glass substrate and metal foam (Ni and Cu) substrates as particulate composites by doctor blade technique were compared by GCD, CV, and EIS analysis. The best performance is belonged to the Mg2SnO4@SnO2/Cu foam electrode with a specific capacitance of 675 Fg-1 at a current density of 1 Ag-1. Mg2SnO4@SnO2/Ni foam has a higher capacitance retention rate, which showed stability of 86.27 % over 5000 charge/discharge cycles at a current density of 10 Ag-1.