Surfactant assisted-SnO2 nanorods and nanoflowers synthesised by hydrothermal method for supercapacitor applications

In this article, using polyvinyl alcohol (PVA) and sodium hexametaphosphate (SHP) as a surfactant solution, tetragonal SnO2 nanoparticles (NPs) were synthesised using the hydrothermal technique. NPs resulting from this process are named Sn-SHP and Sn-PVA.X-ray diffraction study revealed tetragonal crystal structure for both Sn-SHP and Sn-PVA nanoparticles, matching well with the JCPDS Card No. 88-0287. Scanning electron microscopy (SEM) showed rod-shaped Sn-SHP NPs, whereas Sn-PVA NPs have flower-like forms. A band gap energy of 3.71 and 3.84 eV was measured for the Sn-SHP and the Sn-PVA nanoparticles. The various oxidation states of SnO2 were confirmed by XPS spectra in order to confirm its oxidation states. The electrodes were analysed by using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical ion spectroscopy (EIS) in 6 M KOH electrolytes. For Sn-PVA electrodes, the computed specific capacitance (Cs) values are 330.52, 71.25, 27.34, and 18.85 Fg−1 at scan rates of 2, 10, 30, and 50 mVs−1; whereas for Sn-SHP electrodes, the obtained values are 256.24, 55.46, 21.04, and 14.45 Fg−1 at scan rates of 2, 10, 30, and 50 mVs−1. Additionally, from the GCD curves demonstrate that the Sn-PVA electrode has Cs of 126, 98, 81, and 71 Fg−1, and Sn-SHP electrodes revealed Cs of 75.65, 66.44, 48.69, and 25.97 Fg−1 at current density of 1, 2, 4, and 6 Ag−1, respectively. Galvanostatic charge–discharge curves for Sn-SHP and Sn-PVA NPs were traced in a potential window ranging from 0.03 to 0.4 V, and it was ascertained that Sn-PVA with flower shaped nanoparticles retains Sc of 126 Fg−1 at current density of 1 Ag−1, making it potential candidate for supercapacitor applications.