Exploring optical and electrochemical studies on thulium selenite (TmSeO₃)

Abstract

Thulium selenite (TmSeO3) has been synthesized by precipitation method. It shows interesting smooth surface with nearly non-symmetric texture similar to water droplets spreading on hydrophobic surface. TmSeO3 is found to be monoclinic structure with lattice parameters a = 5.919±0.01 Å, b = 12.422±0.01 Å, c = 8.717±0.01 Å, α = γ = 90°, β = 106.01° and V = 616.1 Å3. Fourier transform infrared spectroscopy confirms the presence of Tm–Se bonding. X-ray photo emission spectrum confirmed the presence of thulium, selenium and oxygen in the samples in oxide form. Magnetic study between 300 and 20 K, shows decrease of magnetic moment with temperature, then reaches saturation and aligns all thulium spins. This results cooperative interaction of thulium spins. M–H curve at 300 K confirms the paramagnetic nature of sample. Cyclic voltammogram of three electrode system, manifests electric double layer capacitance with a potential window of 0.55 V. Specific capacitance is 102 F/g. Chronopotentiometry analysis shows 75 F/g specific capacitance, 11 Wh kg−1 energy density, and 275 W kg−1 power density. Impedance analysis confirms electric double layer capacitor behavior. Hence, TmSeO3 electrode based symmetric supercapacitor device was successfully fabricated and tested by two electrode configuration in aqueous electrolyte of KOH. A specific capacitance of 64.60 F/g at 1 A/g within a potential window of 1.85 V was achieved. Impedance analysis also confirms electric double layer capacitor nature with low series resistance of 0.2596 Ω and charge transfer resistance of 1.6352 Ω. The improved cycling performance after 4000 cycles is 51.5 % specific capacitance retention. Thus, symmetric supercapacitor electrodes based TmSeO3 materials are expected to have good electrochemical properties and good stability for energy storage and conversion applications. Furthur, optical parameters 5.28 eV energy gap, 0.4924 eV Urbach energy value and 1.959 refractive index are determined.