Oxygen evolution kinetics, supercapacitor and display applications of Europium doped ZnSnO3 nanoparticles

Abstract

ZnSnO₃ doped with Eu²⁺ and Eu³⁺ is among the few host materials capable of accommodating both Eu³⁺ and Eu²⁺ ions, making it a promising candidate for white light-emitting diodes (WLEDs). In this communication, spinel cubic ZnSnO₃: Eu³⁺ (1-9 mol%) NPs are synthesized by Aloe vera mediated solution combustion method followed by calcination at 600^oC for 3hrs. The crystallite size decreases from 14.09 to 7.66 nm with an increase in dopant concentration. The surface morphology examined from field emission scanning electron microscope consists of bigger and smaller irregular-sized and shaped NPs with agglomeration. The optical energy band gap determined from Tauc's plot was found to be increased from 3.078 to 3.083 eV with an increase in dopant concentration. The photoluminescence (PL) emission excited under 311 nm consists peaks at 415 and 493 nm which can be attributed to 4f₆5d₁(T${}_{2g}$) → 4f⁷⁸S_7/2 transition of Eu²⁺. The another emission peak appeared at 628 nm corresponds to ⁵D₀ → ⁷F₂ transition of Eu³⁺ ion. The existence of Eu²⁺ and Eu³⁺ is further confirmed through the X-ray photon spectroscopy measurements. The CIE coordinates lie well within the white region. The average CCT value is 7114 K showing a cooler appearance. Thus the synthesized sample might be a promising candidate in display as well as in white light-emitting diodes. Oxygen evolution reaction (OER) investigations confirm the exceptional performance of ZnSnO₃:Eu (1-9 mol%) nanoparticles, showcasing impressively low overpotentials (318-333 mV) and minimal Tafel slopes (56-63 mV/dec). Chronoamperometry analysis demonstrates remarkable electrochemical stability over 20 hours with a consistent current density of 24.05-16.80 mA/cm⁻². Cyclic voltammetry analysis reveals insights into redox reactions, electrode kinetics, and overall electrochemical behavior. Improved ionic transport and supercapacitance performance (47.1 -101.3 F/g) at lower scan rates indicate potential applications in energy storage and display technology.