Abstract

Hydrothermally synthesized strontium titanate (SrTiO₃) nanocubes were subjected to microwave kiln-assisted annealing (MWA-kiln) in a domestic microwave oven (800 W, 10-60 min) to investigate structural refinement and electrochemical performance. First-principles density functional theory calculations within the local density approximation supported the experimental findings. Electrochemical performance and cycling stability were evaluated by cyclic voltammetry and galvanostatic charge–discharge measurements. Treatment for 20 min produced optimal crystallinity, reduced microstrain, the highest surface area (17.49 m² g^-1), a higher oxygen-vacancy concentration, and a band gap reduction from 3.72 to 3.67 eV, enabling mixed capacitive and diffusion-controlled charge storage. In a three-electrode configuration, SrTiO₃-MWA-20 delivered 127.62 F g^-1 at 5 mV s^-1 and 64.38 F g^-1 at 0.4 A g^-1, outperforming the untreated sample. A hybrid coin cell combining SrTiO₃-MWA-20 with activated carbon (AC), designated SrTiO₃-MWA-20//AC, delivered 100.38 F g^-1 at 5 mV s^-1 and 35.73 F g^-1 at 0.4 A g^-1, with an energy density of 6.95 Wh kg^-1 at 200 W kg^-1. These findings establish MWA-kiln as a rapid, energy-efficient, and sustainable method for optimizing perovskite oxides and identify SrTiO₃ as a promising electrode material for next-generation supercapacitors.