Metal-organic framework derived SrTi1-xCoxO3-δ as anion-intercalated electrode for supercapacitor

Abstract

Herein, we have synthesized Co-doped SrTiO₃ (SrTi_1-xCo_xO_3-δ) at ambient conditions using metal-organic framework (MOF) of constituent elements. Structural and charge storage characteristics of SrTiO₃ were optimized by Co-doping (0 ≤ x ≤ 3 %). Different morphological features i.e. nano-block to elongated nano-needles were obtained in SrTi_1-xCo_xO_3-δ by changing the Co concentration from 0 ≤ x ≤ 3 %. Being larger in size than Ti, Co doping expanded the interlayer spacing of (011) plane and enhanced the oxygen vacancy concentration to maintain charge neutrality. Among all, SrTi_1-xCo_xO_3-δ (x = 2 %) exhibited an exceptionally high electrochemically active surface area (ECSA) of 2388 m² g⁻¹, lowest optical band gap (2.7 eV), and highest specific capacitance (1311 F g⁻¹ @ 2 A g⁻¹). This is attributed to the rich electronic conductivity, and highest oxygen vacancy concentration (∼31 %) in SrTi_1-xCo_xO_3-δ (x = 2 %) which boosted the anion-intercalated energy storage. Fabricated symmetric (STCO||STCO) and asymmetric (STCO||Activated Carbon) cells resulted in an appreciable energy density of 38 Wh kg⁻¹ @575 W kg⁻¹ and 53.5 @1196 W kg⁻¹ with an operating voltage of 1.2 V & 1.3 V, respectively.