Novel Cr and Sn co-doped Co₃O₄ polygon-based electrode material for supercapacitor application

Use of co-doped metal oxide-based materials for supercapacitor application is a novel approach to attain significantly enhanced capacitive properties. In this context, we are reporting here, the synthesis of Cr and Sn co-doped Co₃O₄ polygon-based material and its application in supercapacitor. The co-doped Co₃O₄ material was synthesized by varying the doping ratios of Cr and Sn as 3:7, 5:5 and 7:3 at.% respectively through hydrothermal synthesis route. Material and capacitive properties were studied for pristine and co-doped Co₃O₄ material. The crystalline structure, morphology and chemical composition were investigated by using XRD, SEM and EDX techniques, respectively. The XRD results revealed the formation of single cubic phase Co₃O₄ nanostructures with average crystallite size 40 nm. The SEM results explored the development of polygon-based nanostructures having sizes in the range of 40–50 nm. The EDX results exhibited the presence of only Co, Cr, Sn and O elements in the material thus proved the highly pure nature of this material. The electrochemical measurements were done with the help of CV, GCD and EIS techniques performed in a 3 M KOH electrolyte solution. The CV test revealed that, among the samples with doping ratios 3:7, 5:5 and 7:3 at.% of Cr and Sn in Co₃O₄ crystal lattice labeled as CrSnCo-1, CrSnCo-2 and CrSnCo-3, respectively, the CrSnCo-2 sample exhibited highest specific capacitance, i.e. 1413.56 Fg⁻¹ at 5 mVs⁻¹ and also showed excellent capacitance retention, i.e. 89.41% after 3000 CV cycles performed at a scan rate 5 mVs⁻¹. The GCD test showed the pseudocapacitive nature of the material with good stability, i.e. 77.38% (capacitance retention) at higher scan rate, i.e. 10 Ag⁻¹. Moreover, the EIS spectroscopy revealed the excellent conductive nature of CrSnCo-2 material. These results suggest its potential application in energy storage devices like supercapacitors.