Microwave-assisted synthesis of Ru and Ce doped tungsten oxide for supercapacitor electrodes

Abstract

Ruthenium (Ru) and cerium (Ce) doped tungsten oxide (WO3) were successfully synthesized at various concentration (1–5 wt.%) by microwave irradiation method without adding any surfactant and studied as a supercapacitor electrode material for the first time. The effect of Ru and Ce on structural and morphological properties were studied systematically by using powder X-ray diffraction (XRD), thermogravimetry (TG)-differential thermal analysis (DTA), scanning electron microscopy (SEM) and tunneling electron microscopy (TEM). Powder XRD analyses reveal the formation of orthorhombic structure for the as-synthesized pure and doped WO3. Annealing at 500 °C modifies the structure of the as-synthesized materials from orthorhombic to monoclinic. TG-DTA shows the elimination of water at around 170 °C which confirms the structural change of orthorhombic to monoclinic. TEM images shows that the doping in WO3 affects the morphology, changing form hexagonal shape to elongated spherical shape and flake-like nanoclusters in Ru and Ce doped WO3, respectively. The electrochemical measurements of cyclic voltammetry, galvanostatic charge–discharge and impedance were performed in a three-electrode configuration to assess the electrochemical performances of the synthesized materials for supercapacitor applications. Among all the doping, 2 wt.% Ce doped WO3 shows a high specific capacitance value of 52 F g−1 at a current density of 0.1 A g−1. The energy density is found to be 5.49 W h Kg−1 for W0.98Ru0.02O3 and 7.22 W h Kg−1 for W0.98Ce0.02O3 at a power density of 50.08 W Kg−1 and 49.22 W Kg− 1, respectively.