Exploration of anode candidacy of Ni0.2Co2.8O4 and integrated Ni0.2Co2.8O4/MWCNTs in supercapacitor and oxygen evolution reaction

Abstract

In the current research work, Ni0.2Co2.8O4 and Ni0.2Co2.8/MWCNTs have been synthesized via facile sol-gel and wet impregnation method. The synthesized materials attained the crystalline structures as evident from X-ray diffraction analysis (XRD). The uniform morphology and well dispersion of Ni0.2Co2.8O4 onto MWCNTs was observed via scanning electron microscopy (SEM). The electrochemical investigations for supercapacitor application by cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) revealed that, among both materials, Ni0.2Co2.8O4/MWCNTs has high specific capacitance (CV; 505.8 Fg-1 at 5 mV/s, GCD; 1598 Fg-1 at 0.5 A/g), greater capacitance retention (85 %) at 1000 cycles and has lower charge transfer resistance (Rct; 3.48 Ω cm2). These findings reflected the potential candidacy of Ni0.2Co2.8O4/MWCNTs to be used as anode material in supercapacitor. Further investigations by CV and linear sweep voltammetry (LSV) for oxygen evolution reaction (OER) activity in 1.0 M KOH showed comparatively low over potential of 340 mV @100 mA/cm2 for the same integrated material. Additionally, the lower Tafel slope (47 mV/dec) and solution resistance authenticated it as an appropriate electrocatalyst for OER in water splitting. The CPE (controlled potential electrolysis) revealed the stability of both materials for OER in water oxidation.