Exploring the potential of binder-free synthesized cobalt-based phosphate hydrate and pyrophosphate electrodes for supercapacitors

Abstract

We used a hydrothermal approach to synthesize electrodes of cobalt phosphate hydrate (CPH) and cobalt pyrophosphate (CPP) on 3D Ni-foam. At a steady reaction temperature, the effect of hydrothermal reaction time (0.5 to 2.5 h) on the electrochemical performance of CPH and CPP electrodes is studied. The structural, morphological, and electrochemical characterizations of all the CPH and CPP electrodes were thoroughly investigated. X-ray diffraction (XRD), FTIR, and Raman study confirm the crystalline and amorphous nature of the synthesized CPH and CPP materials, respectively. The scanning electron microscopy (SEM) investigation reveals nanoflakes structures of all the electrodes. Electrochemical measurements of CPH and CPP electrodes were conducted in a 1 M KOH electrolyte over −0.2 to 0.55 V versus SCE (for CPH) and −0.2 to 0.3 V versus SCE for CPP. The CPH2 electrode, demonstrated a specific capacity of 244.4 mAh/g (1,173.33 F/g) at a current density of 30 mA/cm2. The charge storage dynamics of the CPH2 electrode is discussed using the power law. Furthermore, a hybrid supercapacitor is assembled with CPH/CPP and activated carbon (AC) for electrochemical measurements.