PVP assisted morphology-controlled synthesis of hierarchical mesoporous ZnCo 2 O 4 nanoparticles for high-performance pseudocapacitor

ZnCo2O4 nanoparticles (NPs) with four different and unique morphologies were synthesized using different mass ratio of polyvinyl pyrrolidone (PVP) with respect to metal oxides: 0.55 wt% PVP (P1), 1.09 wt% PVP (P2), 1.64 wt% PVP (P3) and 2.18 wt% PVP (P4), through a facile hydrothermal process followed by heat treatment and used as electrodes for high performance pseudocapacitor. In this study, PVP served as surface stabilizer and growth modifier during NPs synthesis. Each mass ratio of PVP with respect to metal oxides resulted to different unique morphologies: rods, ring, oval "rice grain", and hexagonal-like shape composed of numerous ZnCo2O4 NPs. The resulting products were analyzed by using thermo gravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron micrographs (FE-SEM) coupled with energy dispersive X-ray spectrometer (EDX), high-resolution transmission electron microscopy (HR-TEM) and Brunauer-Emmett-Teller (BET). ZnCo2O4 NPs with ring-like morphology (P2) showed the highest specific capacitance of 2834.18 F g−1 at a scan rate of 2 mV s−1. Additionally, P2 material also showed the highest specific capacitance of 1152.19 F g−1 at a current density of 5 A g−1 and displayed excellent cycling ability even after 3000 cycles at 50 mV s−1 scan rate.