Structural, Morphological, and Electrochemical Investigation of Hydrothermally Synthesized Zinc Cobalt Oxide Nanoarchitectures for Bifunctional Electrochemical Supercapacitors and Non-enzymatic Glucose Sensing

Abstract

In the present investigation, we have successfully synthesized pristine cobalt oxide and zinc cobalt oxide nanostructures using the hydrothermal method followed by annealing treatment. The XRD study confirms the formation of the cubic spinel phase of cobalt oxide, and Zn-modified cobalt oxide samples exhibited minor lattice expansion supports the formation of zinc cobalt oxide. Further, the FTIR study confirms the structural integrity of cobalt oxide as well as zinc cobalt oxide. The morphological study using FESEM reveals that after Zn incorporation change in morphology, i.e., from nanosheet to nanoporous interconnected nanoparticles, was observed. An EIS study was employed to study the capacitive behavior and charge transfer kinetics of the pristine cobalt oxide and zinc cobalt oxide electrodes. The electrochemical performance was evaluated through CV and GCD measurements in a 1 M KOH electrolyte. The optimized ZNC-20 electrode exhibited the highest sp. capacitance of 549 F g⁻¹ at a current density of 2 mA cm⁻² and excellent cyclic stability of 81.16% over 5000 GCD cycles. Further, ZNC-20 electrodes reported excellent glucose sensitivity of 382 µA mM cm⁻². The overall structural, morphological, and electrochemical investigation confirms the Zn incorporation in pristine cobalt oxide, leading to superior electrochemical supercapacitor as well as non-enzymatic glucose biosensing performance.