Structure and morphology modification of ZnO nanocrystals via substitutional cobalt doping for enhanced electrochemical activity

Abstract

This study investigated the electrochemical performance of the morphologically and structurally modified Co-doped ZnO nanocrystals synthesized via the chemical co-precipitation method. The structural properties were characterized by XRD, where the lattice parameters and volume got smaller with the increasing amount of Cobalt doping. The compositional analyses showed that 1.5 and 2.5 at% of Cobalt was present in the Co-doped ZnO nanocrystals. The FT-IR analyses showed that Zn–O (tetrahedral) and Zn–O (octahedral) vibrational modes are present for the precipitated ZnO-based nanocrystals. Besides that, the characteristic Raman spectra mode for ZnO displayed redshift, and more modes were activated, which showed a change in the defect chemistry after the cobalt substitution into the ZnO host lattice. A significant change was observed in morphology where the pristine ZnO formed nanoflower composed of nanoflakes and the Co-doped ZnO nanoparticles formed nanospheres. Lastly, cyclic voltammetry was performed at different scan rates where typical Faradaic peaks were observed for all the samples, and the electrochemical performance was increased with the small amount of Co doping into the ZnO lattice. The samples showed improved pseudocapacitive behavior, suggesting that Cobalt doped ZnO nanoparticles synthesized via the chemical co-precipitation method can be a potential electrode material for pseudocapacitor applications.