Synthesis and characterization of ZnO-NiO nanocomposites for photocatalytic and electrochemical storage applications.

Three different ionic surfactants (CTAB, SDS, and PEG) were capped synthesized ZnO-NiO nanocomposites via co-precipitation method. The primary goal of the present work is tuning the crystallite size, morphology, particle size, energy gap, and luminescence of ZnO-NiO nanocomposites under the influence of surfactant agents through powder XRD, SEM, UV–visible, and fluorescence measurements. The bi-phase crystalline structure has been identified in synthesized ZnO-NiO samples with the assistance of powder XRD analysis. The TEM image of the CTAB-capped ZnO-NiO composite revealed a uniformly dispersed spherical-like structure of the particles. Further, formations of zinc oxide–nickel oxide have also been supported by the EDX study. The optical band gap values are relatively higher (3.17 eV) in CTAB-capped ZnO-NiO composites than SDS-capped (3.12 eV), and PEG-capped (3.10 eV) through identified as UV–visible spectra. From the fluorescence spectra, strong visible emission peaks were detected at 632 nm in all synthesized ZnO-NiO nanocomposites. The second aim of the present work, in terms of the better size and optical properties of CTAB-capped ZnO-NiO composites, has been taken to further investigate photocatalytic and electrochemical properties through photocatalytic experiments and cyclic voltammetry measurements. Orange Gelb (OG), Amidoblack 10B (AB10B), and Direct Blue 71 (DB71) dyes, along with CTAB-capped ZnO-NiO nanocomposites, were employed as photocatalyst in a photocatalytic experiment under visible light illumination to test the photodegradation efficiency. Photodegradation efficiency of AB10B to be 99.145% is relatively higher than 95.92% (OG) and 94.88% (DB71) which is due to the photo absorption wavelengths of the chromophore and aromatic part of the dyes. In addition, the electrochemical oxidation peaks, current response, and corresponding potential of CTAB-capped ZnO-NiO were shifted under the influence of various scan rates using cyclic voltammetry (CV) analysis, which exhibits pseudocapacitance behavior. This work will pave the way for the synthesized sample's use in waste-water treatment and supercapacitor applications. [ABSTRACT FROM AUTHOR]