Influence of natural carbon template on Ag-ZnO nanocomposites for enhanced supercapacitor, photocatalytic hydrogen production and antifungal activity

Abstract

Zinc oxide (ZnO) hexagonal nanorods and silver (Ag) - ZnO nanoplate like structures are synthesized by using novel natural carbon templates. The structural intricacies are evaluated with various characterizations which is utilized for supercapacitor and photocatalytic H₂ production under direct sunlight applications. The role of carbon template in silver ion dispersion on ZnO matrix which is reflected in XRD and optical measurements. The presence of Ag (111) plane in the ZnO matrix, as proved by XRD shifts the Fermi level which in turn facilitates electron transport from valence band to conduction band whilst it is useful for photocatalytic H₂ production. The UV-DRS shift in wavelength to visible region is observed with the introduction of silver on ZnO. The HRSEM and HRTEM reveals the presence of nanorods and plate like morphology with distinct Ag (111) lattice fringes. XPS gives insight about the oxidation state of Ag-ZnO nanocomposites which is also complimented from peaks in XRD and LSPR in UV-DRS. Silver presence in both oxidation state attributed to Ag₂O (Ag⁺) and metallic silver cluster (Ag⁰). The BET isotherm substantiates increased surface area for the Ag5 %-ZnO (PC) composite than Ag5 %-ZnO (Egg white-EW), since the former provides fine dispersion of Ag on ZnO matrix. The electrochemical investigations reveal that the material with higher surface area provide more active sites for superior specific capacitance (221.1 F g⁻¹) and high energy density (27.6 Wh kg⁻¹) with 88 % capacitance retention stability which is clearly evidenced from GCD analysis. The lower charge transfer resistance of Ag-ZnO nanocomposite is beneficial for energy conversion and storage applications. The usage of silver in ZnO enhanced the antifungal activity against aspergillus niger fungi.