Synthesis of ZnO/C Nanocomposites via Liquid-Assisted Laser Ablation in an Applied Electric Field for Supercapacitor Applications

Abstract

The formation of nonspherical anisotropic nanoparticles having a large surface area by pulsed laser ablation in liquids (PLAL) still remains a challenge. In this work, to expand the capabilities of the PLAL technique, an approach was developed based on pulsed laser ablation in liquids with an external voltage applied to the target. This approach allowed shape-controlled preparation of nonspherical ZnO/C composite nanomaterials providing additional possibilities for tuning of the particles’ morphology that was found to depend on the applied voltage and polarity. The positive polarity on the Zn target allowed obtaining nanodisk structures, whereas application of negative polarity to the target enabled the formation of flower-like nanostructures proven by scanning (SEM) and transmission electron microscopy (TEM) studies. The optimal conditions for the nanoflower formation were found with the voltage set to be 200 V. A time-resolved imaging technique was applied to study plasma propagation evolution and lifetime that allows suggesting the mechanisms of nanoflower formation. Furthermore, utilizing the developed approach in a carbon nanoparticle colloid, sponge-like composites were obtained having a developed surface that showed promising capacitance and charge storage behavior in preliminary electrochemical tests. The ZnO/C composite structures were evidenced by SEM and TEM studies as well as by EDX mapping, X-ray diffraction, Raman, infrared, and optical absorption spectroscopy measurements. In addition, the production of particles in the presence of an electric field leads to the deposition of the formed nanostructures on the cathode surface that can serve as a tool for assembling the resulting particles into ordered structures for subsequent supercapacitor applications.