Tunable Dielectric Carbon Materials from Hydrothermally Nanostructured Organic Carbon Sources

This work presents a systematic study of the electronic response and physico-chemical characteristics from hydrothermally treated organic carbon sources (banana peels and cocoa husks). Both samples are exposed to 150 °C and 210 °C for 2, 4, and 6 hours. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and conductivity measurements are used to describe the electronic properties for each organic carbon source. A multicategorical statistical optimization model let us to identify the best dielectric performance considering: a) temperature treatment, b) exposure time, c) frequency, and d) the organic carbon source. Our results indicate that cocoa husk hydrothermally treated samples (CHH) exhibited the best dielectric response, originating from high carboxyl concentrations or diamond-like carbon structures at 150 °C for 6 and 2 hours. In contrast, banana peel hydrothermally treated samples (BPH) are good conductors in comparison to CHH, due to low carboxylation or highly graphitization. This study provides valuable insights into the fundamental structure of lignocellulosic carbon sources that can aid in the development of energy storage and microwave technologies by transforming agricultural residues into high-value electronic materials.