Carbon Nanofibrous Binary and Ternary Composites as High-Performance Electrodes for Supercapacitors

Abstract

In response to climate concerns and the global energy crisis, the focus has shifted to renewable energy sources like solar and wind power. However, their intermittent nature creates a challenge in matching energy supply with demand. Electrochemical energy storage devices, especially supercapacitors, offer advantages over batteries but lack high energy density. Scientists are tackling this by developing electrode materials with high capacitance and optimizing electrode architecture. The goal is to enhance supercapacitors' energy density while maintaining safety and power density, paving the way for more efficient and eco-friendly energy storage solutions. This doctoral dissertation is devoted to the advancement of high-performance supercapacitors through the utilization of cutting-edge carbon-based materials, electrochemically stable metal oxides. The aim is to tackle and surpass the limitations typically associated with supercapacitors. In the present study, two dimensional MXene embedded carbon nanofiber (CNF) and pseudocapacitive material (metal oxides & conductive polymers) composites are synthesized using different techniques such as electrospinning, electrodeposition, and in-situ polymerization. Prepared electrode surface morphology, chemical composition, and microstructure analysis were performed using a range of techniques such as FESEM. HRTEM, XRD, FTIR, and BET surface area analysis. A thorough assessment of electrochemical performance was carried out using both two- and three-electrode systems using synthesized binary and ternary composites as electrode materials for the symmetric supercapacitor. The first objective of the thesis deals with the synthesis of ruthenium oxide/MXene/CNF ternary nanocomposite using a facile electrospinning method. CNF is a host material in this nanocomposite, which acts as a backbone to the ruthenium oxide (RuO2) and MXene. The electrochemical performance of the ternary composite electrode is investigated. The second aim involves synthesizing a polyaniline (PANI)/MXene/CNF core and shell ternary nanofibrous electrode. The core consists of MXene-embedded carbon nanofiber, while the shell is formed by PANI through the in-situ polymerization method. The electrochemical performance of electrodes with PANI coating for various times is investigated. The third attempt demonstrates the cobalt oxide (Co3O4) /MXene/CNF hollow nanofiber composite using core and shell electrospinning technique. Carbon nanofibers with embedded MXene and coated with cobalt oxide are used as high performance electrodes for symmetrical supercapacitors. vi The fourth objective demonstrates a facile technique to synthesize Co-based metal organic framework MOFs and MXene embedded in CNFs. The electrochemical performance of electrodes with and without MOF was investigated and compared. The fifth objective deals with the development of an artificial neural network model for the prediction of carbon nanofibrous supercapacitors' performance. We have used a data driven Artificial Neural Network (ANN) model to predict the performance of CNF electrodes based on the material microstructural properties and electrochemical operational parameters. In summary, the outcomes from various systems of MXene and CNF-based nanocomposites demonstrate efficiency across different synthesis methods. We have explored diverse pathways for synthesizing nanostructured composite materials tailored for symmetrical supercapacitor applications. Notably, the MXene-assisted synthesis proved to be energy-efficient, exhibiting high performance and robust cycling stability. The combination of carbon nanofibers, MXenes, and metal oxides yielded a synergistic effect, leading to elevated specific capacitance, improved energy density, power density, and cycling stability.