The Role of Biochar Concentration on the Structure and Electrical Performance of MnO2-Biochar Composite Electrodes for Supercapacitor Applications.

T. Sadowski, M. Martone, V. Adamski, A. Grynyk, K. Roman, J. Scanley, R. Singhal, C. Broadbridge
Southern CT State University,
United States

Keywords: supercapacitors, BioChar, composite electrodes, sustainable nanotechnology


The demand to diversify the global energy portfolio to include more renewable sources has illustrated an acute and critical need for advancements in energy storage technology to mediate their inherent intermittent nature. Hybrid supercapacitors offer such a solution for a wide range of commercial and infrastructural energy applications, with great potential for fabrication utilizing cost-effective and environmentally benign materials. In particular, electrodes composed of biochar alongside MnO2 (for electric double-layer and pseudocapacitance charge storage mechanisms, respectively) are seen as great potential candidates that fit this sustainability-driven profile. In a previous study, a flexible, one-pot synthesis method was used to fabricate MnO2, biochar, and MnO2-biochar electrodes. Characterization indicates that nanocrystalline δ-MnO2 is synthesized that largely mixes with the microporous biochar to create a composite with varying levels of homogeneity. The specific capacitance of these MnO2-biochar composites were measured to be lower than MnO2-carbon nanotube (CNT) hybrid electrodes that were prepared under optimized conditions resulting in a greater degree of structural uniformity. It follows that there exists ample opportunity to optimize the MnO2-Biochar composite through physical and/or chemical modifications of the biochar as well as optimization of the initial concentration. In this study, the performance of pine-based biochar-MnO2 hybrid electrodes of varying biochar concentrations, synthesized using the same one-pot method, were investigated. Motivated by our previous work with CNT, the initial biochar concentrations were chosen to be 25-mg, 50-mg, 75-mg, and 100-mg. The electrode surface area was quantified by BET surface analysis and the structure and composition using x-ray diffraction. The supercapacitive performances were investigated using cyclic voltammetry ranging from 3-200 mV s-1 as well as galvanostatic charge-discharge tests at 0.5, 1.0, and 2.0 A/g. This data, along with scanning and transmission electron microscopy data, provide insight on the structure-property-performance relationship for these composite material systems. Furthermore, preliminary findings on the impact of processing and surface modification of biochar will be presented.