The Energy storage devices (ESDs) like batteries, supercapacitors (SCs), fuel cells, etc., are the hefty fragments playing their role in technological advancements and dwindling dependency on fossil fuels. They have been investigated predominantly and are the prime focus of research in the last three decades to improve their performance. Among these ESDs, SCs, particularly carbon-based electric double-layer capacitors (EDLCs), have gained enormous attention from researchers and commercial firms. In this regard, graphitic carbons taking advantages of their high conductivity values have gained enormous attention recently. Graphitic carbon materials along with high surface area and hierarchical pore structures are the desired materials for enhanced EDLC application.

Here, we have synthesized novel graphitic carbon material with dual porosity inherited from zeolitic imidazolate framework (ZIF-67) and polystyrene. We have used room temperature precipitation method followed by carbonization to achieve these structures. The composite material then washed with 10% HF solution for removing unreacted metal particles. The porous carbon network as shown in the Figure 1 (a) and (b), displays the macropore of about 500 nm formed due to the extraction of polystyrene particle. The boundaries and the base of these pores is formed up by the porous carbon particle extracted from the ZIF-67 network. In this way, the composite material exhibited excellent porosity and surface area values. The adsorption-desorption isotherms are displayed in Figure 1 (c), showing the material exhibits type-I isotherm. The BET surface area is calculated to be 337 m²/g. The pore size distribution is calculated using NLDFT model as shown in Figure 1 (d). In addition to these, various structural characterization including powder XRD, XPS, FT-iR and EDS has been performed for the synthesized material. As per the XRD and XPS studies, it is confirmed that the sample is having good graphitic degree.

The material is utilized to use as the active material for SC application. For preparing electrode, firstly the slurry was prepared by mixing composite material with 10% polyvinylidene fluoride in N-Methyl pyrrolidone solution. This mixture is then drop casted on the graphite substrate and kept for drying at 80 ºC overnight. We have used three electrode configuration for testing SC performance of composite material. The cyclic voltammetry (CV) profiles in 3M KOH solutions at different scan rates are being portrayed in Figure 1 (e). The composite material exhibited typical rectangular CV shape as expected. The capacitance values at different scan rate is shown in Figure 1 (f), displaying excellent capacitive behavior. This excellent performance is due to the bimodal porosity of the material. The micropores helps in increased capacitance by storing more charges, while the meso and micropores helps in maintaining the charge storage at high scan rates. Further, the composite material is tested for symmetric supercapacitor device and exhibited excellent energy and powder density values. The assembled coin cell exhibited highest 16.6 Wh/kg energy density and 12000 W/kg power density. These excellent performance metrices shows the materials potential for not only supercapacitor electrode material but also for various metal ion capacitors and batteries. This study provides the initial findings of novel composite material for supercapacitor application.