Energy storage for sustainable development and progress of power production industries is vitally important. The energy storage devices are under extensive research from last three decades to ensure the hand-on-hand coordination with power supply phenomenon and to reduce the energy loses in lines. The cost-effective materials are still highly demanding as an electrode material for energy storage devices. Biomass-derived carbon materials are best candidates due to their low cost, relatively high abundance, pollution-free nature. Here, we are reporting a facile two-step green approach to convert Himalayan horse chestnuts (HHCNs) into activated carbon materials. In first step, grinding and pyrolysis of the HHCNs were carried out, and then activation was performed using KOH to enhance the pore density and surface area. HHCNs-derived carbon was utilized as an electrode in electrical double-layer capacitors (EDLCs) with 1 M H2SO4 as an electrolyte. The macroporous structure along with hierarchical porous network acts as an efficient source of transportation of charges across the electrode and separator. Cyclic voltammetry test was taken from 10 to 100 mV/s current and within a range of 0–1 V applied potential; approximately rectangular CV shown mirror response towards current and shown typical EDLCs properties. The proximate analysis confirms the presence of heteroatoms like sulfur, oxygen, and nitrogen which act as carbon dopants. The wettability of HHCNs-derived carbon enhanced due to the various types of oxygen functionalities inherited from the lignin skeletal part. The nitrogen content is primarily responsible for the pseudo-capacitive behavior of HHCNs-codoped carbon. HHCNs-derived activated carbon materials has emerged as a promising electrode material for energy storage applications.

In recent years, supercapacitors have attracted extensive attention due to their advantages such as fast charge and discharge rate, high power density and long cycle life. Because of its unique porous structure and excellent electrochemical properties, heteroatom-doped porous carbon (HPC) is deemed as a promising electrode material for supercapacitors. However, it is a great challenge to synthesize electrode materials with large surface area, ultra-high porosity and good electrochemical performance. In this work, two-dimensional conjugated microporous polymers (CMPs) containing ketones were synthesized by a simple one-step coupling reaction and used as carbon precursors. A series of samples (CMP-Ts) were prepared with the procedures of coupling reaction and carbonization. The optimized carbon material has high specific surface area (up to 2229.85 m2 g− 1), porous structure, high specific capacitance (375 F g− 1 at 0.5 A g− 1), and good cycling stability (capacitance retention of 98.8% after 1000 cycles at 5 A g− 1). Further, the supercapacitor has an energy density of 28.8 Wh kg− 1 at a power density of 5000 W kg− 1. This work lays a foundation for the preparation of carbon materials using microporous polymer as a precursor system, provides a new way of thinking, and demonstrates a great potential of high-performance supercapacitors.

In this report, we successfully prepared nitrogen-doped porous carbon (N-PC)/manganese dioxide ( MnO2) composite for a high-performance supercapacitor. X-ray diffraction data revealed the α-MnO2 phase. Transmission electron microscopy confirmed that the nanostructured α-MnO2 nanoparticles were coated on the surface of N-PC. The N-PC/α-MnO2 composite delivered a capacitance of 525.7 F g− 1 at the charging current of 1.0 A g− 1. The higher capacitance of the composite could be owing to the synergy of MnO2 and N-PC. Besides, the electrode exhibited a 14.7% capacitance loss after 6000 charge– discharge cycles at 10 A g− 1 indicating good electrochemical stability.