Hierarchically Porous Carbon Nanosheets from One-Step Carbonization of Zinc Gluconate for High-Performance Supercapacitors.

Supercapacitors, with high energy density, rapid charge-discharge capabilities, and long cycling ability, have gained favor among many researchers. However, the universality of high-performance carbon-based electrodes is often constrained by their complex fabrication methods. In this study, the common industrial materials, zinc gluconate and ammonium chloride, are uniformly mixed and subjected to a one-step carbonization strategy to prepare three-dimensional hierarchical porous carbon materials with high specific surface area and suitable nitrogen doping. The results show that a specific capacitance of 221 F g-1 is achieved at a current density of 1 A g-1. The assembled symmetrical supercapacitor achieves a high energy density of 17 Wh kg-1, and after 50,000 cycles at a current density of 50 A g-1, it retains 82% of its initial capacitance. Moreover, the operating voltage window of the symmetrical device can be easily expanded to 2.5 V when using Et4NBF4 as the electrolyte, resulting in a maximum energy density of up to 153 Wh kg-1, and retaining 85.03% of the initial specific capacitance after 10,000 cycles. This method, using common industrial materials as raw materials, provides ideas for the simple preparation of high-performance carbon materials and also provides a promising method for the large-scale production of highly porous carbons.

Moss-Derived Mesoporous Carbon as Bi-Functional Electrode Materials for Lithium⁻Sulfur Batteries and Supercapacitors.

In this work, we reported a moss-derived biomass porous carbon (MPC) as a bi-functional electrode material for both the lithium⁻sulfur battery and the supercapacitor. The MPC was prepared from a high-temperature calcination procedure using the moss as the carbonaceous precursor. Using NaOH, the MPC was activated to give a mesoporous structure with a high specific surface area (1057.1 m² g-1) and large pore volume (0.72 cm³ g-1). When it was used as the cathode material in lithium⁻sulfur batteries, the MPC material realized a sulfur loading and exhibited a remarkably improved electrochemical performance, i.e., a high discharge capacity of 1070 mAh g-1 at 0.1 C. This activated MPC also worked well as a capacitive electrode in supercapacitors, demonstrating a high specific capacitance of 332 F g-1 (scan rate of 1.0 A g-1) and a high capacity retention > 97% in a long-term cycle of 1000 charge/discharges. This work demonstrated a facile method for the utilization of activated waste biomass material for future clean energy applications.