Characterization of activated biomass carbon from tea leaf for supercapacitor applications

Dielectric barrier discharge low-temperature plasma modification of bamboo charcoal for supercapacitor applications

Biochar is commonly utilized as an electrode material in supercapacitors. However, the conventional carbonization process often results in macromolecular compounds, which obstruct the porous structure of carbon materials, thereby reducing their capacitance. Dielectric barrier discharge low-temperature plasma (DLTP) is a technology that transforms gases into highly excited states, utilizing high-energy particles for enhanced energy applications. This study investigated the effects of DLTP on the electrochemical performance of bamboo charcoal (BC), utilizing bamboo shavings (BS) as the carbon source. The results indicated that the specific capacitance of BC varied under different atmospheric conditions, input voltages, and treatment durations, thereby achieving a maximum increase of 144 F/g. Furthermore, when combined with KOH activation, DLTP modification further enhanced the specific capacitance of BC to 237 F/g. The DLTP treatment enhanced the specific surface area and the types of functional groups in BC, thereby leading to a significant enhancement of its electrochemical properties.

Supercritical-CO2 mediated preparation of porous carbon from Araucaria heterophylla biomass: A proficient nanomolar detection platform for phenolic water pollutant

4-aminophenol (AP), an aromatic phenolic compound, is commonly found in commercial products that eventually enter and pollute environmental water sources. The precise detection and quantification of AP in environmental samples are critical for comprehensively assessing contamination levels, safeguarding public health, and formulating effective remediation strategies. In the shed of light, this work proposes an electrochemical sensing platform for detecting and quantifying AP using Araucaria heterophylla biomass-derived activated carbon (AH-AC) prepared via the SC-CO2 pathway. To evaluate the significance of SC-CO2-mediated chemical activation (SC-AHAC), a comparative study with conventional activation methods (C-AHAC) was also conducted. The physical characterizations such as structural, morphological, optical, and elemental analysis demonstrate the greater ID/IG value and enhanced surface functionalities of SC-AHAC than C-AHAC. The obtained lower empirical factor (R) value of 1.89 for SC-AHAC suggests increased disorder and a higher presence of single-layer amorphous carbon compared to C-AHAC (2.03). In the electrochemical analysis, the active surface area of the SC-AHAC modified electrode (0.069 cm2) is higher than that of the C-AHAC modified electrode (0.061 cm2), demonstrating the significance of SC-CO2 activation. Further, the quantitative analysis on SC-AHAC@SPCE resulted in a sensitivity of 3.225 μA μM-1 cm-2 with the detection limit and quantification limit of 2.13 and 7.11 nM L-1, respectively, in the linear range of 0.01-582.5 μM L-1 at the oxidation potential of 0.13V. This suggests that the prepared SC-AHAC could be a promising electrocatalyst for AP detection in the environmental and healthcare sectors.

Sweet Side Streams: Sugar Beet Pulp as Source for High-Performance Supercapacitor Electrodes

Valorization of the lignocellulosic side and waste streams is key to making industrial processes more efficient from both an economic and ecological perspective. Currently, the production of sugars from beets results in pulps in large quantities. However, there is a lack of promising opportunities for upcycling these materials despite their promising properties. Here, we investigate beet pulps from two different stages of the sugar manufacturing process as raw materials for supercapacitor electrodes. We demonstrate that these materials can be efficiently converted to activated, highly porous carbons. The carbons exhibit pore dimensions approaching the size of the desolvated K+ and SO42- ions with surface areas up to 2600 m2 g-1. These carbons were subsequently manufactured into electrodes, assembled in supercapacitors, and tested with environmentally friendly aqueous electrolytes (6 M KOH and 1 M H2SO4). Further analysis demonstrated the presence of capacitance-enhancing functionalities, and up to 193 and 177 F g-1 in H2SO4 and KOH, respectively, were achieved, which outperformed supercapacitors prepared from commercial YP80 F. Overall, our study suggests that side streams from sugar manufacturing offer a hidden potential for use in high-performance energy storage devices.

Renewable Carbon Materials as Electrodes for High-Performance Supercapacitors: From Marine Biowaste to High Specific Surface Area Porous Biocarbons

Waste, in particular, biowaste, can be a valuable source of novel carbon materials. Renewable carbon materials, such as biomass-derived carbons, have gained significant attention recently as potential electrode materials for various electrochemical devices, including batteries and supercapacitors. The importance of renewable carbon materials as electrodes can be attributed to their sustainability, low cost, high purity, high surface area, and tailored properties. Fish waste recovered from the fish processing industry can be used for energy applications and prioritizing the circular economy principles. Herein, a method is proposed to prepare a high surface area biocarbon from glycogen extracted from mussel cooking wastewater. The biocarbon materials were characterized using a Brunauer-Emmett-Teller surface area analyzer to determine the specific surface area and pore size and by scanning electron microscopy coupled with energy-dispersive X-ray analysis, Raman analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrochemical characterization was performed using a three-electrode system, utilizing a choline chloride-based deep eutectic solvent (DES) as an eco-friendly and sustainable electrolyte. Optimal time and temperature allowed the preparation of glycogen-based carbon materials, with a specific surface area of 1526 m² g^-1, a pore volume of 0.38 cm³ g^-1, and an associated specific capacitance of 657 F g^-1 at a current density of 1 A g^-1, at 30 °C. The optimal material was scaled up to a two-electrode supercapacitor using a DES-based solid-state electrolyte (SSE@DES). This prototype delivered a maximum capacitance of 703 F g^-1 at a 1 A g^-1 of current density, showing 75% capacitance retention over 1000 cycles, delivering the highest energy density of 0.335 W h kg^-1 and power density of 1341 W kg^-1. Marine waste can be a sustainable source for producing nanoporous carbon materials to be incorporated as electrode materials in energy storage devices.

Hollow CoS2 anchored on hierarchically porous carbon derived from Pien Tze Huang for high-performance supercapacitors

The development of electrode materials with a high specific capacitance, power density, and long-term stability is essential and remains a challenge for developing supercapacitors. Cobalt sulfides (CoS₂) are considered one of the most promising and widely studied electrode materials for supercapacitors. Herein, CoS₂ and hierarchical porous carbon derived from Pien Tze Huang waste are assembled into a cobalt sulfide/carbon (CoS₂/PZH) matrix composite using a one-step hydrothermal method to resolve the challenges of supercapacitors. The resulting CoS₂/PZH composite material exhibits a hierarchical porous structure with hollow CoS₂ embedded in a PZH framework. The uniform dispersion of the hierarchical porous structure CoS₂/PZH is achieved due to the PZH framework, while the uniform decoration of the porous PZH with the hollow CoS₂ prevents the PZH from stacking easily. Moreover, the excellent synergistic effect of the hierarchical porous and hollow structure of CoS₂/PZH can shorten the electron/ion diffusion channels, expose additional active sites, and provide stable structures for subsequent reactions. As a result, the CoS₂/PZH composite material displays a high initial specific capacity of 447.5 F g^-1 at 0.5 A g^-1, a high energy density of 22.38 W h kg^-1, and long-term cycling stability (a retention rate of 92.3% over 10 000 cycles at 5 A g^-1).

A Simple Route to Produce Highly Efficient Porous Carbons Recycled from Tea Waste for High-Performance Symmetric Supercapacitor Electrodes

High-performance porous carbons derived from tea waste were prepared by hydrothermal treatment, combined together with KOH activation. The heat-treatment-processed materials possess an abundant hierarchical structure, with a large specific surface of 2235 m² g⁻¹ and wetting-complemental hydrophilicity for electrolytes. In a two-electrode system, the porous carbon electrodes’ built-in supercapacitor exhibited a high specific capacitance of 256 F g⁻¹ at 0.05 A g⁻¹, an excellent capacitance retention of 95.4% after 10,000 cycles, and a low leakage current of 0.014 mA. In our work, the collective results present that the precursor crafted from the tea waste can be a promising strategy to prepare valuable electrodes for high-performance supercapacitors, which offers a practical strategy to recycle biowastes into manufactured materials in energy storage applications.