Key Takeaways & Executive Findings
- •• Joule heating technique (JHT) enables ultra-fast preparation of porous carbon with a heating rate of 1100 K/s, significantly reducing time and energy consumption compared to traditional furnace methods. • The resulting porous carbon exhibits a high specific surface area of 1652.7 m2/g and an excellent specific capacitance of 476.0 F/g in aqueous alkaline electrolyte, with 75.1% capacitance retention at 64.0 A/g. • Symmetric supercapacitors using this carbon achieve maximum energy densities of 33.3 Wh/kg (water-in-salt) and 50.8 Wh/kg (organic electrolyte), with high power densities and excellent cycling stability (93.1% retention after 10,000 cycles in water-in-salt). • JHT allows precise control of pyrolysis, enabling tailored pore structures and properties, positioning it as a promising ultra-fast method for energy storage materials.
Abstract
The typical method for preparing the porous carbon used in supercapacitors (SCs) is time-consuming and energy-intensive. We report a fast and efficient route to synthesize and tailor the structure of porous carbon by a Joule heating technique (JHT) using phenolic resin and precursors. During the JHT process, the time and energy needed are both significantly reduced because the precursor is heated to the target temperature at a rate of 1100 K/s, so the porous carbon is formed with the release of small molecules and the etching of the substrate by K2CO3. JHT has a higher energy efficiency than traditional carbonization methods in a tube furnace and allows for precise control of the pyrolysis process, thus achieving better control of the material's structure and properties. Samples obtained by JHT contain abundant pores and a large specific surface area (1652.7 m2/g), which give an excellent specific capacitance of 476.0 F/g and rate capability (75.1% capacitance retention at 64.0 A/g in an aqueous alkaline electrolyte). Furthermore, in electrolytes of 17.0 mol/kg NaClO4 (water-in-salt) and 1.0 mol/L TEABF4/AN, the symmetric SCs have a maximum energy density of 33.3 and 50.8 Wh/kg at power densities of 220.4 and 376.4 W/kg, respectively. The cells also have good long-term stability, with a nearly 100% Coulombic efficiency, and a capacitance retention of 93.1% in a water-in-salt electrolyte after 10000 cycles, and 88.9% in an organic electrolyte after 8000 cycles. This study shows that JHT has the potential to serve as an ultra-fast method to prepare porous carbons for energy storage.
1. Introduction
Along with the continuous development on new sources of energy, building more efficient energy storage devices is attracting more research interest[1–6]. Among various types of energy storage devices, supercapacitors (SCs) have obtained considerable attention due to their high power density, low cost, and long lifecycle[7–8]. It is proven that the performance of SCs is primarily dependent on their electrode materials’ properties[9–10]. Among all the possible electrode materials, porous carbon is considered the most promising due to its high conductivity, stability, and regulatable pore structure. It is found that the performance of porous carbon materials are strongly dependent on the selection of precursors and the parameters of optimization during the preparation process[11–13]. Phenolic resin is particularly suitable precursor for preparing porous carbon materials because of its simple preparation process, high yield and controllable structure[14–17]. By tuning the composition, specific surface area (SSA) and pore size distribution (PSD), the performance of carbon materials in energy storage devices can be significantly enhanced[18].
Currently, hierarchical porous carbon materials are considered as the most promising electrode materials for energy storage because they possess macropores, mesopores, and micropores simultaneously. Therefore, various new methods have been published in search of the optimal fabrication method for hierarchical porous carbon materials with high porosity and well developed pore structures[19–21]. Up until now, using a high temperature environment to activate the primitive carbon is generally beneficial for the performance of the final product[22–24], but it comes at the expense of longer process and higher energy use. By using traditional heating in resistance furnaces, porous carbon materials are prepared through a two-step process: carbonization and activation under inert atmosphere. By using lignin based phenolic resin as a raw material, Peng et al.[25] have prepared porous carbon via carbonizing the precursor in a muffle furnace and activating it in a tube furnace a
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JIA Ya-jun, HAN Zi-yue, LIU Hui-chao, CHANG Yun-zhen, ZHU Sheng, HOU Wen-jing, LIU Shu-jie, ZHANG Ying, ZHANG Jin-jiao, HAN Gao-yi (2025). The rapid preparation of porous carbon with an improved capacitance. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2025-6-3)
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
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Frequently Asked Questions
What is the Joule heating technique (JHT) for preparing porous carbon?
JHT is an ultra-fast method that heats precursors to target temperatures at rates up to 1100 K/s, significantly reducing time and energy consumption compared to traditional furnace-based carbonization. It enables precise control of pyrolysis, leading to tailored pore structures and improved capacitive performance.
What are the key performance metrics of the porous carbon prepared by JHT?
The porous carbon exhibits a specific surface area of 1652.7 m2/g, a specific capacitance of 476.0 F/g in aqueous alkaline electrolyte, and 75.1% capacitance retention at 64.0 A/g. In symmetric supercapacitors, it achieves energy densities of 33.3 Wh/kg (water-in-salt) and 50.8 Wh/kg (organic electrolyte).
How does JHT compare to traditional carbonization methods?
JHT offers higher energy efficiency and faster processing times, with heating rates of 1100 K/s, while allowing precise control over the pyrolysis process. This results in better control of the material's structure and properties compared to conventional tube furnace methods.
What are the long-term stability and cycling performance of the supercapacitors?
The symmetric supercapacitors show nearly 100% Coulombic efficiency and capacitance retention of 93.1% after 10,000 cycles in water-in-salt electrolyte, and 88.9% after 8,000 cycles in organic electrolyte, indicating excellent long-term stability.
What precursors are used in this study?
The study uses phenolic resin as the carbon precursor, along with K2CO3 as an activating agent. The JHT process involves heating the precursor to release small molecules and etch the substrate to form porous carbon.
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