An innovative method has been introduced to transform used oil into a high-value material with tailored properties for supercapacitor electrodes
New Advances in Supercapacitor Materials
Improving the production of base materials for supercapacitors by “mining” waste—this is the approach adopted by a research team from Shanghai University and Tongji University. The team successfully obtained high-quality porous carbon, essential for electrodes, from used oil.
The field of research is energy storage, where supercapacitors, known for their fast charge/discharge speeds and longer cycle life than batteries, are positioning themselves as essential components.
“However,” writes the Chinese Academy of Sciences, “to meet the growing demand, supercapacitors require high-quality electrode materials that balance conductivity with a large surface area—an area in which many conventional compounds are deficient.”
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The Importance of Hierarchical Porous Carbon
These energy storage devices use the surface area of the electrode to store energy via electrostatic adsorption. Specific materials like hierarchical porous carbon (HPC), carbon fiber, carbon nanotubes, or graphene are used for this task.
Among them, HPC has attracted significant attention for its high number of multi-scale pores (macro-, meso-, and micro-), which can serve as “ionic buffering reservoirs” to shorten ion diffusion paths or as fast transport channels for the same ions.
Various methods have been used to prepare hierarchical porous carbon, but most of the processes are long, complex, and challenging. Chinese scientists have studied advanced carbon materials with intricate porous structures and strategically positioned nitrogen atoms, a process known as heteroatom doping.
Supercapacitors with Nitrogen-Doped HPC Electrodes
The research team specifically chose linoleic acid (found in used oils) and melamine as sources of carbon and nitrogen, respectively. After heating the materials to 600°C and treating them with potassium hydroxide, the researchers produced HPC with an impressive surface area of up to 3474.1 m²/g.
This carbon has 72.9-77.3% mesopores in its structure, which are essential for enhancing the supercapacitor’s storage capacity and ion transport efficiency. In this context, nitrogen doping, facilitated by melamine, improves conductivity and introduces active sites within the carbon structure, increasing electrochemical reactivity.
As a result, the material achieved a specific capacity of 430.2 F/g, with an 86.5% retention rate after 2,000 charge/discharge cycles. The study’s findings were published in Waste Disposal & Sustainable Energy.
