High-energy plasma activation of renewable carbon for enhanced capacitive performance of supercapacitor electrode

High cost and environmentally unfavourable considerations are the major obstacles that prohibit renewable energy storage from many applications. To solve these issues, novel renewable materials such as biomass-derived carbon that have low cost, ecofriendly, and deliver high-energy storage performance should be employed. In this work, renewable carbon YP-50, biochar synthesized from coconut, was activated using different plasma gases including methane (CH₄), carbon dioxide (CO₂), hydrogen (H₂), and argon (Ar). Compared with the conventional activation method, plasma treatment takes less time and effort. A significant increase in the specific surface area (SSA) and improvement in the specific capacitance (SC) were found with different plasma treatments. Specifically, the CH₄ plasma-treated YP-50 exhibited the highest SC of 181.6 F g⁻¹ at 0.05 A g⁻¹ compared with other gases. In addition, the highest energy density of 25.3 Wh kg⁻¹ was obtained at the specific power of 0.12 kW kg⁻¹ for CH₄ treated biochar. This enhancement of charge storage capacity is highly associated with the distribution of a variety of pore sizes and a large surface area. Furthermore, the charge transfer resistance reduced from 21.7 Ω to 1.4 Ω after CH₄ treatment, and high capacitance retention was achieved due to its excellent electrochemical stability and good performance. Hence, this high-energy plasma treatment with a short time opens p a new opportunity for the efficient activation of carbon materials of supercapacitors with high electrochemical performances.