Aabha Puri graduated with a master's degree from Tribhuvan University in Nepal. She is currently a second-year PhD student at the University of Tsukuba and a Junior Researcher at the National Institute for Materials Science (NIMS), Japan. Her research focuses on engineering porous carbon materials for energy storage applications. Her broader research interests lie in developing scalable, environmentally friendly materials for next-generation energy technologies.

The rapid growth of the global economy has intensified fossil fuel consumption, leading to resource depletion and environmental concerns, thereby accelerating the demand for renewable energy systems and efficient energy storage technologies. Supercapacitors are promising energy storage devices due to their high-power density, rapid charge–discharge capability, long cycle life, and excellent rate performance; however, their relatively low energy density remains a critical limitation [1,2]. To address this challenge, the rational design of sustainable, high-performance electrode materials via simple, scalable synthesis strategies is essential [3]. Herein, we report the fabrication of high-surface-area, self-heteroatom-doped hierarchical porous carbon from the sustainable biomass precursor, Achyranthus bidentata. The porosity can be freely controlled by tuning the carbonization temperature, the type of activator, and the impregnation ratios [4,5]. The optimized sample exhibits an ultra-high surface area of 2251 m² g⁻¹ with partial graphitization and retained surface heteroatoms, which contribute to enhanced electrochemical activity. The sample exhibits good electrochemical performance, with a specific capacitance of 266 F g-1 at 1 A g-1 and excellent rate capability in a three-electrode cell. The hybrid cell constructed by integrating this sample with binary Ni-Co selenide delivered a high energy density of 28 Wh kg-1 at a power density of 424 W kg-1, along with good rate capability, decent cyclic stability, and a remarkable coulombic efficiency over 5000 cycles. The synergistic strategy of engineering porous carbon and hybrid device design greatly enhanced the electrochemical performance of a supercapacitor. Hence, this work demonstrates that biomass serves as an excellent precursor for the fabrication of porous carbon materials, highlighting their potential as sustainable, promising electrode materials for future advanced energy storage applications.

1. W. Li, X. Yang, Z. Chen, T. Lv, X. Wang, J. Qiu, Carbon 196, 136-145 (2022), https://doi.org/10.1016/j.carbon.2022.04.037
2. Y. Sun, X. L. Shi, Y. L. Yang, G. Suo, L. Zhang, S. Lu, Z. G. Chen, Adv. Funct. Mater 32, 2201584 (2022), https://doi.org/10.1002/adfm.202201584
3. N. Pravin, D. Merum, M. Kang, S. W. Joo, T. K. Mandal, J. Mater. Chem. A 13, 24320-24386 (2025), https://doi.org/10.1039/D5TA02887F
4. S. Manandhar, S. Shahi, C. L. Gnawali, K. Ariga, L. K. Shrestha, J. Power Sources 689, 240759 (2026), https://doi.org/10.1016/j.jpowsour.2026.240759
5. S. Shahi, S. Manandhar, R. G. Shrestha, C. L. Gnawali, M. P. Adhikari, K. Ariga, L. K. Shrestha, Bull. Chem. Soc. Jpn 99(8), uoag096 (2026), https://doi.org/10.1093/bulcsj/uoag096