Synergistic catalytic graphitization and etching in molten salts enables high-performance wood-derived carbon electrodes for sustainable energy storage

Zinc-ion hybrid supercapacitors represent a promising energy storage technology, yet the scalable fabrication of carbon electrodes that simultaneously achieve high electrical conductivity and well-developed porosity remains a formidable challenge. Herein, we propose a one-step nickel-catalyzed molten salt strategy to fabricate self-supporting wood-derived carbon electrodes. Owing to the synergistic interplay of nickel catalysis and molten salt etching, catalytic graphitization and hierarchical pore formation are achieved concurrently at a relatively low temperature of 850 °C, thereby mitigating the limitations associated with conventional high-temperature graphitization (>2500 °C) and chemical activation methods. This synergy significantly enhances the degree of graphitization, as evidenced by a decrease in the Raman D/G intensity ratio (0.95–0.74) and a more pronounced (002) diffraction feature at 2 θ ≈ 25.8 o . Furthermore, the electrical conductivity is improved from 2.47 to 2.82 S cm −1 , accompanied by a substantially increased specific surface area from 872.9 ± 19.2 to 1222.2 ± 78.1 m 2 g −1 (approximately 183 times that of pristine wood-derived carbon, 6.65 ± 2.27 m 2 g −1 ), compared with the non-catalyzed molten salt-treated counterpart. Consequently, the optimized electrode delivers a high volumetric capacity of 17.30 mAh cm −3 at 2 mA cm −2 , which is 247 times that of pristine carbon (0.07 mAh cm −3 ), along with excellent rate capability and long-term cycling stability (80 % capacity retention after 16000 cycles), surpassing the non-catalyzed counterpart and many reported carbon-based electrodes. A prototype coin cell further validates its practical potential. This work provides a novel and sustainable paradigm for designing high-performance biomass-derived carbon materials.