Harnessing Seaweed-Derived Multiporous Activated Carbon for High-Performance Energy Storage and Water Splitting Applications

The development of sustainable, high-performance materials for integrated energy storage and conversion is essential to address rising energy demand and safeguard the environment. This study demonstrates the strategic use of seaweed-derived activated carbon (SWAC), leveraging its intrinsic nitrogen-rich composition to produce a heteroatom-doped multiporous structure suitable for both electrochemical energy storage and water electrolysis applications. Using a straightforward activation and functionalization process, we synthesized nitrogen-enriched SWAC exhibiting a large surface area and cross-linked pore structure. The material showed favorable performance in both electrochemical energy storage and conversion applications. The optimized activated carbon achieved a remarkable specific capacitance of up to 549.7 F g⁻1 in a three-electrode setup and maintained 224.2 F g⁻1 at 1.0 A g⁻1 in a symmetrical supercapacitor device with excellent long-term cycling stability as high as 94% after 18,000 cycles. Furthermore, the SWAC-800 electrode (calcined at 800 ℃) showed strong bifunctional metal-free electrocatalytic performance with low hydrogen evolution reaction (HER) overpotentials of 170 and 268 mV, and oxygen evolution reaction (OER) overpotentials of 315 and 373 mV at current densities of 10 and 100 mA cm⁻2, respectively. The chronopotentiometric stability was maintained for 50 h at 50 mA cm⁻2. These results not only validate seaweed as a highly effective biomass precursor but also position the resulting material as a versatile, eco-friendly electrocatalyst for next-generation supercapacitors and green hydrogen production systems.