Sodium alginate-derived porous carbon: Self-template carbonization mechanism and application in capacitive energy storage

Sodium alginate (SA) is an environment-friendly and low-cost polysaccharide carbohydrate extracted from seaweed. As a carbon precursor, sodium alginate has the advantages of clear molecular structure, small molecular weight, and easy controls of the structure and composition of the product, but there have been few studies for the mechanism for SA carbonization. In this work, the carbon skeleton cross-linking mode, heteroatom doping and defect generation mechanism in the process of SA pyrolysis are clarified. Subsequently, based on the understanding of the carbonization mechanism of SA-derived carbon, we have prepared a stable SA-derived interconnected porous carbon by self-template method. The materials prepared by this method possess high oxygen content (17.6 at%) and high specific surface area (384.4 m2 g-1). Zn-ion hybrid capacitors (ZICs) device assembled with SA-derived porous carbon performs superior energy densities (based on cathode mass) of 78.35 and 35.56 Wh kg-1 at the power densities of 160 and 5120 W kg-1, respectively. This work deeply explained the carbonization mechanism of sodium alginate and evaluated the application prospects of SA-based carbon in ZICs comprehensively.