Hierarchical macro-/meso-/microporous oxygen-doped carbon derived from sodium alginate: A cost-effective biomass material for binder-free supercapacitors

Three-dimensional porous scaffolds doped with the heteroatoms show excellent performances in energy conversion and storage. Herein, we report a green synthesis approach to construct the oxygen-doped porous carbon electrodes by carbonizing the oxygen-rich biomass material, sodium alginate. By precisely controlling the carbonization temperature and increasing the mole ratio of α-L-guluronic acid units/β-D-mannuronic acid units in sodium alginate, the morphology, oxygen content and electrical conductivity of the as-obtained carbonaceous electrode are well balanced. This electrode material delivers capacitance of up to 424.6 F g−1 in 6 M potassium hydroxide (KOH) electrolyte at 1 A g−1, and good cyclic stability with the capacitance retention of >90% after 20,000 charge-discharge cycles. Such excellent electrochemical performance can be attributed to both the unique hierarchical macro-/meso-/microporous structure and the presence of abundant oxygen-containing functional groups in the as-prepared carbonized sodium alginate aerogels. The capacitance of our oxygen-doped porous carbon electrodes is at least twice greater than those of other carbonaceous electrodes produced from biomass precursors reported in literatures. This work provides a facile, effective and environmental-friendly approach for the fabrication of high-performance heteroatom-doped carbon-based electrodes for supercapacitor applications.