Porous carbon foams prepared by CaCl2 molten salt assisted carbonization for supercapacitors

Porous carbon materials are widely used as electrode materials for supercapacitors due to their tunable structure and stability. Here, using sodium carboxymethyl cellulose (CMC-Na) as the carbon precursor, porous carbon foams with intrinsic oxygen were successfully constructed through a one-step calcium chloride (CaCl 2 ) molten salt system assisted carbonization and activation strategy. During this process, the oxygen in CMC-Na is partially retained in situ while CaCl 2 not only acts as an activator to promote mesoporous structure development but also guides the formation of stable hierarchical pore structure through ion exchange effect. The optimal sample (C-5–900) exhibits an oxygen content of 4.6 at% and a specific surface area of 722 m 2 g −1 , demonstrating effective in situ oxygen retention and porous architecture. In a three-electrode system, this material achieved a specific capacitance of 172 F g −1 at a current density of 0.1 A g −1 in 6 M KOH electrolyte. Symmetrical supercapacitors (C-5–900//C-5–900) maintained 99.0 % and 89.5 % capacitance retention after 20,000 and 60,000 cycles at a high current of 30 A g −1 , demonstrating outstanding electrochemical stability. Notably, the device capacitance performance further improved with KI addition in electrolyte. This work provides a valuable synthetic pathway and performance reference for the controllable preparation of porous carbon materials and their application in high-efficiency energy storage devices.