Hierarchically porous carbon from foamed Mg chelate for supercapacitor and capacitive deionization

Pore hierarchy facilitates the mass transportation/exchange between the interior surface and bulk solution, which is critical for the enhancement of capacitive performance. Herein, by applying in situ foamed Mg chelates as precursors, we managed the scalable fabrication of hierarchically porous carbon (HPC) materials and explored their capacitive applications. Particularly, citric acid first reacted with magnesium nitrate to form Mg chelate while the generated gaseous HNO 3 molecules bubbled the intermediate carbon framework to produce abundant open pores. The as-made precursors were then submitted to potassium hydroxide activation for a high carbonization degree and rich meso-/micropores. The optimized sample (HPC-2) exhibited very high specific capacitance of 213.5 F g −1 in neutral NaCl solution and a high rate capability of ~ 67.5% at 10.0 A g −1 . Furthermore, it showed impressive capacitive deionization performance regarding high removal efficiency (67.1%), large capacity of 1810.1 mg g −1 (in 2200 mg L −1 NaCl solution), and robust cycling stability.