Facile nano-templated CO2 conversion into highly interconnected hierarchical porous carbon for high-performance supercapacitor electrodes

Hierarchical porous carbon materials have been derived through CO2 conversion by using NaBH4 as a reducing agent and CaCO3 as a nano-template. The CaCO3-templated porous carbons (CPCs) feature an interconnected three-dimensional structure with hierarchical pores favorable for electrochemical energy storage. Notably, CPC1_700 prepared with an identical mass of CaCO3 and NaBH4 at 700 °C shows a very high capacitance of 270 F/g at 1 A/g and retains its capacitance up to 170 F/g at 20 A/g in 6 M KOH aqueous electrolyte. Moreover, it presents an outstanding normalized capacitance of 21.4 μF/cm2 even in the absence of pseudocapacitive behavior, and a fast frequency response with a low relaxation time constant of 0.27 s. Concerning the cycle stability, more than 90% of the initial capacitance is maintained after 10000 consecutive cycles at high current densities (20 A/g and 30 A/g). The major fundamental insights underlying this performance are closely related to the interconnected hierarchical pore architecture generated by the concurrent template and CO2 activation effect, which leads to increased surface area, fast ionic transport, and efficient ionic storage. The proposed route of CO2-to-carbon with the template affords a facile, efficient, and sustainable strategy to synthesize hierarchical porous carbon for high-performance supercapacitors.

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