Inspired by the spongy bone structures, three-dimensional (3D) sponge-like carbons with meso-microporous structures are synthesized through one-step electro-reduction of CO2 in molten carbonate Li2 CO3 -Na2 CO3 -K2 CO3 at 580 °C. SPC4-0.5 (spongy porous carbon obtained by electrolysis of CO2 at 4 A for 0.5 h) is synthesized with the current efficiency of 96.9 %. SPC4-0.5 possesses large electrolyte ion accessible surface area, excellent wettability and electronical conductivity, ensuring the fast and effective mass and charge transfer, which make it an advcanced supercapacitor electrode material. SPC4-0.5 exhibits a specific capacitance as high as 373.7 F g-1 at 0.5 A g-1 , excellent cycling stability (retaining 95.9 % of the initial capacitance after 10000 cycles at 10 A g-1 ), as well as high energy density. The applications of SPC4-0.5 in quasi-solid-state symmetric supercapacitor and all-solid-state flexible devices for energy storage and wearable piezoelectric sensor are investigated. Both devices show considerable capacitive performances. This work not only presents a controllable and facile synthetic route for the porous carbons but also provides a promising way for effective carbon reduction and green energy production.
Keywords: CO2 capture and conversion; electrochemical reduction; molten salts; spongy meso-microporous carbon; supercapacitor.
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