Three-dimensional hierarchical porous carbon aerogel from sodium alginate by NaCl molten salt-enhanced K2CO3 activation for supercapacitor electrodes

The hierarchical porous carbon aerogels were prepared by dual molten salt method. • The symmetrical supercapacitor obtains 7.7 Wh·kg −1 at 60.0 W·kg −1 . • The symmetrical supercapacitor retains 96.23% capacity after 10,000 cycles. To boost the actual specific capacity and low rate performance of supercapacitors, it is necessary to effectively modulate storage sites of porous carbon materials, including microscopic defects and pore structures. In this study, a three-dimensional hierarchical porous carbon aerogel (KCA-0.5-0.5-800) was fabricated using sodium alginate as a biomass precursor via a synergistic activation strategy combining molten NaCl template and K 2 CO 3 chemical activation. The prepared material possesses an ultra-high specific surface area of 1908.4 m 2 ·g −1 and a large pore volume of 1.188 cm 3 ·g −1 , featuring a well-interconnected micro-meso-macroporous network and abundant structural defects. The KCA-0.5-0.5-800 electrode delivers a prominent specific capacitance of 286.4 F·g −1 at 0.5 A·g −1 in a three-electrode system, and maintains a capacitance retention of 72.11% at 5 A·g −1 . The assembled symmetric supercapacitor achieves a high energy density of 7.7 Wh·kg −1 at a power density of 60.0 W·kg −1 . Moreover, the device retains 96.23% of its initial capacitance along with a nearly 99.99% coulombic efficiency after 10 000 consecutive charge–discharge cycles at 5 A·g −1 . The prepared carbon aerogel showcases promising application prospects due to its unique structural features and outstanding electrochemical performance. Download: Download high-res image (175KB) Download: Download full-size image