Digested sludge-derived three-dimensional hierarchical porous carbon for high-performance supercapacitor electrode.

Digested sludge, as the main by-product of the sewage sludge anaerobic digestion process, still contains considerable organic compounds. In this protocol, we report a facile method for preparing digested sludge-derived self-doped porous carbon material for high-performance supercapacitor electrodes via a sustainable pyrolysis/activation process. The obtained digested sludge-derived carbon material (HPDSC) exhibits versatile O-, N-doped hierarchical porous framework, high specific surface area (2103.6 m ²  g ^-1 ) and partial graphitization phase, which can facilitate ion transport, provide more storage sites for electrolyte ions and enhance the conductivity of active electrode materials. The HPDSC-based supercapacitor electrodes show favourable energy storage performance, with a specific capacitance of 245 F g ^-1 at 1.0 A g ^-1 in 0.5 M Na ₂ SO ₄ ; outstanding cycling stability, with 98.4% capacitance retention after 2000 cycles; and good rate performance (211 F g ^-1 at 11 A g ^-1 ). This work provides a unique self-doped three-dimensional hierarchical porous carbon material with a favourable charge storage capacity and at the same time finds a high value-added and environment-friendly strategy for disposal and recycling of digested sludge.
Competing Interests: We declare we have no competing interests.