Self‐doping porous carbon materials synthesis from bio‐wastes sodium lignosulfonate with high performance for supercapacitors

A facile method for synthesis of biomass-derived porous carbon from bio-wastes sodium lignosulfonate is proposed. Using neutral reagent KNO3 as activator and nitrogen source, the porous carbon materials with three-dimensional hierarchical porous structure interconnected oxygen, nitrogen and sulphur co-doped are prepared via simple and efficient lyophilisation and a one-step carbonization. The porous carbon carbonized at 800°C possesses high specific surface area (2400 m2 g−1) and moderate oxygen (9.15 at%), nitrogen (2.35 at%) and sulphur (0.37 at%) contents. As a result, the GSLS-800 achieves an ultrahigh specific capacitance of 389.7 F g−1 with 1 A g−1 as well as 92.3% capacitance retention with 10 000 cycles at 10 A g−1 under 3 M KOH three-electrode system. Furthermore, the solid-symmetric supercapacitor aggregated by GSLS-800 delivers a high energy density of 27.26 W h kg−1 under a power density of 487.75 W kg−1 and presents a favourable retention capacity of 89.6% at 10 A g−1 after 10 000 cycles. This work extends high value-added utilization of biomass derivatives in energy storage applications.