Black Liquor and Wood Char-Derived Nitrogen-Doped Carbon Materials for Supercapacitors

Herein, we present a synthesis route for high-efficiency nitrogen-doped carbon materials using kraft pulping residue, black liquor, and wood charcoal as carbon sources. The synthesized nitrogen-doped carbon materials, based on black liquor and its mixture with wood charcoal, exhibited high specific surface areas (SSAs) of 2481 and 2690 m² g^-1, respectively, as well as a high volume of mesopores with an average size of 2.9-4.6 nm. The nitrogen content was approximately 3-4 at% in the synthesized nitrogen-doped carbon materials. A specific capacitance of approximately 81-142 F g^-1 was achieved in a 1 M Na₂SO₄ aqueous solution at a current density of 0.2 A g^-1. In addition, the specific capacitance retention was 99% after 1000 cycles, indicating good electrochemical stability.