Molten salt–assisted thermoelectric conversion of biomass for high-capacitance carbon materials

The growing global energy crisis and increasing greenhouse gas emissions necessitate the development of sustainable energy technologies. However, existing methods for synthesizing biomass-derived carbon materials suffer from limitations such as poor conductivity during low-temperature carbonization, high energy consumption during high-temperature activation, and the need for corrosive reagents, resulting in suboptimal electrochemical performance of the carbon materials. To address these challenges, this study proposes a novel composite thermoelectric dual-field electrochemical technology that converts lignin into high-capacitance carbon materials under low-temperature conditions (550 ℃). Using alkali lignin and poplar leaves as raw materials, the products obtained through pyrolysis (2 h) and electrolysis (4 h, 2.8 V) exhibited specific surface areas of 286 and 388 m 2 g − 1 , respectively. In a three-electrode system, the specific capacitance at a current density of 0.5 A g − 1 reached 230 and 177 F g − 1 ; at a current density of 0.1 A g − 1 , the specific capacitance reached 343 and 270 F g − 1 . Furthermore, the resulting materials exhibited excellent rate capability and cycling stability; after 5,000 charge-discharge cycles in a 6 M KOH aqueous solution at a current density of 5 A g − 1 , the capacitance retention rates reached 99.6% and 99.5%, respectively. This molten salt-assisted thermoelectric dual-field method provides a new approach for the low-temperature, efficient preparation of porous carbon materials for biomass-based supercapacitors. Graphical