Enhancement of adsorption and energy storage capacity of biomass-based N-doped porous carbon via cyclic carbothermal reduction triggered by nitrogen dopants

Abstract

Alkali salt is a porogen for the synthesis of biomass based N-doped porous carbon (NPC) material. Reported results indicate that the porosity improvement of NPC material is often at the expense of its nitrogen content via alkali metal complexation and carbothermal reduction reactions, but the in-depth mechanism for the porosity improvement is still unclear which is of great importance to directionally fabricate a desired NPC material. Herein, biomass is activated by KCNO activator (a product from complexation reaction between alkali salt and N dopant) and melamine (N dopant) to further understand the production mechanism of NPC material. At 700 °C, it is observed that KCN from carbothermal reduction product of KCNO also can consume N dopant, to produce new alkali species (KCNO). Excitingly, this will support a cyclic carbothermal reduction activation of biomass, showing the surface area increase but N content decrease of NPC material. Accordingly, the porous structure is owing to the progress of cyclic carbothermal reduction reaction between KCNO and carbon matrix (KCNO + C → KCN + CO). The as-prepared material exhibits high BET surface area (3046 m2/g), or high N content (10.8%). Therefore, the prepared materials exhibited high bisphenol A adsorption capacity and electrochemical performance.