High-yield preparation of coal tar pitch based porous carbon via low melting point fire retardant carbonation strategy for supercapacitor

Currently, the preparation of porous carbon materials with low-cost, high yield and excellent capacitive performance that carbonized carbon precursors in air is suffering from strong technical bottlenecks. In this work, we reported an efficient and simple method for the preparation of high yield porous carbon by carbonizing coal tar pitch (CTP) with the assistance of fire retardants in muffle furnace in air. We investigated in detail the effect of potassium salt fire retardants with different melting points on the yield and morphology of porous carbon, and the fire retarding mechanism in air. Fire retardants could not only prevent CTP from burning completely, but also used as heteroatomic source and morphology regulator to get the heteroatom doped honeycomb structure carbon. It was found that the lower the melting point of the fire retardants, the higher the carbon yield. The yield of N and F doped porous carbon (CKKF700-3) prepared by the optimized K2CO3-KCl-KF molten salt fire retardant was 40.2 wt%, and exhibited excellent supercapacitor performance (379.8F g−1). The energy density of the symmetrical supercapacitor device composed of CKKF700-3 and K2CO3 based deep eutectic solvent electrolyte was 43.7 Wh kg−1, and it could work properly at extreme temperature from −25 to 105 °C