Preparation of coal gasification fine slag-based supercapacitive carbon using hydrothermal deashing and alkali activation

The coal gasification is the key process of clean usage of coal resource, which inevitably produces a large amount of coal gasification slag (CGS), and causes serious environmental pollution and ecological damage. The high ash content of coal gasification fine slag (CGFS) prevents the efficient utilization of residual carbon in CGFS. In this work, carbon-rich component was obtained by acid leaching under hydrothermal condition and alkali washing. The eluent is rich in Al and Si elements, which can be used to prepare polyaluminum chloride and porous ceramics. The residual inorganic component after the treatment of acid and alkali is electrochemical inertness, which has not adverse effect in the capacitive performance of electrode materials. Then, the activated carbon (AC) electrode materials were prepared successfully by different activation conditions, using carbon-rich component. The results show that the AC-800-60 has the biggest specific surface area of 1267.81 m²/g and a total pore volume of 0.63 cm³/g, which are beneficial for energy storage and ion transport efficiency of electrode materials AC-800-60 also shows the high-specific capacitance of 226.24 F/g at current density of 1 A/g, which is obviously higher than the commercial Yp-50 AC. After 10,000 cycles of charge–discharge process, the specific capacitance has 101.7% capacitance retention, indicating its high stability.