Preparation and electrochemical performance study of Ni Co LDH coupled materials supported on coal gasification fine ash-derived activated carbon

Coal gasification fine ash (CGFA), one of the carbon-based solid wastes generated during coal gasification) was characterized by high emissions, high carbon content, and difficult to treat, and it faced serious environmental pollution and high solid waste treatment costs. In order to promote the resourceful and high-value utilization of CGFA, CGFA-derived activated carbon/NiCo layered double hydroxide (LDH) coupling materials were prepared via low-temperature alkali fusion-KOH activation-hydrothermal synthesis in this study. By comparing the physicochemical properties and electrochemical performance of coupled materials with different Ni:Co ratios, it was evident that changes in the Ni:Co ratio had little influence on the Brunauer-Emmett-Teller specific surface area (SBET) of the samples. When the Ni:Co ratio was increased from 1:1 to 9:1, there was a gradual decrease in the relative content of surface Ni2+ and Co2+ ions in the samples. Under the condition of Ni:Co = 1:1, the sample exhibited a BET specific surface area of 758.55 m2/g, a relative content of 21.12 % for 2p3/2 Ni2+, and a relative content of 24.60 % for 2p3/2 Co2+. As the Ni:Co ratio decreased, the specific capacitance of the samples increased. When the Ni:Co ratio was 1:1, the sample exhibited a specific capacitance of 641 F/g (at 5 A/g) and a rate capability of 68.64 % (from 5 A/g to 50 A/g) in a three-electrode system. An asymmetric supercapacitor assembled with this sample achieved an energy density of 18.36 Wh/kg (corresponding power density of 5400 W/kg) and demonstrated a higher cycling stability with a retention of 83.99 % after 5000 cycles.