Facile synthesis of MOF-derived Co₉S₈/Ni₃S₂/N-doped carbon composites for supercapacitors

Transition metal sulphides derived from metal–organic frameworks (MOFs) have gained increasing attention as promising electrode materials for energy storage, owing to their elevated theoretical capacitance and exceptional electrochemical features. Herein, a simple dual organic ligand strategy and controllable pyrolysis treatment were used to prepare porous micro-rods Co₉S₈/Ni₃S₂/NC-T (T denotes for temperature) composite materials. Their structure and composition can be precisely controlled by adjusting the pyrolysis temperature. Co₉S₈/Ni₃S₂/NC-T composite materials possess rich pore structures, unique three-dimensional carbon conductive networks and synergistic effects of Co₉S₈ and Ni₃S₂. Experimental results of cyclic voltammetry revealed that the bimetal sulphides in Co₉S₈/Ni₃S₂/NC-T can provide substantial redox pseudocapacitance for electrochemical reactions. Electrochemical tests indicated that the optimal carbonization temperature was 700°C, and the Co₉S₈/Ni₃S₂/NC-700 electrode material has the highest specific capacity of 2288 F g⁻¹ at a current density of 1 A g⁻¹ and an excellent rate capability with retention of about 61.2% at a current density of 10 A g⁻¹. This study provides methodological guidance for the rational composition control and unique structure of MOF-derived materials for supercapacitors.