Post-treatment of ZIF-67/Ni₃S₄ Nanoparticle Composites by Metal Ions and Solvent-Assisted Etching as Advanced Electrodes for Supercapacitors

Incorporating metal compound nanoparticles into zeolitic imidazolate frameworks (ZIFs) has emerged as an effective way to solve the low conductivity issue of ZIFs, helping to boost their electrochemical performance. However, the resultant ZIFs/metal compound composites usually lack hierarchical pores, which causes the electrochemical performance to be far below expectations. Here, two rational post-treating strategies, namely, Ni 2+ /H 2 O etching and solvent-assisted etching, have been proposed to tailor the structure and composition of ZIF-67/Ni 3 S 4 composite. Especially, Ni 2+ /H 2 O etching enables the self-transformation of ZIF-67 to CoNi layered double hydroxide (LDH), while solvent-assisted etching creates hierarchical pores in ZIF-67. After post-treatments, both resultant samples display significant improvements in energy storage capability and cycling lifespan as compared to untreated ZIF-67/Ni 3 S 4 owing to their superior features including the hierarchical pore structure, enhanced pseudocapacitance property, and less internal and charge transfer resistance. The tailoring strategies together with mechanism studied here can provide perspectives and constructive designing knowledge to promote the widespread use of ZIFs or Ni 3 S 4 based advanced electrodes toward high-performance supercapacitors.