Heterogeneous nanocomposite of MOF-derived (NiCo)Se2 nanospheres decorated with rare earth oxide nanorods for high-performance electrochemical energy storage

In this article, MOF-derived (NiCo)Se2-x-CeO2 sphere-rod structure composite with mixed ligands (BPDC: biphenyl-4, 4′-dicarboxylic acid, PTA: terephthalic acid) is constructed via a two-step solvothermal technique. The carboxyl functional groups of BPDC act as nucleation modulation to inhibit transverse growth of MOF by enhancing steric hindrance, and two symmetric carboxyl groups and unsaturated metal nodes of adjacent layers generate the coordination, thus forming ordered nanostructures with relatively large aspect ratio. The structure produces larger pores to balance the opposite and different rate of diffusion for metal and nonmetallic ions in hydrothermal selenization. The construction of heterostructure by combining highly reactive (NiCo)Se2 with low reactive CeO2 improves diffusion kinetics. As-prepared (NiCo)Se2–3:7-CeO2 derived from MOF-3:7-CeO2 of largest aspect ratio generates large mesopore to achieve strong penetration of electrolyte ions and exhibits enhanced performance through synergistic interaction between all components on heterointerface. After testing, the (NiCo)Se2–3:7-CeO2 (PTA:BPDC = 3:7) electrode shows superior specific capacitance of 2715 F g−1 (1222 mAh g−1) at 1 A g−1. The assembled (NiCo)Se2–3:7-CeO2//AC HSC (hybrid supercapacitor) delivers energy density of 45.9 Wh kg−1 at power density of 747 W kg−1.