Mesoporous NiCo₂O₄ Micro/nanospheres with Hierarchical Structures for Supercapacitors and Methanol Electro–oxidation

Abstract

Abstract Mesoporous NiCo 2 O 4 materials with different 3D structures, including flower‐like hierarchical structures (NCO‐flower‐like HSs), nanoflake@nanoneedle‐like multiple hierarchical structures (NCO‐MHS) and urchin‐like hierarchical structures (NCO‐urchin‐like HSs), were prepared by using a facile, one‐step, NH 4 F‐induced hydrothermal method followed by thermal annealing. The physicochemical characterization of the as‐prepared materials was investigated by means of X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. The performance of the synthesized NiCo 2 O 4 material as supercapacitor electrode materials was measured and the results demonstrate that the NCO‐MHSs and NCO‐urchin‐like HSs exhibit high specific capacitance values of 640 and 655 F ⋅ g −1 at a current density of 1 A ⋅ g −1 , whereas the capacitance retention is 99.6 and 95 %, respectively, after 1000 cycles at a current density of 5 A ⋅ g −1 . The electrocatalytic performance of synthetized NiCo 2 O 4 for methanol electro‐oxidation was evaluated in 1 M KOH electrolyte. The NCO‐MHSs and NCO‐urchin‐like HSs deliver an electro‐oxidation current density of 51 and 48.5 A ⋅ g −1 , respectively, at 0.65 V with excellent stability. The results indicate that the hierarchical structure of NiCo 2 O 4 offers a promising electrode material for supercapacitors and methanol electro‐oxidation.