Rational design and synthesis of Ni_xCo_3−xO₄ nanoparticles derived from multivariate MOF-74 for supercapacitors

Abstract

5Mixed transition metal oxides have attracted much attention recently due to their potential application in the energy and environmental sciences. The emergency of multivariate MOFs recently attracts great research attention and provides an opportunity for multivariate mixed-metal oxides. In this work, five isostructural, single-phase MOF-74 structures with different divalent metals (MOF-74-Co, MOF-74-Ni, MOF-74-NiCo1, MOF-74-NiCo2 and MOF-74-NiCo4) were synthesised by varying the mole ratios of 10 Ni/Co mixed-metal ions. After annealing at the proper temperature, Co 3 O 4 , NiO and three kinds of Ni x Co 3-x O 4 mixed-metal oxide nanoparticles with the high surface area were easily obtained and the metal ratio was readily controlled, enabling us to systematically investigate the effect of different metal species amounts on the electrochemical properties of the mixed-metal oxide materials. When these metal oxides were used as electrode materials for supercapacitors, we found that the mixed-metal oxides Ni x Co 3-x O 4 15 obtained from bimetallic MOF-74-NiCo structures had obvious advantages compared with the monometallic oxides of MOF-74-Ni and MOF-74-Co. Especially, the NixCo 3-x O 4 -1 with the Ni/Co metal ratio 1:1 exhibited the highest capacitance of 797 F g -1 and excellent cycling stability.

Rational Microstructure Design on Metal–Organic Framework Composites for Better Electrochemical Performances: Design Principle, Synthetic Strategy, and Promotion Mechanism

“…Owing to the homogenous dispersion of two metal ions inside the MOFs, the obtained bimetal oxides also exhibit a homogenous dispersion of two different metal ions inside the whole metal oxides, thus leading to a synergistic effect between different metal components at atomic level. For instance, Qiu and co‐workers reported the fabrication of Ni x Co 3− x O 4 by using bimetal MOF Ni‐Co‐MOF‐74 as precursor, which was employed as electrode materials for supercapacitors . By adjusting the molar ratio of Ni and Co, the authors found that Ni/Co with a molar ratio of 1:1 exhibited the highest specific capacitance (797 F g −1 at current density of 1 A g −1 ), much better than the metal oxides with only one kind of metal (119 F g −1 for NiO and 115 F g −1 for Co 3 O 4 ).…”

A review of performance optimization of MOF-derived metal oxide as electrode materials for supercapacitors

“…Subsequently, Chen group also synthesized a series of Ni x Co 3‐x O 4 , which were isomorphic to the Co 3 O 4 crystal structure derived from MOF‐74 topology phases (MOF‐74‐Co, MOF‐74‐Ni, MOF‐74‐NiCo1, MOF‐74‐NiCo2, and MOF‐74‐NiCo4, denoted Co: Ni = 1:0, 0:1, 1:1, 2:1, and 4:1) (Figure ). The relationship between metal ratios in the Ni x Co 3‐x O 4 and the electrochemical performance were explored.…”

“…Schematic diagram of various metal oxide materials derived from multivariate MOF‐74 crystals. Ni, cyan; Co, pink; C, gray; and O, red; the H atoms are omitted for clarity [Colour figure can be viewed at wileyonlinelibrary.com]…”

Recent advancements in metal organic framework based electrodes for supercapacitors

“…Chen et al [79] synthesized NiCo oxides by the annealing method, in the process of which Co and Ni act as the central metal ions (Fig. 16a).…”