Tunable 2D bimetallic NiCo-MOFs with engineered crystals for high-performance supercapacitors

Abstract

Metal–organic frameworks (MOFs) are regarded as potential electrode materials for various energy conversion and storage devices. However, the low efficacy of most MOF materials impedes their use in real-time applications. Hence, we envisioned boosting the capacitive behavior of these MOF materials by doping them with metal ions and preparing bimetallic MOFs. Binder-free electrodes were fabricated by in situ growth of Ni-MOFs on nickel foam using a hydrothermal method. Further, Co metal ions were introduced to prepare a bimetallic NiCo-MOF. The bimetallic MOF exhibits exceptional capacitance, which corresponds to the synergistic effect of different metal ions. Among the synthesized MOFs, NiCo-MOF (1 : 2) shows the highest specific capacitance of 2335 F g⁻¹ and energy density of 98.3 Wh kg⁻¹ at 1 A g⁻¹ current density. The superior activity of NiCo-MOF (1 : 2) is due to its higher pore volume, which facilitates greater charge storage capacity. In addition, NiCo-MOF (1 : 2) exhibited excellent stability with 81% capacitance retention after 5000 galvanostatic charge–discharge (GCD) cycles. Thus, the performance of NiCo-MOF (1 : 2) achieved through metal ion doping and in situ growth on nickel foam opens a new avenue for the development of more competent energy conversion and storage devices.