Vanadium metal-organic framework derived oxygen vacancy-rich NiV-layered double hydroxide nanosheets for high-performance supercapacitors

Abstract

Layered double hydroxides (LDHs) are promising electrode materials for supercapacitors due to their favorable faradaic pseudocapacitance, abundant slabs, high flexibility to ion exchange and tunable chemical composition. However, these materials' slow charge transfer rate, small specific surface area, and restricted availability of exposed electroactive sites hinder their electrochemical capabilities. Metal-organic frameworks (MOFs) are frequently employed as a template for the synthesis of LDHs with tailored morphology, hence enhancing the functional properties of these materials. This study successfully created two-dimensional (2D) ultra-thin NiV-LDH nanosheets with specific oxygen vacancies (Vo) by carefully choosing a template and intentionally introducing Vo. After undergoing optimal etching operations, the surface electronic environment of V was changed, and a certain concentration of Vo was produced. As a result, the Ni-based NiV-LDH electrodes, with their electroactive metal components (Ni and V) and their synergistic interactions, demonstrated increased specific capacity. This increase was additionally supported by enhanced charge and ion transfer, improved conductivity, and greater availability of exposed electroactive sites. Among all, the NiV-LDH-60 ℃ sample showed a substantial increase in specific surface area and achieved a peak specific capacitance of 2133 F g-1 when assessed at a current density of 1 A g-1. Furthermore, the material exhibited an impressive cycling stability of 82.8% after undergoing 2000 cycles at a significant current density of 10 A g-1. The energy density of the asymmetric supercapacitor (ASC), employing NiV-LDH-60 ℃ as the cathode and activated carbon (AC) as the anode, was 24.3 Wh kg-1 while operating at a power output of 750 W kg-1. Overall, these findings contribute to a novel perspective on the synthesis of LDHs for supercapacitors, offering insights into how the morphology and electronic properties of these materials can be tailored to enhance their performance in energy storage applications.