Layered double hydroxide-derived bimetallic-MOF as a promising platform: Urea-coupled water oxidation and supercapattery-driven water electrolyzer

Developing a two-dimensional (2D) ultrathin metal-organic framework plays a significant role in energy conversion and storage systems. This work introduced a facile strategy for engineering ultrathin NiMn-MOF nano- sheets on Ni foam (NF) via in situ conversion from NiMn-layered double hydroxide (LDH). The as-synthesized LDH-derived NiMn-MOF (LDH-D NiMn-MOF) nanosheet exhibited an overpotential of 350 mV to drive a current density of 100 mA cm- 2 during oxygen evolution reaction (OER) owing to its better redox activity, hierarchical architecture, and intercalating ability. The similar effective catalytic trend was noticed during the urea-assisted water oxidation process. The developed catalyst required only a potential of 1.39 V vs. RHE at 100 mA cm- 2 towards urea oxidation reaction (UOR). Moreover, the urea-assisted overall water-splitting voltage was found to be 1.5 Vat the current density of 10 mA cm- 2. Furthermore, the same catalyst was explored as an energy-storage material for supercapattery application with an aerial specific capacity value of 2613.9 mC cm- 2 at 1 mA cm- 2 which was found to be 1.5 times higher than NiMn-LDH (1724.3 mC cm- 2). Additionally, an aqueous asymmetric supercapattery device was fabricated which demonstrated the best electrochemical performance and provided a maximum energy density of 64.1 Wh kg- 1 at a power density of 493 W kg- 1 with 77.8 percent capacity retention after a continuous run of 8000 cycles at 10 mA cm- 2 current density. Hence, the multifaceted properties of energy conversion and storage of LDH-D NiMn-MOF outline its performance in real-world applications.