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 nanosheets 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 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 towards urea oxidation reaction (UOR). Moreover, the urea-assisted overall water-splitting voltage was found to be 1.5 V at the current density of 10 mA cm. 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 at 1 mA cm which was found to be 1.5 times higher than NiMn-LDH (1724.3 mC cm). 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 at a power density of 493 W kg with 77.8 percent capacity retention after a continuous run of 8000 cycles at 10 mA cm current density. Hence, the multifaceted properties of energy conversion and storage of LDH-D NiMn-MOF outline its performance in real-world applications.