Hydrated-Metal-Halide-Based Deep-Eutectic-Solvent-Mediated NiFe Layered Double Hydroxide: An Excellent Electrocatalyst for Urea Electrolysis and Water Splitting.

Abstract

The liquid structures of deep eutectic solvents (DESs) based on hydrated metal halides and their application as electrolytes have been widely studied. However, little attention has been paid to the direct use of this type of DES in the preparation of micro-/nanomaterials. Herein, an FeCl3 ⋅6 H2 O/urea DES was used in the one-step synthesis of NiFe-LDH_D with a nanoflower morphology. In alkaline media, this catalyst promoted excellent electrocatalytic activity for the oxidation of urea at potential of 1.32 V (vs. RHE) and for the oxygen-evolution reaction at a potential of 1.39 V to achieve a current density of 10 mA cm-2 . These results were superior to the results with NiFe-LDH/NF that was obtained from an aqueous solution of FeCl3 , as well as most of the previously reported transition-metal catalysts. Furthermore, NiFe-LDH_D/NF could be readily implemented as both a cathode and an anode for the electrolysis of urea and water splitting. The use of hydrated-metal-halide-based DESs for the preparation of LDH catalysts through a dipping-redox strategy should both enrich the research of DESs and offer guidance for the rational surface engineering of catalysts for the electrolysis of urea and overall water splitting with high performance.