Prussian Blue Analogue/FeCoNi-Layered Double Hydroxide Nanorod Arrays on Nickel Foam for Urea Electrolysis

To overcome the high potential required for oxygen evolution reactions (OERs), the use of urea oxidation as an alternative to OER has attracted attention. It not only can reduce energy consumption caused by the high overpotential of OER but also simultaneously removes the urea present in polluted water, having a huge potential in industrial applications. Ni- and Fe-based transition metal hydroxides have been shown to be significantly effective in OER and urea oxidation reactions (UORs). Herein, by using FeCoNi layered double hydroxide (FeCoNi-LDH) nanorods as the precursor, we successfully develop the Prussian blue analogue (PBA)/FeCoNi-LDH nanorods grown uniformly on the surface of nickel foam (NF). The obtained electrocatalyst PBA/FeCoNi-LDH/NF nanorods as the anode could provide a current density of 100 mA cm–2 at the applied potential of 1.383 V in 1.0 M KOH solution with 0.5 M urea. The two-electrode electrolyzer (PBA/FeCoNi-LDH/NF∥Pt/C/NF) needs only 1.52 V (vs reversible hydrogen electrode, RHE) to afford the same current density. The high conductivity and 3D porous structure created by the Ni substrate can lead to superior electrocatalytic activity. Nanoarrays are constructed intimately with the base and allow the rapid escape of newly produced gas molecules, and a large number of active sites and rapid charge transfer can be induced by the introduction of sodium nitroprusside.