Fe Doped Ni₃S₂ Nanosheet Arrays for Efficient and Stable Electrocatalytic Overall Urea Splitting

In environmental and energy aspects, it is important to study electrocatalytic urea splitting. Urea electrolysis has great prospects for wastewater treatment and purification, and is an efficient way to produce hydrogen energy. In this work, we fabricated the Fe-doped Ni3S2 nanosheet arrays on nickel foam through two-step facile hydrothermal method, and discovered that Fe doped Ni3S2 with Ni/Fe = 0.25:0.75 ((Ni0.25Fe0.75)3S2/NF) presented a highly efficient performance and durability for both hydrogen evolution reaction and urea oxidation reaction (UOR). More notably, (Ni0.25Fe0.75)3S2/NF only requires a voltage of 1.49 V at 10 mA cm–2 for overall urea splitting, and has excellent electrochemical stability for more than 100 h. The remarkable electrocatalytic activity can be ascribed to the Fe doping which modifies the coordination environment of Ni and optimizes the binding strength of UOR intermediates on Ni active sites. Furthermore, density functional theory calculation manifests that Fe-doped Ni3S2 exhibits higher intrinsic activity for lower Gibbs free energy in comparison with that of pristine Ni3S2. The present results demonstrate that nickel-based materials have great potential for urea electrolysis, providing significant insights into the preparation of nonexpensive transition metal electrocatalysts.