Fe-driven surface reconstruction of self-supported Ni3S2 nanosheet electrodes enables energy-efficient urea-assisted water electrolysis

Urea-assisted water electrolysis offers a promising strategy for energy-saving hydrogen production with simultaneous wastewater valorization. Herein, a self-supported Fe-decorated Ni 3 S 2 nanosheet electrode on nickel foam (Fe–Ni 3 S 2 /NF) was prepared by hydrothermal growth followed by Fe electrodeposition. Structural characterization confirmed Fe introduction preserved the Ni 3 S 2 phase while inducing surface/electronic modulation. Electrochemically, Fe–Ni 3 S 2 /NF exhibited enhanced hydrogen evolution activity with overpotentials of 160, 222, and 259 mV at 10, 50, and 100 mA cm −2 , respectively (Tafel slope: 79 mV·dec −1 ). For urea oxidation, it delivered 10, 50, and 100 mA cm −2 at 0.97, 0.99, and 1.01 V, reducing the anodic potential by ∼0.62 V vs. OER at 100 mA cm −2 . A symmetric Fe–Ni 3 S 2 /NF || Fe–Ni 3 S 2 /NF electrolyzer required only 1.58–1.86 V for 10–100 mA cm −2 and operated stably for 50 h at 50 mA cm −2 , demonstrating a scalable noble-metal-free electrode for energy-efficient hydrogen production coupled with urea oxidation.