Synergistic 2D‐2D Interfacial Engineering Activates NiOOH as the Key Site on NiSe₂/Ni₃Se₄ Coupled with NiCoFe‐Layered Double Hydroxides Toward Urea Electrocatalysis

Catalytic urea‐assisted hydrogen production represents an awe‐inspiring breakthrough, advancing sustainable global energy security and environmental remediation. Herein, an innovative self‐supported heterostructure electrocatalyst, NiSe 2 /Ni 3 Se 4 @NiCoFe‐LDH/NF, is fabricated via a facile hydrothermal‐selenization‐electrodeposition method for bifunctional HER and UOR. The integration of 2D LDH nanosheets with 2D dual‐phased nickel selenides enhances active site density, structural lustiness and charge/mass transport, sustaining performance for over 60 h at high current density (100 mA cm −2 ) and achieving high Faradaic efficiencies of 98.90% for HER and 90.97% for UOR. The NSLDH‐0.7/NF exhibits low overpotential (potential) of 110 mV versus RHE (1.295 V versus RHE) to attain a current density of 10 mA cm −2 in alkaline media, with ultralow Tafel slope of 13.23 mV dec −1 (21.98 mV dec −1 ) in catalyzing HER (UOR), which is comparatively lower compared to the reported values in literature. The in situ Raman investigation highlights NiOOH as the stable active site responsible for catalyzing urea oxidation, effectively linking catalyst reconstruction to its electrochemical performance. This work demonstrates the practical viability of this appealing electrocatalyst in a two‐electrode urea electrocatalytic cell, while offering novel insight into the rational design of efficient electrocatalysts for simultaneous wastewater purification and sustainable hydrogen production.