Zuliang Zhang, Huiqin Zhao, Tian Liang, Wenhao Deng, Yuanyuan Cui, Xiaojun Zeng
Transition metal selenides have emerged as potential catalysts for the oxygen evolution reaction, yet their practical implementation faces two fundamental challenges: irreversible nanoparticle aggregation under operational conditions and unfavorable adsorption energetics for critical oxygen intermediates. Herein, a strategy that integrates dual‐molten‐salt etching with hydrothermal selenization has been developed to tightly anchor FeNiSe nanoparticles onto a porous Mo‐based MXene substrate (Mo‐MXene/NiFeSe). The hierarchical porous architecture of Mo‐MXene/NiFeSe facilitates rapid mass and charge transport. The NiFeSe nanoparticles are chemically anchored within the conductive Mo‐MXene matrix via in‐situ formed Mo–O–Fe/Ni bonds, effectively preventing agglomeration during the catalytic process. Additionally, the work function gradient between Mo‐MXene and NiFeSe induces charge redistribution, creating a built‐in electric field that optimizes intermediate adsorption kinetics and enhances charge transport efficiency. Therefore, Mo‐MXene/NiFeSe achieves an ultralow overpotential of 231 mV to reach current density of 10 mA cm −2 and sustain 91% of its initial current density over 55 h in alkaline electrolyte. Density functional theory (DFT) calculations reveal that the adsorption free energy of *OOH for Mo‐MXene/NiFeSe is significantly reduced, effectively lowering the kinetic barrier of the rate‐determining step. This work provides both fundamental insights into built‐in electric field‐enhanced catalysis and a practical strategy for developing high‐performance and durable oxygen evolution reaction electrocatalysts.