Transition Metal Ions Synergistic Bilayer H₂O Pillared MXene Directing In Situ Ordered Embedding Growth of Highly Efficient NiFe Alloy Catalysts

Abstract Efficient, stable, and inexpensive electrocatalysts are essential to overcome the high overpotential and slow kinetics of the oxygen evolution reaction (OER) process during water electrolysis applications. 2D transition metal carbides (MXene) show great potential in functional heterogeneous interface engineering for electrocatalytic OER. However, it is still a challenge to regulate the interlayer space and realize the heterogeneous layer‐by‐layer ordered embedding for MXene. Herein, a simple hydrothermal‐assisted strategy is proposed to prepare highly conductive Ti₃C₂T_x MXene supported by synergized Ni²⁺, Co²⁺, and Fe³⁺ with bilayer H₂O, which significantly enlarges the interlayer distances and improves the interlayer ion concentrations. Benefiting from modulated interface chemistry, embedded metal ions undergo multi‐directional in situ growth on the MXene substrate, thereby forming a stable 0D/2D@2D nano‐hybrid material (NiFe/MX‐HT). Combining density functional theory calculations with experiments demonstrates that MXene offers a framework for electron transfer, enhances the exposure of active sites, modulates the electronic structure, and greatly reduces the energy barrier of the rate‐determining step in the process of OER. Thus, NiFe/MX‐HT requires only 230 mV to achieve 10 mA cm⁻² and maintains stability even after operating at 100 mA cm⁻² for 150 h. This work offers new insights into exploring various functional MXene‐based heterogeneous materials.