NiFe phosphides coupled on Ti₃C₂T_x MXene nanosheets for high-efficiency oxygen evolution reaction in alkaline medium

The development of stable, efficient and cost-effective electrocatalysts is crucial for overcoming the sluggish kinetics of the oxygen evolution reaction (OER) in electrochemical splitting water. Ni-Fe layered bimetallic phosphides (NiFe-P) exhibit considerable promise as electrocatalysts for OER. However, their limited conductivity and low inherent activity present significant challenges. Herein, we design a novel NiFe-P/Ti₃C₂T_x composite, synthesized by hydrothermally coupling NiFe-LDH nanosheets with few-layer Ti₃C₂T_x MXene, followed by high-temperature phosphating. By optimizing the Ni/Fe ratio and controlling the phosphidation process, the Ni_2.5Fe_2.5-P/Ti₃C₂T_x catalyst demonstrates enhanced activity and stability for OER in alkaline media, achieving a low overpotential of 290 mV and a Tafel slope of 72.3 mV/dec at a current density of 10 mA cm^-2. Theoretical calculations reveal that synergistic effect of the Ni-Fe bimetallic system optimizes the local electronic environment of the phosphides, while defect sites provide additional active centers, boosting intrinsic activity. Furthermore, the high conductivity of Ti₃C₂T_x and the three-dimensional interconnected porous network accelerate charge transfer kinetics. This work underscores the substantial development potential of MXene-based electrocatalysts in advancing novel and efficient materials for OER.