Hierarchical NiFeP Nanoflowers on the MXene Film as a Self-Standing Bifunctional Electrode toward Superior Overall Water Electrolysis

The exploitation of highly active, nonprecious metal bifunctional electrodes to facilitate the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for water electrolysis to produce hydrogen, but the performances are still unsatisfactory. Herein, a facile strategy was proposed to fabricate a three-dimensional (3D) bimetallic phosphide (NiFeP) nanoflower array on a self-standing assembled MXene nanosheet film (denoted as NiFeP@MXene) as a structurally integrated electrode for overall water splitting. The NiFeP@MXene film with 3D hierarchical nanoflower structures can be directly used as an electrode without traditional polymer binders, which significantly reduces the contact resistance and facilitates the electron transfer at the interface. Meanwhile, an interfacial synergistic coupling is created between the highly conductive MXene film and the bimetallic phosphides, which is favorable for the catalytic activity. Moreover, the addition of Fe improves the intrinsic activity and simultaneously facilitates the formation of 3D flower-like structures with more active sites. Thus, the self-standing NiFeP@MXene electrode demonstrates an excellent bifunctional catalytic activity in the alkaline electrolyte with small overpotentials of 240 and 122 mV to drive 10 mA cm–2 current density for the OER and HER, respectively, along with a superior overall water electrolysis performance compared to the commercial precious IrO2∥Pt/C catalyst.