Metal–Organic Framework-Derived Fe-Doped Ni3Fe/NiFe2O4 Heteronanoparticle-Decorated Carbon Nanotube Network as a Highly Efficient and Durable Bifunctional Electrocatalyst

Strategic design and fabrication of a highly efficient and cost-effective bifunctional electrocatalyst is of great significance in water electrolysis in order to produce sustainable hydrogen fuel in a large scale. However, it is still challenging to develop a stable, inexpensive, and efficient bifunctional electrocatalyst that can overcome the sluggish oxygen evolution kinetics in water electrolysis. To address the aforementioned concerns, a metal-organic framework-derived Fe-doped Ni₃Fe/NiFe₂O₄ heterostructural nanoparticle-embedded carbon nanotube (CNT) matrix (Fe(0.2)/Ni-M@C-400-2h) is synthesized via a facile hydrothermal reaction and subsequent carbonization of an earth-abundant Ni/Fe/C precursor. With a novel porous nanoarchitecture fabricated by a Ni₃Fe/NiFe₂O₄ heterostructure on a highly conductive CNT matrix, this catalyst exhibits exceptional bifunctional activity during water electrolysis over the Ni/Fe-based electrocatalysts reported recently. It delivers a low overpotential of 250 mV to achieve a current density of 10 mA/cm² with a small Tafel slope of 43.4 mV/dec for oxygen evolution reaction. It requires a low overpotential of 128 mV (η₁₀) for hydrogen evolution reaction and displays a low overpotential of 1.62 V (η₁₀) for overall water splitting. This study introduces a facile and straightforward synthesis strategy to develop transition metal-based nanoarchitectures with high performance and durability for overall water-splitting catalysis.