Nanorectangular NiFe₂O₄ Decorated with CeO₂ Nanoparticles and Modified with Phosphate Ions as an Electrocatalyst for Water Electrolysis

Efficient and clean energy technologies, such as water splitting, are essential to address environmental concerns and global energy demands. This study introduces a robust, highly stable, cost-effective electrocatalyst for water-splitting, developed through the dual-modification strategy of NiFe 2 O 4 with CeO 2 nanoparticles and phosphate (PO 4 3– ) groups. NiFe 2 O 4 was combined with the PO 4 3– group via a facile coprecipitation method at room temperature, followed by CeO 2 nanoparticles (NPs) incorporation through chemical reduction and heat treatment. The thoroughness of our research is evident in the comprehensive characterization, including X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and elemental mapping, which confirmed the electronic states and phase compositions. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) evidenced a hybrid structure of nanorectangular NiFe 2 O 4 with an average length of 560 nm and CeO 2 nanoparticles with an average diameter of 47 nm. The optimized catalyst, denoted as NiCe-2, exhibited outstanding performance in alkaline oxygen evolution reaction (OER) and Hydrogen Evolution reaction (HER), with a low overpotential of 160 and 35 mV at a current density of 10 mA cm –2, respectively. NiCe-2 also exhibited fast reaction kinetics with Tafel slopes of 33 mV dec –1 for the OER and 93 mV dec –1 for the HER, a high electrochemically active surface area (1800 cm 2 ), and long-term stability in three- and two-electrode systems with nearly 100% faradaic efficiency. In a two-electrode system for overall water splitting, it required just 1.4 V to reach 10 mA cm –2, with a maximum current density of 1000 mA cm –2 at 2.0 V. These findings highlight NiCe-2 as an exceptionally efficient and practical electrocatalyst, underscoring its significant potential for sustainable hydrogen production.