A Sustainable Approach to Hydrogen Production: Sonochemical-Assisted Synthesis of CoFe 2 O 4 Nanoparticles for Use as Electrocatalysts in Water Electrolysis

The quest for sustainable hydrogen production via water electrolysis requires the development of efficient, non-precious-metal electrocatalysts. This work presents the sonochemical-assisted synthesis of cobalt ferrite (CoFe 2 O 4 ) nanoparticles as a sustainable alternative to noble metal catalysts. Nanoparticles were synthesized by varying the ultrasonic tip power (40%, 50%, and 60%) to investigate the this effect on their structural and electrochemical properties. Comprehensive characterization using X-ray diffraction, Mössbauer spectroscopy, and transmission electron microscopy confirmed the formation of phase-pure nanoscale spinel structures, with crystallite size increasing from 11.28 to 21.79 nm as the sonication power increased. Electrochemical analysis revealed that the sample synthesized at 60% power (CoFe 2 O 4 -60) exhibited the highest electrocatalytic performance among the synthesized samples for both the hydrogen and oxygen evolution reactions (HER and OER) in alkaline media. This superior performance is attributed to its largest electrochemically active surface area (ECSA = 6.95 cm 2 ) and lowest overpotentials ( η 10 = − 360 mV for HER and 410 mV for OER). Despite the larger crystallite size, high-power sonication induced higher density of surface defects and roughness, as evidenced by Mössbauer spectroscopy and electrochemical capacitance measurements. Furthermore, all samples exhibited excellent operational stability during 120 h of chronopotentiometric testing. Moreover, the efficiency of the electrolizer for water splitting was calculated to be 64.7%. These findings demonstrate that ultrasonic power tuning can influence the structural and electrochemical properties of CoFe 2 O 4 nanoparticles, contributing to improving durability and bifunctional efficient electrocatalytic activity for alkaline water electrolysis.