In-situ formation of SrCO3 microcrystals-decorated Fe3O4 nanosheets as an efficient and long-lasting catalyst for overall water splitting
Amina Lahrichi, Youness El Issmaeli, Bruno G. Pollet
Abstract
• Hydrothermal synthesis enabled in-situ Fe 3 O 4 @SrCO 3 /NF formation with enhanced surface roughness and stability. • Catalytic performance surpassed commercial IrO 2 /NF with 243 mV OER overpotential and a low Tafel slope of 38 mV dec −1 . • DFT calculations revealed in-situ formed SrCO 3 lowers the OER energy barrier to 0.73 eV, optimizing charge redistribution. • Fe 3 O 4 @SrCO 3 /NF demonstrated outstanding stability, maintaining OER for 300 h and OWS for 125 h at 10 mA cm −2 . A novel Fe 3 O 4 @SrCO 3 /NF electrocatalyst material was developed via hydrothermal synthesis, creating a composite structure with Fe 3 O 4 nanosheets and SrCO 3 crystals on nickel (Ni) foam (NF) that enhances surface roughness and stability, in turns optimizing catalytic performance in water-splitting applications. In 1.0 M KOH, the as -prepared Fe 3 O 4 @SrCO 3 /NF achieved a low OER overpotential of 243 mV at 10 mA cm −2 , surpassing commercial IrO 2 /NF, with a Tafel slope of 38 mV dec −1 indicating rapid reaction kinetics. Electrochemical Impedance Spectroscopy (EIS) confirmed a low charge transfer resistance ( R ct ) of 1.49 Ω, indicating efficient electron mobility. For HER, Fe 3 O 4 @SrCO 3 /NF displayed a moderate overpotential of 172 mV at − 10 mA cm −2 . In a two-electrode setup with Pt/C (cathode), Fe 3 O 4 @SrCO 3 /NF (anode) demonstrated efficient overall water splitting, requiring only 1.55 V at 10 mA cm −2 , underscoring its viability for sustainable energy applications. Density Functional Theory (DFT) calculations revealed that SrCO 3 in-situ formation not only shifted the OER rate-determining step, lowering the energy barrier to 0.73 eV, but also optimized the d -band center and facilitated interfacial charge redistribution, enhancing intermediate adsorption and catalytic activity. Notably, Fe 3 O 4 @SrCO 3 /NF demonstrated exceptional stability, sustaining OER activity for over 300 h and delivering stable overall water-splitting performance for 125 h, significantly outperforming many state-of-the-art OER catalysts. This durability, combined with high catalytic efficiency, establishes Fe 3 O 4 @SrCO 3 /NF as a promising candidate in non-precious metal electrocatalysts for water-splitting technologies.