Interfacial Fe-Mo electronic coupling in FeMoO₄/carbon hybrids for efficient and durable alkaline overall water...

Biomass-derived materials have emerged as sustainable and low-cost platforms for designing next-generation electrocatalysts owing to their natural abundance, tunable porosity, and carbon-rich frameworks. In this context, water splitting demands efficient electrocatalysts capable of driving both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, we develop a biomass-oriented hybrid electrocatalyst, FeMoO₄@Ds-AC, by anchoring FeMoO₄ particles with hierarchically porous activated carbon derived from date seed waste, thereby coupling catalytic activity with sustainable material design. The FeMoO₄Ds-AC catalyst improves the OER performance in an alkaline medium, achieving a low overpotential of 334 mV at 20 mA cm^-2 and a Tafel slope of 84 mV dec^-1. Subsequently, it shows an effective HER activity, with an overpotential of 75 mV at 10 mA cm^-2. The catalyst splits water with a cell voltage of 1.642 V at 10 mA cm^-2. FeMoO₄@Ds-AC has outstanding long-term durability exceeding 100 hours for both the HER and OER, with low performance degradation. The enhanced activity is attributed to the synergistic interaction between redox-active FeMoO₄ and the conductive, porous carbon matrix, which accelerates charge transfer and increases active-site accessibility. Furthermore, density functional theory (DFT) calculations are performed to gain deep insights into the interfacial coupling between FeMoO₄ and Ds-AC. The lowest interaction distance between FeMoO₄ and Ds-AC confirms the strong Fe-C and Mo-C covalent bonding and large negative binding energy (-4.61 eV), representing exothermic binding. In addition, the electronic structure analysis reveals that the strong orbital hybridization between the Mo-3d, Fe-3d and C-2p states further confirms the electronic coupling bonding between the interfacial materials. Finally, the charge density difference plots reveal that the electron density redistribution between the interfaces indicates strong Fe-C and Mo-C covalent bonding. Our DFT observations clearly demonstrate that Fe-C and Mo-C coupling enhances charge transfer and influences the OER performance. This paper describes a sustainable and effective technique for developing biomass-derived bifunctional electrocatalysts for water splitting applications.