Surface engineered NiFe2O4/SnO2/CeO2 ternary heterojunction for dual applications in photocatalytic water treatment and supercapacitors

Abstract

Surface-engineered ternary NiFe₂O₄/SnO₂/CeO₂ (NFO/SnO₂/CeO₂) heterojunctions were synthesised through a facile hydrothermal route to deliver dual-function material for visible-light photocatalysis and electrochemical energy storage. Comprehensive structural, optical and morphological characterisation confirmed intimate interfacial coupling between the three oxides, a mesoporous architecture (72.99 m² g⁻¹) and a narrowed band gap of 1.53 eV, all of which promote efficient charge separation and extended visible-light harvesting. Under visible light irradiation, the optimised composite achieved 97.92% degradation of tetracycline within 60 min, five to nineteen-fold higher than the pristine or binary counterparts, following pseudo-first-order kinetics (k = 0.04018 min⁻¹). Reactive-species quenching identified ˙O₂⁻ and ˙OH radicals as the dominant oxidants, and the catalyst retained >85% activity after five cycles, demonstrating excellent photostability. This same material delivered a high specific capacity of 106.7 mA h g⁻¹ at 1 A g⁻¹, a coulombic efficiency of 98.7% and 74.5% capacity retention over 4000 charge–discharge cycles in 6 M KOH, outperforming the individual oxides owing to synergistic redox behaviour and rapid ion diffusion across the heterointerfaces. This work provides mechanistic insights and a scalable synthesis platform for designing next-generation multifunctional oxides integrating photocatalytic and supercapacitive functions within a single, magnetically recoverable nanocomposite for environmental and energy applications.