- This work presents the design of air-stable core–shell zero-valent iron–nickel nanofilaments supported on silica and zeolite, developed to overcome the oxidation limitations of nano zero-valent iron in environmental catalysis. The nanofilaments feature ∼ 100 nm iron–nickel cores surrounded by ultrafine iron-rich threads embedded with aluminates and silicates, originating from partial support dissolution during synthesis. By varying the iron reduction time, three catalysts were prepared: one on silica reduced for 30 min, and two on zeolite reduced for 30 and 15 min. They were thoroughly characterized using nitrogen physisorption, X-ray diffraction, electron microscopy with elemental analysis, Mössbauer spectroscopy, and small-angle X-ray scattering. The zeolite-supported catalyst reduced for 15 min showed the highest activity for hexavalent chromium reduction (rate constant 8.054 min−1), attributed to a higher fraction of reactive iron–nickel phases formed under shorter reduction. ItsThis work presents the design of air-stable core–shell zero-valent iron–nickel nanofilaments supported on silica and zeolite, developed to overcome the oxidation limitations of nano zero-valent iron in environmental catalysis. The nanofilaments feature ∼ 100 nm iron–nickel cores surrounded by ultrafine iron-rich threads embedded with aluminates and silicates, originating from partial support dissolution during synthesis. By varying the iron reduction time, three catalysts were prepared: one on silica reduced for 30 min, and two on zeolite reduced for 30 and 15 min. They were thoroughly characterized using nitrogen physisorption, X-ray diffraction, electron microscopy with elemental analysis, Mössbauer spectroscopy, and small-angle X-ray scattering. The zeolite-supported catalyst reduced for 15 min showed the highest activity for hexavalent chromium reduction (rate constant 8.054 min−1), attributed to a higher fraction of reactive iron–nickel phases formed under shorter reduction. Its tailored core–shell structure improves air stability and surface reactivity, highlighting its potential as a next-generation zero-valent iron nanocatalyst for aqueous remediation…

