An investigation on room temperature synthesis of vertically oriented arrays of iron oxide nanotubes by anodization of iron

• Published in: Electrochimica acta Vol. 55; no. 3; pp. 785 - 793
• Main Authors: Rangaraju, Raghu R., Raja, K.S., Panday, A., Misra, M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2010; Elsevier
• Subjects: Anodic oxide film; Chemistry; Electrochemistry; Exact sciences and technology; General and physical chemistry; Hematite; Iron oxide nanotubes; Passive film; Hematite; Anodic oxide film; Iron oxide nanotubes; Passive film; Phosphates; Ethylene glycol; Electrolyte solution; Oxide layer; Surface layer; Nanotube; Iron; Fluorides; Array; Iron Oxides; Magnetic particles; Corrosion; Anodizing; Preparation; Anodic oxide; Glycol; Room temperature; Borates; Passivation
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2009.07.012

Formation of iron oxide nanotubes on to pure iron substrate by an electrochemical anodization method was investigated in fluoride containing electrolytes. Anodization of iron foil in fluoride containing borate solution resulted in stacked nano-ring type oxide morphology. Nanoporous oxide layer was observed at low pH and a granular oxide layer was formed at higher pH of phosphate + fluoride solutions. Formation of either nanoporous or nanotubular oxide layer was observed in ethylene glycol (EG) solution containing 0.05–0.1 M fluoride + 1.5–3.0 vol.% water. Transition from nanoporous structure to nanotubular structure was critically controlled by anodization potential, water addition and fluoride concentration of the EG solution. The potential required for this transition decreased with increase in the water content up to 7 vol.% beyond which enhanced dissolution occurred. Annealing of the nanotubes at 500 °C resulted in predominantly α-Fe 2O 3 crystal structure. The annealed Fe 2O 3 samples consisting of a single layer of nanotubular structure showed a photo current density of 0.4 mA/cm 2 at 0.5 V Ag/AgCl in 1 M KOH solution under simulated solar light illumination.