Electrodeposition of Epitaxial Magnetite Films and Ferrihydrite Nanoribbons on Single-crystal Gold

Magnetite (Fe₃O₄), ferrihydrite (Fe 10O14(OH)2), and iron (Fe) films were electrodeposited by cathodic deposition from an alkaline Fe(III)-triethanolamine solution. The electrodeposited phase depended on the applied potential. Magnetite films were electrodeposited from -1.01 to -1.10 V vs Ag/AgCl, whereas ferrihydrite films were deposited from -1.10 to -1.20 V vs Ag/AgCl. Iron deposition occurred at more negative potentials. The polycrystalline films were characterized using X-ray diffraction, scanning electron microscopy, and Mössbauer spectroscopy. Epitaxial magnetite films on low-index gold crystals were produced at three different potentials. X-ray diffraction analysis of the magnetite films deposited at -1.01, -1.05, and -1.10 V vs Ag/AgCl showed [111] oriented films on Au(111) and Au(001). Because of twinning of the 111 planes, the [511] orientation was present in thicker films. Magnetite grew with a [110] orientation on Au(110). At the more negative potentials of -1.10 and -1.20 V vs Ag/AgCl, ferrihydrite deposited with an (1120) orientation. © 2009 American Chemical Society.