Journal of Electroanalytical Chemistry, Vol.566, No.2, 385-391, 2004
Surface structures at the initial stages in passive film formation on Ni(111) electrodes in acidic electrolytes
The adsorption of sulfate or OH species and subsequent Ni(OH)(2) film growth on Ni(1 1 1) single crystal electrodes has been investigated using in situ infrared reflection absorption spectroscopy (IRAs) as well as scanning tunneling microscopy (STM). In a pH 3 sulfuric acid solution, STM images show that a well-defined Ni(1 1 1) surface with a (I x 1) lattice is exposed at -300 mV, while hexagonal close-packed images with an atomic spacing of 0.32 nm are grown on this electrode at 300 mV. On the other hand, IRAs results in a sulfuric acid solution (pH 3) reveal that an absorption band at 1116 cm(-1), which can be ascribed to v(S-O) symmetric stretching of sulfate anion on Ni(1 1 1) surface, starts to appear at -400 mV and develops its intensity with an electrode potential increase, while an absorption band at 930 cm(-1) begins to develop at 0 mV on Ni(1 1 1), Ni(1 0 0) and Ni(1 1 0) electrodes, which can be assigned to an in-plane delta(Ni-OH) bending vibration in Ni(OH)(2) passive film. (C) 2003 Elsevier B.V. All rights reserved.