Redox and Electrocatalytic Activity of Ni Ion-Implanted Ti
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Ni−Ti surface alloy was prepared by ion-implanting Ni into Ti. The surface film was amorphous having a Ni surface content of 10–40 at.%. The material was compared with a Ni−Ti bulk alloy (44.08:55.9) regarding their redox and electrocatalytic behavior in NaOH by cyclic voltammetry. The surface was characterized by x-ray photoelectron spectroscopy, x-ray and electron diffraction, transmission electron microscopy, and atomic force microscopy. The ion-implanted material revealed an enhanced activity toward the redox conversion of Ni(OH)2 ↔ NiOOH and the anodic oxidation of glucose. The effect is discussed considering the enhanced generation of active Ni surface sites from amorphous Ni and the stabilization of higher valence Ni by Ti. I. INTRODUCTION 1,2
The electrochemistry of Ni from Ni-based alloys has extensively been studied on account of its importance in many industrial applications.1–12 The electro-oxidation of many small organic molecules in alkaline media9–13 is known to be catalyzed by the surface-bound redox couple Ni2+/Ni3+. Ni−Ti alloys studied so far1,2 are bulk alloys, although the electrochemistry of solid electrodes is predominantly a surface phenomenon. Amorphous alloys are more electrocatalytically active than their crystalline counterparts.14–20 The electroactivity is closely related to the material dispersity.2,21,22 There is a great interest in optimizing the material surface regarding its redox and catalytic activity. Many surface characteristics can be modified in a defined way using ion implantation.23,24 A previous study observed an enhanced electrocatalytic activity of amorphous Ni−Ti thin film compositions (surface Ni content
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