Electrochemical deposition of Ni on individual carbon microfiber from unbuffered NiCl2 solutions was studied for surface functionalization. Electrochemical and micro-structural analyses have been utilized to reveal ion concentration, applied potential and solution pH effects on the deposit nucleation and growth. Metal deposition efficiency on the carbon surface from these aqueous solutions increases significantly with Ni ion concentration. Polycrystalline Ni are normally formed but small amount of Ni(OH)(2) has been detected when the very low concentration solution is used. Ni electrodeposition on carbon microfiber surface changes from the progressive nucleation model at lower applied over-potentials to the instantaneous nucleation model at higher applied over-potentials before hydrogen evolution dominates. Compared to the conventionally used acidic Ni electrodeposition solutions, reproducible layered growth was observed within a wide range of deposition potentials due to formation of adsorbed intermediate layer. (C) 2013 Elsevier Ltd. All rights reserved.