Chemical and electrochemical behaviour of Ni-Ti in the cathodic conditions used in molten carbonate fuel cells

The chemical and electrochemical behaviour of nickel-titanium alloys is investigated in molten Li2CO3 + Na2CO3 at 650 degreesC under the usual MCFC cathode conditions. XPS, XRD and SIMS analyses show that Ni-Ti alloy is mostly covered by a TiO2 inner layer and by a Li2TiO3 or LixNayTiO3 outer layer. Only traces of nickel species can be detected. Ocp and conductivity measurements confirm general behaviour closer to titanium than to nickel compounds. An intercalation/deintercalation phenomenon involving the alkali titanate present at the surface of a Ni-Ti electrode was analysed by cyclic voltammetry. It can be noted that nickel compounds have a positive effect on the conductivity, but their influence on the surface characteristics of the alloy is difficult to analyse precisely. (C) 2001 Elsevier Science B.V. All rights reserved.