Effect of Dy on the corrosion of NiO/Ni in molten (0.62Li,0.38K) 2CO 3

Abstract

The dissolution of NiO cathodes and the balance between the corrosion and contact ohmic resistance of current collector materials in molten carbonates are great obstacles to the commercialization of molten carbonate fuel cells (MCFC). Rare-earth element dysprosium was proposed to modify the NiO cathodes and to alloy nickel to explore its possible applications in MCFC. The measured solubility of NiO impregnated with 0.5–3 wt.% Dy in (0.62Li,0.38K) 2CO 3 at 650 °C in 60% CO 2–40% O 2 indicated that Dy addition increased noticeably the stability of NiO, while 1 wt.% Dy content produced better effectiveness. An investigation of the passive behavior of nickel and of Ni–Dy alloys containing 1–10 wt.% Dy in molten (Li,K) 2CO 3 with dynamic polarization measurements as well as X-ray diffraction and X-ray photoelectron spectroscopy indicated that the addition of Dy to nickel decreased its passive anodic current, and thus improved its corrosion resistance. The lithiation of NiO in the melt was a very significant reaction that could be promoted by the Dy additives to a certain extent, and increased the electrical conductivity of NiO.