A novel approach to preparing nano-size Co₃O₄-coated Ni powder by the Pechini method for MCFC cathodes

The dissolution of nickel oxide cathodes in the electrolyte is one of the major technical obstacles to the commercialization of molten carbonate fuel cells (MCFC). A novel alternative cathode material for MCFC was synthesized, which was made of nano-size Co₃O₄ coated on the surface of Ni powder using a polymeric precursor based on the Pechini method. X-Ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), electron microprobe analysis (EPMA), and Raman spectrometry were employed in characterization of the novel alternative cathode materials. The Co-coated Ni cathode prepared by the tape-casting technique has a lower solubility in the molten carbonate than in the NiO cathode under CO ₂ : O₂ (67 : 33) atmosphere at 650°C. The reason is that the nano-size Co₃O₄-coated Ni powder can significantly retard the dissolution of NiO in molten carbonate due to the formation of the stable LiCO_1-yNi_yO₂ phase on the surface of NiO in molten carbonate. During 300 h cell operation, the closed-circuit voltage (CCV) of unit cells using NiO and Co-coated Ni cathodes were found to be 0.80 V and 0.82 V, respectively, at a current density of 150 mA cm^-2. The results show that the Co-coated Ni cathode used as an alternative cathode could resolve the problems in scale-up of the electrode and lengthen the lifetime of MCFC.