Ifeanyichukwu Daniel Unachukwu

 

Synthesis and characterization of A-site substituted Lanthanum Nickelates as oxygen Electrodes for Solid Oxide cells

FULLPROF refined X-ray diffraction pattern of La2Ni0.8Co0.2O4+δ and the corresponding scanning electron microscope image. Copyright: Ifeanyichukwu Daniel Unachukwu FULLPROF refined X-ray diffraction pattern of La2Ni0.8Co0.2O4+δ and the corresponding scanning electron microscope image.

Lanthanide nickelates, Ln2NiO4+δ (Ln = La, Pr, Nd), has attracted much attention as oxygen electrode for Solid Oxide Cells (SOC) within the last few decades. This can be attributed to its mixed valence of the transition metal cation (Ni) as well as the presence of mobile additional oxygen atoms. Hence, they are regarded as a good Mixed Ionic and Electronic Conductors (MIEC). Furthermore, they have very good electro-catalytic activity due to their high values of oxygen diffusion coefficient (D*) and the surface exchange coefficients (K*). The measured values of these coefficients were found to be several orders of magnitude above the traditional LSM and LSCF. In addition to higher coefficients, they have very good electrical conductivity and thermal expansion property that matches those of the electrolyte materials.

A recent literature has reported enhanced electrochemical properties when Cobalt is substituted at the B-site of the Lanthanide nickelate (Ln2Ni0.8Co0.2O4+δ). Therefore, the aim of this thesis is to further improve the physico-chemical and electrochemical properties of this lanthanide nickelate through A-site substitution with bivalent alkaline earth metal (for ex. Strontium) i.e. Ln2-xSrxNi0.8Co0.2O4+δ, (x = 0.05, 0.1, 0.2, 0.4, and 0.8).