| dc.description.abstract | Layered Ruddlesden-Popper (RP) structure such as La2NiO4 has superior electrochemical activity than other cathode material for Solid Oxide Fuel Cell (SOFC). The primary purpose of this work is to explore new cathode material with higher-order Ruddlesden-Popper (RP) structure Mg-doped La2NiO4 material, which produces via Glycine-Nitrate Process (GNP). The general chemistry formula is 〖La〗_(n+1) 〖Ni〗_(n(1-x)) 〖Mg〗_nx O_((3n+1)-δ) with x is doping concentration and n as the number of RP structure layers. Three phases were taken to achieve the purpose of this work. The first phase is to explore the appropriate concentration of Mg-doped in La2NiO4. Four samples with magnesium contents varying in x= 0,0.02,0.03, and 0.04, abbreviated as LNO, LN1M2, LN1M3, and LN1M4, respectively, were investigated. Among the specimens, LN1M3 (i.e., 3% Mg-doped La2NiO4) was found the best cathode material used in SOFC, due to high nonstoichiometric oxygen-vacancy (δ), high electrical conductivity (~200 S/cm) and excellent electrochemical reactivity. In the second phase, higher-order (n=2 &3) RP structure such as LN3M3 based on LN1M3 was formed to indicate a frame of rod-like particles to reveal good electrical conductivity (i.e., σ ~ 800 S/cm) and low polarization resistance (Rp at 1.41 Ωcm2). In the final phase, specimen LN3M3 was screen-printed on different SOFC button cells to study their cathodic performance. These button cells were different in configuration (one supported by electrolyte and another supported by anode) and distinct in electrolytes (one is BaCe0.6Zr0.2Y0.2O3, BCZY, and the other is (ZrO2)0.92(Y2O3)0.08, YSZ). The results of I-V testing demonstrate different maximum power density. LN3M3 in YSZ anode-supported cell achieved the best power density Pmax 205 mW/cm2 and polarization resistance Rp 0.12 Ωcm2. The simulation of equivalent circuits of the electrochemical impedance spectroscopy (EIS) is useful to understand the difference in power density. | en_US |