Exploring Ni(Mn1/3Cr2/3)2O4 Spinel-Based Electrode for Solid Oxide Cell
The alkaline earth elements- and cobalt-free Ni(Mn1/3Cr2/3)2O4 (NMC) spinel is adopted to form composite electrodes with oxygen ionic conductive phase for symmetrical solid oxide cells, and successfully demonstrates its applicability in both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes. In H2 or CO-CO2 atmosphere, NMC decomposes to Ni and spinel, but would quickly recover to NMC in the air or pure CO2. Both NMC and NMC-Gd0.1Ce0.9O2-δ (NMC-GDC) composite electrodes reveal a high redox resistance and fast recovery, which are originated from the significant difference in Gibbs free energy when NMC is subjected to reducing and oxidizing atmospheres. Under SOFC mode and 800 °C, the anode supported and symmetrical cells with NMC-GDC electrode achieve a peak power density of 1293 and 416 mW cm-2, respectively. With an applied current density of 400 mA cm-2 at 750 °C under SOFC mode, the working voltage of the symmetrical cell with NMC-GDC electrode showed no evident decline over 96 h. Under SOFC mode and pure CO2 in cathode, the symmetrical cell works at SOEC mode showed a faradaic efficiency of over 96% at 700-850 °C and an electrolysis current density of 2320 mA cm-2 at 850 °C with an applied voltage of 2 V. Furthermore, the applied voltage decreased from 1.507 V to 1.407 V over a 72 h’s running under a static current density of 800 mA cm-2 at 800 °C. The nickel exsolution at reduction atmosphere and the abundant transition metal elements centered octahedrons admit the multi-functionality of NMC. The NMC spinel-based electrode demonstrates an extraordinary redox resistance and running stability, and it is anticipated to play a pivotal role in the future exploration of novel and stable electrode for solid oxide cells.