Effects of Transition Metals on the Electrical Conductivity of M‑Doped MnCo₂O₄ (M = Cu, Ni, Zn) as Contact Layer on Precoated SUS441 in Solid Oxide Cells

Spinels have been widely employed as contact layers (CLs) on metallic interconnects for solid oxide cells (SOCs) with the required electrical conductivity and Cr block ability. In this work, MnCo2O4 spinels doped with different transition metals (Cu, Ni, and Zn) were deposited on precoated SUS441 stainless steel as CLs. A positive doping effect of Cu and Ni on increasing the concentration of Mn4+/Mn3+ and Co3+/Co2+ hopping pairs was observed, whereas a negative doping effect of Zn on electrical conductivity was confirmed, which was reflected in the data of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectra (XAS). The Cu-doped Mn1Co1.7Cu0.3O4 spinel exhibited the best electrical conductivity with a low area specific resistance (ASR) value of 4.5 mΩ·cm2 at 850 °C. A relative degradation test demonstrated that Mn1Co1.7Cu0.3O4 maintained significant performance during a 200 h isothermal process. Cross-sectional observations revealed that the thickness of the Cr oxide scale formed during the degradation test was much reduced by the Mn1Co1.7Cu0.3O4 CL, which was attributed to the improved resistance to Cr oxidation. The present work shed light on the design of highly conductive CLs in SOCs

Toward High CO Selectivity and Oxidation Resistance Solid Oxide Electrolysis Cell with High-Entropy Alloy

Ni-based cermet materials still persist as pronounced challenges for electrocatalysts in solid oxide electrolysis cells (SOECs), due to their insufficient CO2 catalytic efficiency and inferior resistance to oxidation. In this paper, a (Fe,Co,Ni,Cu,Mo) quinary high-entropy alloy is explored as an alternative cathode material, offering enhanced performance in the co-electrolysis of H2O and CO2 for renewable syngas production. In comparison to traditional nickel-based cathodes, an assembled SOEC employing the as-designed quinary high-entropy alloy exhibits a remarkable increase in CO2 conversion capacity and significantly enhanced oxidation resistance. In addition, the electrolysis current density increases by 18%, and a stability test for more than 110 h reveals no degradation. Moreover, the stability can be maintained for up to 40 h even without any protective gas. Morphological and spectroscopic analyses, coupled with density functional theory (DFT) calculations, elucidate that the high-entropy effect facilitates surface electron redistribution, which in turn contributes to the measurable activity by reducing the energy barrier of CO2 activation. Notably, the superior resistance to oxidation primarily originates from the in situ-formed spinel phase under oxidation conditions. This study demonstrates the satisfying performance of high-entropy alloys as cathode materials in SOEC, validating their high application potential in this field