Cobalt-Doped MnFeCrO4 Spinel as the Fuel Electrode for Solid Oxide Electrolysis Cells

Solid oxide electrolysis cells (SOECs) are devices thatconvertelectrical energy into chemical energy and are widely used for hydrogenproduction from steam or CO generation from CO2. Spinel-typeoxides are commonly used as a coating on metal interconnects becauseof their high electrical conductivity (& sigma;) in the air and matchingthermal expansion with that of the electrolyte. They have been usedas oxygen electrodes in solid oxide cells in recent years, but theirapplication in fuel electrodes was less studied. In this research,MnFeCr1-x Co x O4 (x = 0, 0.05, 0.2) spinel oxideswith a & sigma; around 0.1 S cm(-1) were used as thefuel electrode of an SOEC. The MnFeCr0.95Co0.05O4 (MFCC5) and MnFeCr0.8Co0.2O4 (MFCC20) with Co doping on the Cr site decomposed partiallyduring the water electrolysis, producing CoFe alloy and MnO particleson the parent spinels, forming a metal/oxide interface that furtherenhanced the electrocatalytic performance and durability of the cell.MFCC5 was able to achieve a current density of 1550 mA cm(-2) at 1.6 V and maintained a current density of about 600 mA cm(-2) after the 150 h durability test at 1.3 V at 800 & DEG;C.The Faraday efficiency was close to unity. The in situ exsolutionprocess driven by the cathodic current significantly changed the performanceof the cell, but a high performance was still maintained. In situexsolution of the metals from the reducible cations was a feasibleway of designing the spinel-type cathode for SOECs.

Automated summary

In this study, MnFeCr1-x Cox O4 spinel oxides with a conductivity of approximately 0.1 S cm(-1) were used as the fuel electrode of an SOEC. It was found that the MFCC5 and MFCC20 partially decomposed during water electrolysis, forming a metal/oxide interface that enhanced the electrocatalytic performance and durability of the cell. MFCC5 achieved a high current density of 1550 mA cm(-2) at 1.6 V and maintained a current density of about 600 mA cm(-2) after a 150-hour durability test at 1.3 V at 800 °C. This research also demonstrated the feasibility of in situ exsolution of metals from reducible cations in designing spinel-type cathodes for SOECs.