In-situ exsolution of cobalt nanoparticles from La0.5Sr0.5Fe0.8Co0.2O3-δ cathode for enhanced CO2 electrolysis performance
image: Solid oxide electrolysis cell (SOEC) is a promising technology for CO2 conversion and renewable energy storage with unrivaled high efficiency. The CO2 electro-reduction reaction on the cathode greatly affects the SOEC performance due to the inherent high stability of CO2 molecules, while the state-of-the-art nickel-yttria stabilized zirconia metal-ceramic cathode suffers from severe carbon deposition, redox instability and Ni oxidation, arising the significance to develop alternative catalytically active SOEC cathodes for CO2 electrolysis. Herein, perovskite cathode materials with different structural stabilities are designed by Nb substitution on the Fe-site and Co-site of La0.5Sr0.5Fe0.8Co0.2O3-δ (LSFC82), respectively, to obtain La0.5Sr0.5Fe0.7Co0.2Nb0.1O3-δ (LSFCN721) and La0.5Sr0.5Fe0.8Co0.1Nb0.1O3-δ (LSFCN811). Our study demonstrates that Nb incorporation enhances structural stability and leads to a decrease in oxygen vacancy concentration and CO2 adsorption ability. LSFC82-Sm0.2Ce0.8O2-δ (SDC) cathode with inferior structural stability shows the optimal CO2 electrolysis performance with the generated current density reaching 1.80 A cm-2 at 1.6 V and 800 °C, superior to the SOECs with LSFCN721-SDC and LSFCN811-SDC cathodes, as well as most SOECs reported in other literatures. Furthermore, the SOEC with LSFC82-SDC shows exceptional operational stability during the continuous CO2 electrolysis at 1.2 V for 100 h with the Faradaic efficiency maintained at around 100%. However, LSFC82 particles are collapsed into pieces after stability test with the generation of catalytically active Co nanoparticles simultaneously. Although LSFCN721-SDC and LSFCN811-SDC cathodes possess enhanced structural stability, they exhibit a higher degradation rate compared to LSFC82-SDC, which is related to their insufficient CO2 adsorption capability. The frameworks of LSFCN721 and LSFCN811 particles maintain well because of the introduced high-valent niobium, but Co exsolution, oxygen vacancy content and the corresponding CO2 electrolysis performance are restricted. This work confirms that Co nanoparticles can be exsolved from LSFC82-SDC cathode during CO2 electrolysis and LSFC82 perovskite cathode exhibits high activity and stable CO2 electrolysis performance, providing references for constructing metallic nanoparticles decorated-perovskite cathodes for SOECs.
Credit: Jingwei LI, Dalian Institute of Chemical Physics, Chinese Academy of Sciences
Solid oxide electrolysis cell (SOEC) is a promising technology for CO2 conversion and renewable energy storage with unrivaled high efficiency. The CO2 electro-reduction reaction on the cathode greatly affects the SOEC performance due to the inherent high stability of CO2 molecules, while the state-of-the-art nickel-yttria stabilized zirconia metal-ceramic cathode suffers from severe carbon deposition, redox instability and Ni oxidation, arising the significance to develop alternative catalytically active SOEC cathodes for CO2 electrolysis. Herein, perovskite cathode materials with different structural stabilities are designed by Nb substitution on the Fe-site and Co-site of La0.5Sr0.5Fe0.8Co0.2O3-δ (LSFC82), respectively, to obtain La0.5Sr0.5Fe0.7Co0.2Nb0.1O3-δ (LSFCN721) and La0.5Sr0.5Fe0.8Co0.1Nb0.1O3-δ (LSFCN811). Our study demonstrates that Nb incorporation enhances structural stability and leads to a decrease in oxygen vacancy concentration and CO2 adsorption ability. LSFC82-Sm0.2Ce0.8O2-δ (SDC) cathode with inferior structural stability shows the optimal CO2 electrolysis performance with the generated current density reaching 1.80 A cm-2 at 1.6 V and 800 °C, superior to the SOECs with LSFCN721-SDC and LSFCN811-SDC cathodes, as well as most SOECs reported in other literatures. Furthermore, the SOEC with LSFC82-SDC shows exceptional operational stability during the continuous CO2 electrolysis at 1.2 V for 100 h with the Faradaic efficiency maintained at around 100%. However, LSFC82 particles are collapsed into pieces after stability test with the generation of catalytically active Co nanoparticles simultaneously. Although LSFCN721-SDC and LSFCN811-SDC cathodes possess enhanced structural stability, they exhibit a higher degradation rate compared to LSFC82-SDC, which is related to their insufficient CO2 adsorption capability. The frameworks of LSFCN721 and LSFCN811 particles maintain well because of the introduced high-valent niobium, but Co exsolution, oxygen vacancy content and the corresponding CO2 electrolysis performance are restricted. This work confirms that Co nanoparticles can be exsolved from LSFC82-SDC cathode during CO2 electrolysis and LSFC82 perovskite cathode exhibits high activity and stable CO2 electrolysis performance, providing references for constructing metallic nanoparticles decorated-perovskite cathodes for SOECs.