Solid oxide cells (SOCs) are efficient energy conversion and storage devices. The development of fuel electrodes with high electrochemical activity is very important for the SOCs with high efficiency, power output and durability. In this work, the La 0.43 Ca 0.37 Ti 0.94 Ni 0.06 O 3- δ (LCTN) perovskite-type fuel electrode was successfully decorated with CeO x , FeO x , CoO x and ZnO x nanoparticles (NPs) (donated as LCTN-X, X = Ce, Fe, Co, Zn) by a simple hydrothermal method. Results show that the LCTN-X electrodes are characterized by the large in situ exsolved Ni NPs (35.3 ± 8.7 nm) and a uniform coverage of decorated metal oxide NPs with much smaller sizes: 6.8 ± 3.0 nm for LCTN-Ce, 6.6 ± 2.0 nm for LCTN-Fe, 6.9 ± 2.7 nm for LCTN-Co, and 6.7 ± 1.8 nm for LCTN-Zn after being reduced in H 2 at 800 °C for 2 h. The as-decorated LCTN-X fuel electrodes exhibit better electrochemical activities for CO 2 electrolysis and H 2 oxidation than the pristine LCTN electrode with only in situ exsolved Ni NPs. Microstructure and phase analysis reveals that the enhanced electrochemical performance is mainly due to the decorated metal oxide NPs with increased reactive sites and oxygen vacancy concentrations in the LCTN-X electrodes. The present work demonstrates that the hydrothermal-decoration strategy can be applied in the modification of perovskite-type fuel electrode surface to further enhance the SOC performance.
Development of fuel electrodes for reversible solid oxide cells (RSOCs) is important for achieving good performance and stability under both solid oxide fuel cell and electrolysis cell operation modes. In this work, CeO2-decorated La0.43Ca0.37Ti0.94Ni0.06O3−δ (denoted as LCTN-Ce) fuel electrodes were prepared via a simple hydrothermal route, where CeO2 is uniformly decorated onto the external surface of the LCTN-Ce electrode with in situ exsolved Ni nanoparticles (NPs) after reduction treatment. The decorated CeO2 content can be regulated by adjusting the hydrothermal treatment time and precursor solution concentration. As the decorated CeO2 content increases from 0.81 to 2.05%, the conductivity of the LCTN-Ce electrode decreases while the oxygen vacancy concentration increases, comprehensively affecting the cell power output and CO2 electrolysis activity. The electrolyte-supported cell assembled with LCTN-1.46Ce cell with a moderate CeO2 content of 1.46% shows an excellent reversible electrochemical performance and RSOC stability in 50% H2/50% CO2 at 750 °C. The hydrothermal decoration provides a facile way to modify perovskite oxides, and the LCTN-Ce with in situ exsolved Ni NPs and surface-decorated CeO2 is proved to be a potential RSOC fuel electrode material.
A high temperature solid oxide electrolysis cell is recognized as a promising technology for CO2 conversion (CO2-SOEC). The development of alternative cathode materials substituting conventional Ni/YSZ is a great challenge for SOECs, on which multi-step elementary reactions (e.g., adsorption of CO2, conversion of reaction intermediates, and desorption of CO) occur in succession. Herein, the Ce decorated La0.43Ca0.37Ti0.94Ni0.06O3−δ perovskite (denoted as LCTNi-Ce) is synthesized and applied as a potential cathode electrocatalyst for a CO2-SOEC. The in situ exsolution strategy and A-site deficiency enable the surface decoration of plenty of Ni nanoparticles (NPs) serving as efficient reactive sites. Furthermore, the Ce decoration leads to increased oxygen vacancy concentration, accelerated oxygen exchange rate and improved CO desorption capacity. The symmetrical half-cell measurement confirmed the boosted electrolysis performance in both CO2/CO and CO2/H2 atmospheres. DRT analysis further evidences the facilitated oxygen ion transportation and gas adsorption/dissociation upon Ce decoration. Compared to a LCTNi cell, the LCTNi-Ce cell exhibits a significantly promoted current density of −0.557 A cm−2 in 50% CO2/50% H2 at 800 °C and 1.3 V, and a reduced Rp value of 0.514 Ω cm−2 under OCV condition.
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