Facile Synthesis of Ca-Doped LaCoO₃Perovskite via Chemically Assisted Electrodeposition as a Protective Film on Solid Oxide Fuel Cell Interconnects

Abstract

Interconnects in solid oxide fuel cells (SOFCs) serve two essential roles, namely, cell-to-cell electrical connection and the separation of fuel and oxidant gases. It is of practical significance to develop a protective coating that is capable of improving the surface stability of metallic interconnects while maintaining their electrical properties. Perovskite-type oxides are recognized as promising materials for protective coatings; however, it is difficult to fabricate high-density films by conventional powder-sintering processes. In this paper, we report a facile electrodeposition-based approach to preparing perovskite oxide films on SOFC interconnects. A high density, adhesive Ca-doped LaCoO3 perovskite film of ∼1.3 μm thickness is directly formed on an SOFC interconnect through the “chemically assisted electrodeposition” of hydroxide combined with the thermal conversion of hydroxide to oxide. In the proposed synthesis method, the electrodeposition parameters, such as solution composition and deposition time, have a strong influence on the composition, microstructure, and adhesion of the perovskite oxide film. The fabricated film exhibits outstanding performance as a protective coating for SOFC interconnects, as evidenced by a low area-specific resistance of 14.4 mΩ cm2 at 800°C and high stability during both continuous operation and repeated thermal cycling.

High‐Performance Solid Oxide Fuel Cell with an Electrochemically Surface‐Tailored Oxygen Electrode

“…In the CAED step, LaCo(OH) x is conformally formedo nt he carbon-coated LSM-YSZ electrode as follows.U pon cathodic polarization,t he pH near the LSM-YSZ electrode is drastically elevated owing to the electrochemical reduction of nitratespecies (NO 3 À ), which allows spontaneous chemical precipitation of LaCo(OH) x on the electrode (Figure 1b). [30][31][32] Figure 1b shows ap otentialv ersus time profile during aC AED process performed by using ac athodic current density of 1mAcm À2 for 6min. In the previous studies, we found that ah igherc urrent density (overpotential)c auses the formationo fl arge-scale agglomerates owing to severe hydrogen evolution, whereas a lower current density (overpotential) leads to uniform deposition at as lower rate.…”

“…In the previous studies, we found that ah igherc urrent density (overpotential)c auses the formationo fl arge-scale agglomerates owing to severe hydrogen evolution, whereas a lower current density (overpotential) leads to uniform deposition at as lower rate. [30][31][32] Based on the preliminaryo ptimization study,inthis work, acathodic current density was selected in such aw ay that LaCo(OH) x could be conformally formedo n the carbon-coated LSM-YSZ electrode. The measured potentials ranged between À0.80 and À0.84 Vv ersus Ag/AgCl, which are much lower than the reduction potential of NO 3 À (À0.19 Vv s. Ag/AgCl).…”

“…Given the reductionp otentialo fC o 2 + (À0.48 Vv s. Ag/AgCl), there is the possibilityo ft he electrodepositiono fm etallicC o; however,t he NO 3 À reduction reaction with highero verpotentials would be dominant during CAED. [29][30][31] The possibility of Co electrodeposition will be further discussed during the following structurala nalysis of the LSM-YSZ cathodes. After CAED, LaCo(OH) x was converted to perovskite-type LCO during the SOFC startup.…”

“…[7,10,14,15] Here, we report at ailored SOFC cathode (LSM-YSZ) with high ORR activity at intermediate temperatures enabled by a new approach based on "electrochemical" surface modification. An electrochemical process is ap otentially powerful technique for surface modification with metal oxides, [14,[29][30][31][32] and in particular, we have recently demonstratedt he preparation of thin and conformal perovskite oxide coatings on metallics ubstrates by using af acile and cost-effective electrochemical method. [30][31][32] In this study,t he electrode surface of LSM-YSZ was modified with perovskite-type LaCoO 3 (LCO) nanoparticles by chemically assisted electrodeposition (CAED)c ombined with in situ thermal conversion during the SOFC startup.L CO was selected as as urfacem odifier because of its high catalytic and mixed ionic/electronic conducting properties.…”

“…An electrochemical process is ap otentially powerful technique for surface modification with metal oxides, [14,[29][30][31][32] and in particular, we have recently demonstratedt he preparation of thin and conformal perovskite oxide coatings on metallics ubstrates by using af acile and cost-effective electrochemical method. [30][31][32] In this study,t he electrode surface of LSM-YSZ was modified with perovskite-type LaCoO 3 (LCO) nanoparticles by chemically assisted electrodeposition (CAED)c ombined with in situ thermal conversion during the SOFC startup.L CO was selected as as urfacem odifier because of its high catalytic and mixed ionic/electronic conducting properties. [33][34][35][36] The proposed approach provides an easy and precise controlo ver the morphology of the LCO nanoparticles and their loading, withoutt he need for repeated deposition/annealing processes.…”