The electrochemical performance of Ca 3 Co 4 O 9+δ (CCO) oxygen electrode with La 0.6 Sr 0.4 FeO 3-δ (LSF) interlayer in YSZ-based reversible solid oxide cells (RSOCs) was investigated in present work. Results proved that CCO oxygen electrode with LSF interlayer had a superior stability under alternating anodic and cathodic polarization . Both the polarization resistance and overpotential of the CCO electrode with LSF interlayer were significantly reduced compared to that with Ce 0.9 Gd 0.1 O 1.95 (GDC) interlayer, which confirmed the improvement of the redox reactivity of the oxygen electrode. The maximum power density of Ni-YSZ/YSZ/LSF/CCO fuel cell was 1276 mW cm −2 at 800 °C. An electrolysis current density of 1695 mA cm −2 was achieved at 1.5 V and 50% H 2 O. The hydrogen production rate of the electrolysis cell improved by 2 times than that with the GDC interlayer. Results made clear reliability of LSF as an interlayer in YSZ-based RSOCs.
Ca 3 Co 4 O 9+δ (CCO) cathode has been extensively studied for its excellent thermal expansion matching with commonly used electrolytes. CCO composite cathode with different concentrations of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 (LSGM) was prepared to evaluate its performance on LSGM electrolyte in this work. The appropriate amount of LaCoO 3 generated by the in-situ reaction of CCO and LSGM under operating conditions significantly enhances the oxygen exchange ability of CCO cathodes. The composite cathode containing 60 wt. % CCO and 40 wt. % LSGM (C-LGM60) exhibits the best electrochemical performance and the lowest polarization impedance among the C-LGM series cathodes. The area-specific resistance (ASR) of C-LGM60 is 0.06 Ωcm 2 at 750 °C. The maximal power density of the electrolyte-supported cell with C-LGM60 cathode reaches 489 mWcm -2 at 800 °C. After a 10 h stabilizing, there is no observable decline of the cell during the next 40 h of discharge. These results encourage the research of using CCO cathode on LSGM electrolytes and make valuable improvements on the development of SOFC cathode.
Chuangchuang Ruan,Hongzhang Song,Mengmeng Fan,Haoshan Hao,Shaohui Liu
Misfit-layered oxides Ca 3 Co 4 O 9+δ + z wt% SiC ( z = 0.00, 0.025, 0.05, 0.1, 0.2) samples were synthesized using solid-state sintering method and the effects of SiC nanoparticles diapersion on the thermoelectric properties were investigated. Thermoelectric properties of Ca 3 Co 4 O 9+δ + z wt% SiC ( z = 0.00, 0.025, 0.05, 0.1, 0.2) were investigated up to 923 K. Compared with pure sample, the electrical resistivity of SiC-added samples reduces, for Ca 3 Co 4 O 9+δ + z wt% SiC ( z = 0.00, 0.025, 0.05, 0.1, 0.2) ceramic samples with x ≤ 0.05, the electrical resistivity decreases with increasing SiC nanoparticles adding amounts. And, the electrical resistivity exists transition from semiconductor to metal conduction mechanism. While, the thermal conductivity also decreases due to the addition of SiC nanoparticles . As a result, the Ca 3 Co 4 O 9+δ + 0.2 wt% SiC sample had the lowest thermal conductivity of 1.47 W/Km at 923 K, which was 18.4% lower than that of the Ca 3 Co 4 O 9+δ sample. The ZT value of Ca 3 Co 4 O 9+δ + 0.05 wt% SiC can reach 0.218, which is 40.9% higher than the pure Ca 3 Co 4 O 9+δ sample.
Xueying Wu,Yanting Tian,Yongjia Zhang,Wei Guo,Yuan Li,Jiping Zhu,Lei Wang
Exsolution of active nanoparticles in oxide materials is an effective and feasible way to promote the catalytic activities of electrodes for solid oxide cells (SOCs). In this study, Ca-site deficient Ca x Co 4 O 9+δ (CCO-x, x = 1.5, 2, 2.5) materials are facilely prepared and studied as oxygen electrodes of SOCs. Co 3 O 4 nanoparticles are in-situ exsolved and well embedded on the Ca 3 Co 4 O 9+δ (CCO-3.0) surface by high-temperature annealing at 850 °C in ambient air. Results proves an effectively promotion of the ORR and OER kinetics with Ca deficiency. The polarization resistance of CCO-1.5 oxygen electrode reduces by 60% as compared with that of the CCO-3.0 electrode at 800 °C, from 0.23 to 0.09 Ω cm 2 . Both the peak power density and the electrolysis current density of the anode-supported SOC with CCO-1.5 oxygen electrode are more than 2 times that of the CCO-3.0 cell. The improved electrochemical kinetics is attributed to the exsolved Co 3 O 4 nanoparticles with high redox reactivity and the enhanced oxygen vacancy concentration. Results make clear reliability of Ca-site deficient Ca x Co 4 O 9+δ as a promisingly oxygen electrodes for SOCs.
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