Slow oxygen reduction reaction (ORR) involving proton transport remains the limiting factor for electrochemical performance of proton-conducting cathodes. To further reduce the operating temperature of protonic ceramic fuel cells (PCFCs), developing triple-conducting cathodes with excellent electrochemical performance is required. In this study, K-doped BaCo 0.4 Fe 0.4 Zr 0.2 O 3− δ (BCFZ442) series were developed and used as the cathodes of the PCFCs, and their crystal structure, conductivity, hydration capability, and electrochemical performance were characterized in detail. Among them, Ba 0.9 K 0.1 Co 0.4 Fe 0.4 Zr 0.2 O 3− δ (K10) cathode has the best electrochemical performance, which can be attributed to its high electron (e − )/oxygen ion (O 2− )/H + conductivity and proton uptake capacity. At 750 °C, the polarization resistance of the K10 cathode is only 0.009 Ω·cm 2 , the peak power density (PPD) of the single cell with the K10 cathode is close to 1 Wcm −2 , and there is no significant degradation within 150 h. Excellent electrochemical performance and durability make K10 a promising cathode material for the PCFCs. This work can provide a guidance for further improving the proton transport capability of the triple-conducting oxides, which is of great significance for developing the PCFC cathodes with excellent electrochemical performance.
Ruineng Ruan,Haibo Xiao,Wenjing Dong,Zhanghong Yu,Xunying Wang,Baoyuan Wang,Chen Xia,Hao Wang
Fast ionic transportation is in high demand for developing low-temperature solid oxide fuel cells (LT-SOFCs). Facing this challenge, a new H + /O 2− /Li + triple conductor is designed in this study from a lithium-metal oxide, spinel Li 4 Ti 5 O 12 (LTO). First-principle calculation based on density functional theory (DFT) reveals the proton transport barrier in LTO can be as low as 0.37 eV while the barrier for oxygen ion transportation is 0.94 eV. Using the designed LTO as the electrolyte and a typical cathode of lithium-ion battery, LiNi 0.8 Co 0.15 Al 0.05 O 2-δ , as the symmetrical electrodes, an all-lithium-metal-oxides-based LT-SOFC is constructed. High performance is achieved by the SOFC at 550–425 °C, i.e. 625 mW cm −2 at 550 °C, and a low activation energy of 0.60 eV is found with respect to the ionic conductivity of LTO at 550–475 °C. Further study confirms the dual O 2− /H + conduction of LTO via the application of proton and oxygen ion filters as well as the transference number test. Additionally, particular attentions are paid to the transport behavior of Li + in the cell via a charging process study and from XRD results. The possible contribution of triple conduction on fuel cell performance is discussed. This work demonstrates the great promise of triple H + /O 2− /Li + conducting lithium-metal oxides for LT-SOFC electrolyte development.
Selective catalytic reduction (SCR) utilizing urea hydrolysis to generate ammonia (NH 3 ) is the most efficient technology to reduce the emission of nitrogen oxides (NO x ). NH 3 detection is crucial in the closed-loop feedback system for the precise urea injection. In this work, a high-temperature NH 3 sensor using a BaZr 0.8 Y 0.2 O 3-δ (BZY) proton conductor as the electrolyte and a BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ (BCFZY) H + /e – /O 2– triple conductor as the sensing electrode (SE) is reported. The effect of the micromorphology of the BCFZY SE on the sensing performance is investigated by varying the sintering temperature of SE. The sensor shows high sensitivity to NH 3 with response currents of 0.39, 1.31, 3.03, and 1.81 μA/ppm at 350, 400, 450, and 500 °C, respectively. Furthermore, the sensor shows excellent selectivity and repeatability. This work demonstrates that the BCFZY based sensor has great potential for the high-temperature NH 3 detection.
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