不同方法制备PrNi_(0.5)Co_(0.5)O_(3-δ)阴极的性能对比研究

Comparative Study on Properties of PrNi_(0.5)Co_(0.5)O_(3-δ) Cathode Prepared by Different Methods

采用固相反应法和乙二胺四乙酸-柠檬酸(EDTA-CA)联合络合法分别合成了PrNi_(0.5)Co_(0.5)O_(3-δ) (PNC)材料,用于质子导体固体氧化物燃料电池(H-SOFCs)的阴极。通过X射线衍射(XRD)研究了材料在不同煅烧条件后的相结构,通过比表面积及孔径分析仪(BET)研究材料的比表面积和孔结构,用扫描电子显微镜(SEM)观察了材料的微观结构,通过能量色散X射线谱仪(EDS)分析材料的元素分布,通过电化学阻抗谱(EIS)分析了材料作为H-SOFCs阴极使用时的极化电阻。结果表明,通过EDTA-CA联合络合法制备的粉体相结构更加稳定,且元素分布也更加均匀。EIS分析结果表明,通过两种方法制备的阴极材料在BaZr_(0.1)Ce_(0.7)Y_(0.1)Yb_(0.1)O_(3-δ)(BZCYYb)电解质上的氧还原过程活化能相近,但通过EDTA-CA联合络合法制备的阴极具有更低的极化电阻,500℃时对称电池上的极化电阻降低68%。

As an efficient energy conversion device, fuel cell can efficiently convert the chemical energy of fuel into electricity at operating temperature which is an ideal power generation technology for carbon neutral society. Unlike other fuel cells, solid oxide fuel cells(SOFCs) operate at relatively high temperatures and do not use noble metal materials for electrodes, which greatly reduces the cost of fuel cells. At the same time, SOFCs also have the advantages of fuel flexibility, and gas, liquid and even solid fuels can generate electricity in SOFCs. SOFCs can be mainly divided into oxygen oxygen-ion conducting solid oxide fuel cells(O-SOFCs) and proton conducting solid oxide fuel cells(H-SOFCs) according to the conduction mechanism of the electrolyte. Since the activation energy of proton conduction is lower than that of oxygen-ion, H-SOFCs can work at relatively lower operating temperatures(400~700 ℃). The reduction of working temperature reduces the difficulty in sealing and thermal management of SOFCs, which facilitates their application. However, as the operating temperature decreases, the oxygen reduction process at the cathode of SOFCs becomes more difficult, and the increase in the resistance of the cathode directly affects the output performance of the fuel cell. The development of high-performance cathodes suitable for use in mid-low temperature SOFCs has become a current research hotspot. In recent years, the use of triple conducting cathodes(TCCs) in H-SOFCs has received more attention and research. Theses cathodes can conduct protons, oxygen ions and electrons(H^(+)/O_(2)^(-)/e^(-)) at the same time, which extending the reaction interface of the cathode process to the entire cathode surface and interior and greatly improving the efficiency of the cathode reaction process. At present, the mechanical mixing of multiphase materials, the one-step synthesis of multiphase nanocomposites, and solution impregnation can be used to design TCC cathodes, and the study of achieving triple conductivity through a single structural material has received attention because of its simple material composition. In this study, PrNi_(0.5)Co_(0.5)O_(3-δ)(PNC) materials for H-SOFCs were synthesized by solid-phase reaction method and ethylenediaminetetraacetic acid-citric acid(EDTA-CA) combined complexation method, respectively. The phase structure of the material after different calcination conditions was studied by X-ray diffraction(XRD), the specific surface area and pore structure of the material were studied by specific surface area and pore size analyzer(BET), and the microstructure of the material was observed by scanning electron microscope(SEM). The elemental distribution of the material was analyzed by energy dispersive X-ray spectrometer(EDS), and the polarization resistance of the material when used as the cathode of H-SOFCs was analyzed by electrochemical impedance spectroscopy(EIS). The results showed that the powder phase structure prepared by EDTA-CA combined complex method was more stable and the element distribution is more uniform. EIS analysis results showed that the activation energies of the oxygen reduction reaction(ORR) process on the BaZr_(0.1)Ce_(0.7)Y_(0.1)Yb_(0.1)O_(3-δ)(BZCYYb) electrolyte were similar for the cathode materials prepared by the two methods, but the cathode prepared by EDTA-CA combined complexation method had lower polarization resistance. Although the polarization resistance of the powder synthesized by the solid-state reaction method was relatively large, the preparation process was relatively simple, and it could also be used for the synthesis of cathode materials by optimizing the mixing and sintering conditions of the powder fabrication.