Sr_(0.95)Sc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)负载Ag^(0)复合阴极的原位脱溶制备及性能

In Situ Exsolution of Sr_(0.95)Sc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)-Ag^(0) Composite Cathode for Proton-Conducting Solid Oxide Fuel Cell

本文首先采用溶胶-凝胶法合成出Ag0.05Sr_(0.95)Sc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)(S_(0.95)SNC-Ag^(+))钙钛矿型氧化物,然后利用1%H2O-O2(体积分数)气氛对其进行原位脱溶,制备出Sr_(0.95)Sc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)负载Ag0纳米颗粒(S_(0.95)SNC-Ag0)的复合阴极,并考察其作为质子导体固体氧化物燃料电池(H^(+)-SOFC)阴极材料时的电化学性能。通过X射线衍射(XRD)、直流四端子法、X射线光电子能谱(XPS)对原位脱溶前后材料的晶体结构转变、电导率变化、元素价态升降及其他性质的改变进行研究。进一步制备S_(0.95)SNC-Ag0/BaZr_(0.1)Ce_(0.7)Y_(0.2)O_(3-δ)(BZCY)/S_(0.95)SNC-Ag0对称电池,研究了S_(0.95)SNC-Ag0作为H^(+)-SOFC阴极的电化学性能,同时组装S_(0.95)SNC-Ag0/BZCY/NiO+BZCY单电池,测试单电池的性能输出。研究结果表明,原位脱溶产生的Ag0促进了阴极的氧吸附解离步骤;经原位脱溶处理后单电池在600℃下的最大功率密度由332提升至351 mW·cm^(-2)。

With the aggravation of global warming trend,people have formed a consensus on the use of clean energy,and the de‐mand is increasingly urgent and vigorous.Solid oxide fuel cell (SOFC) is an efficient,environmentally friendly and mature technology to directly convert hydrogen energy into electric energy.Proton-conducting solid oxide fuel cells (H+-SOFCs) can operate at medium and low temperature (400~600℃),producing water at the cathode.Until now,H+-SOFC has two problems:(1) Poor stability limited by the lack of active sites for cathodic oxygen reduction reaction (ORR).(2) The catalytic activity of cathode material for ORR reac‐tion is insufficient.In this paper,Ag0.05Sr_(0.95)Sc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)(S0.95SNC-Ag+) perovskite oxide was prepared by sol-gel method.The composite cathode of Sr_(0.95)Sc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)loaded Ag^(0) (S0.95SNC-Ag^(0)) was obtained through in situ exsolution S0.95SNC-Ag+in 1% H2O-O2(volume fraction) atmosphere at 600℃.The solid electrolyte BaZr0.1Ce0.7Y0.2O3-δ(BZCY) was prepared using the same method.The transformation of crystal structure,the changes of electrical conductivity,element valence and other properties before and after in situ exsolution were investigated by X-ray diffraction (XRD),direct current four-terminal method and X-ray photoelectron spectroscopy (XPS).S0.95SNC-Ag^(0)/BZCY/S_(0.95)SNC-Ag^(0) symmetrical cell and S0.95SNC-Ag^(0)/BZCY/NiO+BZCY single cell were fabricated and their electrochemical properties were investigated.The symmetrical cell was passed through 1% H_(2)O-O_(2) atmosphere for 16 h to ex‐plore the effect of in situ exsolution on the polarization process of S_(0.95)SNC-Ag^(0) cathode.The current density of 625 mW·cm-2was main‐tained at both ends of the single cell for 16 h for in-situ exsolution occurred in the cathode,and the variation of working voltage of the single cell was tested.Then current-voltage (I-V) curve of the single cell was tested again.The cross section of single cell and energy dispersive X-ray spectroscopy (EDS)-mapping of S_(0.95)SNC-Ag^(0) were captured by scanning electron microscope (SEM).The interplanar spacing of Ag^(0) nanoparticles was obtained by high-resolution transmission microscope (HRTEM) images.XRD results showed that S_(0.95)SNC-Ag+presented a perovskite structure.XPS results showed that Ag 3d peak of S_(0.95)SNC-Ag^(0) was shifted to a larger binding ener‐gy than that of S_(0.95)SNC-Ag^(+).This indicated that Ag^(0) appeared after in situ exsolution treatment.The thermal expansion coefficient of S0.95SNC-Ag+was smaller than that of SrSc_(0.175)Nb_(0.025)Co_(0.8)O_(3-δ)(SSNC),indicating that S_(0.95)SNC-Ag^(+)had better thermal matching with BZ‐CY than that of SSNC.The results of the conductivity test demonstrated that S0.95SNC-Ag+had a greater conductivity than SSNC under ordinary air conditions.With the prolongation of the in situ exsolution time,the conductivity of S_(0.95)SNC-Ag^(0) increased gradually.The test results of symmetric cells presented that in situ exsolution reduced the impedance resistance of the oxygen adsorption and dissocia‐tion step on the cathode,but not for the gas diffusion step.And the ohmic impedance of S_(0.95)SNC-Ag^(0) cathode was significantly smaller than that of SSNC cathode with the same electrolyte,suggesting that S0.95SNC-Ag^(0) would have a higher power density.The single-cell test results showed the single cell with S_(0.95)SNC-Ag^(0) as the cathode delivered a higher powder density than that with SSNC as cathode.With the prolongation of the in situ exsolution time,the working voltage of the single cell continued to increase,and the power density of S_(0.95)SNC-Ag^(0)/BZCY/NiO+BZCY single cell increased from 332 to 351 mW·cm^(-2)at 600℃.These results demonstrated that in situ ex‐solution was a powerful technique to prepare a composite cathode of perovskite loaded metal nanoparticles,and the prepared S_(0.95)SNC-Ag^(0) was a potential cathode for H+SOFC.