【作者】 周鑫；

【导师】 赵宜成； 李永丹；

【作者基本信息】 天津大学 ， 化学工程与技术， 2021， 硕士

【摘要】 作为一种清洁且高效的发电装置,固体氧化物燃料电池（SOFC）对于缓解能源危机与环境污染问题有重要现实意义,然而较高的操作温度是阻碍其实际商业化应用的关键因素之一。由于质子迁移的活化能较低,质子传导型SOFC（H-SOFC）比氧离子传导型SOFC（O-SOFC）更适合于低温操作,但较大的阴极极化电阻使得目前H-SOFC的发展相对滞后,因此亟需开发适用于H-SOFC的阴极材料。为开发出具有应用潜力的高性能H-SOFC无钴阴极材料,本文围绕BaCe_xFe_1-xO_3-δ-基钙钛矿材料氧还原活性的提高进行了研究工作。制备了BaCe_0.2Fe_0.6Gd_0.15X_0.05O_3-δ（X=Mo、Cu、In、Gd）阴极材料,分析了各材料的晶体结构、电导率、电导弛豫行为和催化活性等性质。Mo和In的掺杂维持了BaCe_0.2Fe_0.6Gd_0.2O_3-δ材料的BaFe O_3-δ相。Cu的掺杂导致了正交钙钛矿出现,并使得BaFe O_3-δ相最接近于立方结构。Mo和Cu掺杂显著提高了阴极材料的电导率和氧催化活性。以BaCe_0.2Fe_0.6Gd_0.15Cu_0.05O_3-δ-BaZr_0.1Ce_0.7Y_0.2O_3-δ为阴极,50μm厚的BaZr_0.1Ce_0.7Y_0.2O_3-δ为电解质层的单电池在700 ^°C时的最大功率密度(P_max)为396 m W cm^-2,说明Cu掺杂的BaCe_0.2Fe_0.6Gd_0.2O_3-δ具有作为阴极材料的潜力。研究了Pr掺杂的H-SOFC阴极材料BaCe_0.2Fe_0.8-xPr_xO_3-δ（x=0、0.1、0.2、0.3）。各材料由立方型BaFe O_3-δ相和正交型BaCe O_3-δ相组成,Pr掺杂降低了BaFe O_3-δ相的含量,从而导致了电导率的降低。BaCe_0.2Fe_0.6Pr_0.2O_3-δ(BCFP_0.2)表面的吸附氧和低价铁离子含量最多,因而具有最高的氧表面交换系数和最高的阴极活性。550 ^°C时水分压对阴极的极化电阻（R_p）的影响可忽略不计,但氧分压的降低导致R_p显著增加,表明阴极的速率控制步骤为氧表面交换过程。700 ^°C时,BCFP_0.2具有最低的R_p值0.057Ωcm²,在该温度下,以其为阴极的单电池的P_max为562 m W cm^-2,表明BCFP_0.2是一种有前景的H-SOFC无钴阴极材料。更多还原

【Abstract】 As a clean and efficient power generation device,solid oxide fuel cell（SOFC）is of great importance to alleviate the energy crisis and environmental pollution problems.However,the high operating temperature is one of the key factors hindering its practical commercial application.Due to the lower activation energy of proton transfer,proton-conducting SOFC（H-SOFC）is more suitable for low temperature operation than oxygen ion conducting SOFC（O-SOFC）,but the larger cathodic polarization resistance limits the current development of H-SOFC.Therefore,developing cathode materials for H-SOFC is urgent.In order to develop practical and high-performance cobalt-free cathodes,this work mainly focuses on the optimization of BaCe_xFe_1-xO_3-δ-based materials to improve their oxygen reduction reaction activity.BaCe_0.2Fe_0.6Gd_0.15X_0.05O_3-δ（X=Mo,Cu,In,Gd）cathode materials are synthesized.Their porperties including cystal structure,electrical conductivity,electrical conductivity relaxation behavior and catalytic activity are studied.The BaFe O_3-δphase of BaCe_0.2Fe_0.6Gd_0.2O_3-δis maintained with the doping of Mo and In,while the doping of Cu brings an orthorhombic perovskite phase and makes the BaFe O_3-δphase closest to its cubic structure.Mo and Cu doping significantly increase the electrical conductivity and the oxygen activity of BaCe_0.2Fe_0.6Gd_0.2O_3-δ.A single cell with BaCe_0.2Fe_0.6Gd_0.15Cu_0.05O_3-δ-BaZr_0.1Ce_0.7Y_0.2O_3-δcathode and a 50μm-thick BaZr_0.1Ce_0.7Y_0.2O_3-δelectrolyte layer shows the highest maximum power density(P_max)of 396 m W cm^-2 at 700 ^°C,indicating that Cu doped BaCe_0.2Fe_0.6Gd_0.2O_3-δis a potential cobalt-free cathode for H-SOFC.BaCe_0.2Fe_0.8-xPr_xO_3-δ（x=0,0.1,0.2,0.3）are studied as cobalt-free cathode materials for H-SOFC.They are composed of cubic BaFe O_3-δand orthorhombic BaCe O_3-δphases,and Pr is doped in both phases.The partial substitution of Pr for Fe decreases the content of the BaFe O_3-δphase,leading to a lower electrical conductivity.BaCe_0.2Fe_0.6Pr_0.2O_3-δ(BCFP_0.2)has the most adsorbed oxygen and Fe³⁺on the surface,resulting in the fastest oxygen surface exchange kinetics and the highest activity.The partial pressure of H₂O shows a negligible effect on the polarization resistance（R_p）of the cathode.In contrast,the R_p increases remarkably with the decrease of oxygen partial pressure,indicating that the rate of the cathode process is controlled by the surface exchange of oxygen.At 700 ^°C,BCFP_0.2shows the lowest R_p of 0.057Ωcm²,and a single cell with that cathode exhibits the highest P_max of 562 m W cm^-2.The results demonstrate that BCFP_0.2 is a promising cobalt-free cathode material for H-SOFC.更多还原