Preparation And Electrochemical Performance Of Mixed-conducting Cathode Materials For Protonic Ceramic Fuel Cells

As an efficient and clean energy conversion device,solid oxide fuel cell?SOFC?has great development prospects.In order to make it commercially competitive,lowering the operating temperature is the key.Reducing the operating temperature can not only save the cost of SOFC materials and related supporting facilities,but also significantly extend the service life of the materials.Compared with oxygen-ion conducting solid oxide fuel cell(O^2--SOFC),proton-conducting solid oxide fuel cell?H⁺-SOFC?can adapt to lower operating temperature,have lower activation energy,and higher battery effectiveness.Therefore,the development of H⁺-SOFC at low and medium temperatures has received more attention and research.This study focuses on the development and characterization of a series of new perovskite?ABO₃?-type mixed-conducting cathode materials for proton conductor solid oxide fuel cells.Based on the idea of mixed conductivity,this study successfully developed Ba_0.95La_0.05Fe_0.8Zn_0.2O_3-??BLFZ?triple mixed conductor?proton-oxygen ion-electron?cathode material by doping the B site of perovskite with metal ions.At the same time,Ba Co_0.6Ce_0.2Y_0.1Yb_0.1O_3-??BCCYYb0.6?triple mixed conductor composite cathode material was developed by compounding different conductive materials.X Ray Diffraction?XRD?,field emission scanning electron microscope?FE-SEM?,field emission transmission electron microscope?TEM?,thermal gravimetric analysis?TG?and oxygen non-stoichiometry were used to study the microscopic morphology and phase composition of the cathode powders.The electrochemical properties of BLFZ and BCCYYb0.6 materials were studied by impedance analysis and current-voltage polarization.The specific research results are as follows:?1?Based on the Ba_0.95La_0.05Fe O_3-?material,a certain amount of Zn was doped at the B site to successfully synthesize the triple mixed conducting material BLFZ,and the cubic perovskite structure was obtained.Symmetrical cells with Ba Zr_0.1Ce_0.7Y_0.1Yb_0.1O_3-??BZCYYb?as the electrolyte and BLFZ as the electrode have a polarization resistance of0.18?cm^-2in an anhydrous environment at 650? test temperature.And them polarization resistance is 0.10?cm²in an environment containing 3%water.The single cell with Ni O and BZCYYb composite material as the anode,BZCYYb as the electrolyte and BLFZ as the cathode has a peak power density of 950 m W cm²when the test temperature is 650?.In the long-term stability test,under the condition of a test temperature of 600? and a constant current density of 600 m A cm^-2,the single cell has been operating at a stable state with a high voltage of 0.7 V and a stable operating time of 46 h.The above results strongly suggest that BLFZ exhibits an excellent electrochemical performance as an oxygen reduction electrode for H+-SOFC.?2?The two-phase composite BCCYYb0.6 was synthesized by the sol-gel one-step method,which self-assembled into two-phase distributed material when sintered at high temperature.XRD analysis initially verified the correctness of the design ideas.The symmetrical cell with BZCYYb as the electrolyte and BCCYYb0.6 as the cathode has a polarization resistance of 0.31?cm²in an anhydrous environment and a 0.09?cm²in an environment containing 3%water,respectively,at a test temperature of 650?.