Properties Of A Novel Bismuth Ion-doped Perovskite As SOFC Electrode Materials

In recent years,solid oxide fuel cells（SOFCs）have attracted extensive research and attention from all walks of life as efficient energy conversion devices.The device can directly convert the chemical energy of the fuel into electrical energy,and has the advantages of high fuel efficiency and environmental friendliness.SOFC fuel electrodes need to possess basic requirements such as high electronic and ionic conductivity,sufficient catalytic activity for fuel oxidation,chemical stability,and thermal expansion coefficient that match the adjacent components.Recently,in situ exsolution of perovskite surfaces has received considerable attention in the field of catalysis.The in-situ grown nanoparticles have good dispersibility,provide active sites for fuel oxidation,and enhance the catalytic activity of perovskite materials.A novel microstructure of double perovskite Sr Bi Fe Ti O_6–δ（SBFT）surface co-exsolution Bi-Fe nano-metallic particles was prepared by in situ reduction technology as the electrode material for SOFCs.Crystal structure studies found that the exsolution of metals Bi and Fe from the perovskite lattice under hydrogen（H₂）atmosphere did not change the cubic structure of SBFT perovskites.The conductivity results show that the exsolved nanoparticles effectively enhance the conductivity of the samples.XPS results show that the reduced SBFT surface has Ti^3+/4+,Fe^3+/2+/0,Bi^3+/0,and Sr²⁺valence states.The output peak power densities of a single cell with SBFT–Ce_0.8Sm_0.2O_1.9 as an anode are 280 and 503 m W cm^-2 in ethanol and under a H₂atmosphere at 800°C respectively.In ethanol at 800°C the fuel cell is relatively stable for over 30 h under a voltage of 0.5 V.The double perovskite Sr_2-xBi_xFe_1.5Mo_0.5O_6-δ（x=0-0.2;SBFM）electrode material was synthesized by the solid-phase method.The Sr_1.9Bi_0.1Fe_1.5Mo_0.5O_6-δ（SBFM01）electrode material can exsolved metal nanoparticles under reducing atmosphere,and can be re-oxidized to become pure phase.The SBFM01 electrode material has good chemical compatibility with both LSGM and SDC electrolytes under different atmospheres.In the air and hydrogen atmosphere at 800 ^oC,the polarization impedance values of SBFM01 are 0.266Ωcm² and0.310Ωcm²,respectively.The maximum output power density of the symmetric cell fueled by H₂ at 800 ^oC is 482.9 m W cm^-2.The single cell with SBFM01 as the anode achieves a maximum output power density of 210.5 m W cm^-2 at 800 ^oC with ethanol as fuel.In addition,the SBFM01-SDC（6:4）composite electrode exhibited good CO₂ electrolysis performance and electrochemical stability in solid oxide electrolysis cell（SOEC）mode.The Pr_1-xBi_xFe O_3-δ（x=0.1-0.2;PBF）perovskite electrode material was designed and prepared by the solid-phase method.After high temperature reduction,it was decomposed into the main phase of PBF,and the composite structure of metal Bi,Fe and Pr₂O₃nanoparticles.The electrode materials have good chemical compatibility with SDC and LSGM electrolytes in air or reducing atmosphere.XPS results show that the metal cations on the surface of the reduced electrode material have valence states of Pr^3+/4+,Fe^3+/2+/0 and Bi^3+/0.The electrical conductivity test results show that the exsolved metal nanoparticles and Pr₂O₃are beneficial to improve the electrical conductivity of the electrode material under the hydrogen atmosphere.Electrochemical impedance test shows that the substitution of Bi element for Pr element can improve the electrochemical performance of the electrode material and reduce the polarization resistance.The single cell with PBF02 as anode achieves a maximum power density of 337.9 m W cm^-2 at 800 ^oC with ethanol as fuel,and exhibits good electrochemical stability in stability tests.