Performance Of La, Cr Co-doped SrTiO3Perovskite As Anode Material

It is great significance of solving energy and environmental issues thatresearching and development solid oxide fuel cell （SOFC）.Ni/YSZ（yttria stabilizedzirconia） is a very much favored ceramic anode material. This material showesexcellent performance and stability when the fuel was H2. However when usecheaper hydrocarbons as fuel, there will be make carbon deposition due to catalysisof Ni/YSZ anode on hydrocarbons. If the fuel contain sulfur （such as coal, naturalgas）, the anode may sulfur poisoning. In addition, Ni/YSZ anode’s stability may beaffected due to Ni reunion because of long time operating at high temperature. In theoxidation atmosphere, Ni will oxidized to NiO, leading to damage to the structure ofanode. So researching and development anode materials which can operate inhydrocarbons atmosphere and oxidation atmosphere long time is the key problem toreduce running cost and promote SOFC application.In the paper, we study on SrTiO₃-based amode material, using La and Crrespectively replace Sr and Ti. The La content is fixed at0.3and change Cr contentat the same time. We successfully synthesized La_0.3Sr_0.7Cr_xTi_1-xO₃（x=0,0.05,0.10,0.15, respectively, named LSCTO00or LSTO, LSCTO05, LSCTO10LSCTO15）new anode materials （referred to as LSCTO） using conventional solid phase methodin the closed furnace tube which use activated carbon manufacturing reducingatmosphere, and the performance of this materials was tested. The study found thatthe coefficient of thermal expansion of the LSCTO material is very close to YSZ’S.The high temperature conductivity test results show that the pure SrTiO₃conductivity is very small. The conductivity is smaller10S·cm^-1 in the reducingatmosphere at700℃. The conductivity of La_0.3Sr_0.7TiO₃is366.2S·cm^-1at700℃inthe same atmosphere. The electrical conductivity of the material is slightly reducedwhen doped Cr, but still state high level. The electrical conductivity respectivelyachieve325S·cm^-1、337.4S·cm^-1and260.7S·cm^-1with increasing Cr content.From the investigation of thermal stability and oxidation reducing stability ofthe LSCTO materials, we found that the LSTO’s is better. In hydrogen atmosphereand constant temperature of700℃, the conductivity of LSTO don’t appearattenuation. After four time oxidation-reduction cycle testing, the conductivityreaches to84.1%of formal and gradually stabilized. The LSCTO10material reachesto97.8%, which explain the LSCTO’s oxidation reducing stability is better.In the preparation process, we use Chemical vapor deposition method to deposition Fe on the material surface. The electrical conductivity of the materialfurther improved because of generating FeCr2O4. The conductivity of LSCTO05achieve399.1Scm^-1in hydrogen atmosphere at700℃after chemical vapordeposition. The conductivity increased by22.8%, indicating that this approach helpsto improve the conductivity of the material.We make the pure LSCTO anode and YSZ as half-cell, doing the ACimpedance spectra test both in H2and CH4atmosphere, founding that thepolarization resistance in H2is better than in CH4at750℃. UsingLSCTO（00/05/10/15） anode, YSZ electrolyte, Ag cathode to assemble single cell,the polarization resistance of the battery decreases with increasing Cr dopingcontent, indicating doped Cr improve the catalytic activity of the material LSCTO.The maximum power density respectively achieve6.05mW·cm^-2、10.33mW·cm^-2、51.79mW·cm^-2、57.50mW·cm^-2The LSCTO anode material with dipping Ni of LSCTO get good outputperformance. The maximum power density of battery with LSCTO00achieve181.51mW·cm^-2, nearly30times higher than the original battery. The single cellusing LSM oxide cathode was significantly superior to the Ag electrode single cell.We use Ni and SDC dipping LSCTO materials in order to improve the outputperformance. The maximum power density of single cell,Ni-SDC-LSCTO（05/10/15）/YSZ/LSM, respectively achieve355.5mW·cm^-2、411.3mW·cm^-2、424.7mW·cm^-2, which respectively increase by28%、20%、19%compared with simply impregnated Ni batteries. Thus Ni and SDC impregnation isan effective way to improve LSCTO electrode material propertiesIn the summary, the La0.3Sr0.7CrxTi1-xO₃has high conductivity and goodoxidation-reduction cycle stability. After dipping Ni and SDC can improve theelectrochemical properties significantly, expected substitution of Ni/YSZ in SOFCto be widely used.