Study On Sr2MgMo_1-XV_XO_6-d Anode Materials For Solid Oxide Fuel Cells

Nowadays, double-perovskite structure Sr2MgMoO6(termed as:SMMO) materials is widely believed one of the the most promising anode materials for solid oxide fuel cells. But, in intermediate temperature range(500-700℃), its catalytic activity and electric conductivity is not good enough yet. Doping V is a possible way to improve those properties; but, no reports have been found so far on this kinds of researches.In this thesis, SMMO anode matreerials were firstly synthesized both in air and H2with citrate sol-gel method under different conditions. The effect of preparation conditions on the phase composition of the product was investigated, and the best conditions were found. Then, under the best conditions, the vanadium doped materials, Sr2MgMo1-xVxO6-d (termed as SMMVO, x=0,0.05,0.1,0.15,0.2), were synthesized. The synthesized samples were characterized by XRD, SEM, electroconductivity measurement and catalytic activity test for phase composition, morphology, electroconductivity, and catalytic activity for methanol oxidation. The main results are summarized as follows:1. The SMMO samples synthesized in air at each of the temperatures of1200℃,1300℃,1400℃, and1500℃for10h are mainly composed of double perovskite phase. Minors of impurity phases were observed, but synthesis in air at1400℃led to the least impurities. The samples synthesized in H2at1100℃for1to4periods (each period=24h) were also mainly composed of double perovskite phase. Synthesis in H2for2periods led to the least impurities. The electroconductivity of the samples synthesized in H2at1100℃for2periods was much higher than that synthesized in air at1400℃for10h. The SMMO samples synthesized in H2at1100℃for2periods showed a conductivity in H2of9.62S.cm-1at800℃, higher than that (8.60S.cm-1) reported by Huang et al in Science.2. All the Sr2MgMO1-xVxO6-d samples with x=0-0.2synthesized both in air and in H2under the best conditions were composed of almost pure double perovskite phase. The sample with x=0.05crystallized best. The sample with x=0.05synthesized in H2 showed the lowest conducting activation energy of8.7185kJ/mol, and showed higher electroconductivity in the lower temperature range.3. Both Sr2MgMoO6-d and Sr2MgMo0.95V0.05O6-d powder samples synthesized in air and H2under the best conditions showed narrow particle size distribution; but the samples synthesized in air showed larger particle size than those synthesized in H2. Both the samples are active for methanol oxidation, but Sr2MgMoo.95V0.0506-d showed much higher catalytic activity than Sr2MgMoO6-d-Since Sr2MgMoo.95V0.05O6-d material is of high electroconductivity and high catalytic activity for fuel oxidation in intermediate temperature range, it is possibly a very promising anode material for intermediate temperature solid oxide fuel cells. Most possibly, it is suitable for the H2S-containing fuels (such as, biogas etc.) because it contains V2O5, a sulfur-resistant catalyst.