尖晶石结构反转提高氧还原催化活性的密度泛函研究

发布时间：2018-02-22 00:55

本文关键词： 尖晶石氧还原反应异化效应密度泛函理论吉布斯自由能图　出处：《中国科学:化学》2017年07期 　论文类型：期刊论文

【摘要】：基于实验发现尖晶石型催化剂晶体结构的反转会使其对氧还原反应(ORR)的催化活性显著提高,本文通过密度泛函理论(DFT)计算方法探究了尖晶石(Co_3O_4)-反尖晶石(Co_2FeO_4)-尖晶石(CoFe_2O_4、Fe_3O_4)的结构反转对氧还原催化活性提高的本质.计算发现,随着尖晶石结构的反转,反尖晶石带隙收窄,导电性增强;费米能级按"尖晶石(Co_3O_4)反尖晶石(Co_2FeO_4)尖晶石(CoFe_2O_4、Fe_3O_4)"的次序依次降低,氧还原第一步电子转移能力逐渐变弱.此外,由于反尖晶石Co_2FeO_4八面体占位,Fe、Co原子间的异化效应使O O键的活化程度最为显著.氧还原吉布斯自由能表明,若各催化剂电子传输能力相同,则反尖晶石Co_2FeO_4与尖晶石Co_3O_4较尖晶石CoFe_2O_4和Fe_3O_4更利于OH的脱附.综合分析表明,反尖晶石Co_2FeO_4平衡了掺杂前后尖晶石催化剂的导电性、第一步电子转移能力、对O_2的活化和OH的脱附能力,呈现出最优的ORR催化活性.
[Abstract]:Based on the experimental results, it was found that the inversion of the crystal structure of spinel catalyst could significantly increase its catalytic activity for oxygen reduction reaction (ORR). By means of density functional theory (DFT) calculation, this paper explores the nature of the increase in catalytic activity for oxygen reduction of the structure inversion of the spinel Co3O4T / Co2FeO4C _ 2FeO _ 4 / S _ S _ 2FeO _ 4). It is found that with the inversion of the structure of the spinel, the stripe gap of the antispinel becomes narrower, and the structure inversion of the structure of the spinel CoFe2O4Fe3O4O4) increases the catalytic activity of oxygen reduction. The Fermi level decreased in the order of "spinel Cos _ 3O _ 4) anti-spinel Co2FeO _ 4) spinel CoFe2O4T _ 3O _ 4) and the first-step electron transfer capacity of oxygen reduction gradually weakened. Because of the dissimilation effect among the octahedron of Co_2FeO_4 octahedron, the activation of O / O bond is the most obvious. The Gibbs free energy of oxygen reduction shows that the electron transport capacity of the catalysts is the same. The desorption of OH by invert spinel Co_2FeO_4 and spinel Co_3O_4 is more favorable than that of spinel CoFe_2O_4 and Fe_3O_4. The comprehensive analysis shows that antispinel Co_2FeO_4 balances the conductivity of spinel catalyst before and after doping, and the first step electron transfer ability is obtained. The activation of O _ 2 and the desorption of OH showed the best ORR catalytic activity.
【作者单位】：重庆大学化学化工学院;
【基金】：国家自然科学基金(编号:21376284,21436003)资助项目
【分类号】：O643.36;TM911.4

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