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DFT study of difference caused by catalyst supports in Pt and Pd catalysis of oxygen reduction reaction

查看全文 作　　者：LI [1,2,3]Li;WEI [1,2,4]ZiDong;ZHANG [4]Yi;QI [2,4]XueQiang;XIA [4]MeiRong;ZHANG [2]Jie;SHAO [5]ZhiGang;SUN [1]CaiXin 高影响力作者 机构地区：[1]State Key Laboratory of Power Transmission Equipment&System Security and New Technology,Chongqing University,Chongqing 400044,China;[2]School of Material Science and Engineering,Chongqing University,Chongqing 400044,China;[3]School of Chemistry and Chemical Engineering,China West Normal University,Nanchong 637002,China;[4]School of Chemistry and Chemical Engineering,Chongqing University,Chongqing 400044,China;[5]Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,China高影响力机构 出　　处：《Science China Chemistry》索引2009年第52卷第5期,共8页高影响力期刊 基　　金：Supported by the National Natural Science Foundation of China (Grant No. 20676156);the Chinese Ministry of Education (Grant No. 307021);the National 863 Program (Grant Nos. 2006AA11A141 and 2007AA05Z124);the Chongqing Sci &Tech Key Project (Grant No. CSTC2007AB6012) 摘　　要：Based on an experimental phenomenon that catalytic activity of Pt and Pd for oxygen reduction reaction (ORR) changes with catalyst supports from C to TiO2, density function theory (DFT) was used to elucidate the cause behind the difference in catalysis caused by catalyst supports. First, factors closely associated with the first electron transfer of the ORR were assessed in the light of quantum chemistry. Then intermediate (atomic oxygen, O) adsorption strength on the catalyst surface was calculated. The results show that, in terms of minimum energy difference, the best orbital symmetry match, and the maximum orbital overlap, TiO2 does bring about a very positive effect on catalysts Pd/TiO2 for the first electron transfer of the ORR. Especially, TiO2 remarkably expands the space size of Pd/TiO2 HOMO orbital and improves orbital overlap of Pd/TiO2 HOMO and O2 LUMO. The analysis of deformation density and partial density of state shows that the strong interaction between Pt and Ti leads to a strong adsorption of intermediate O on Pt/TiO2, but the strong interaction between Pd and surface O causes positive net charge of Pd and a weak adsorption of intermediate O on Pd/TiO2. Thus, the ORR can proceed more smoothly on Pd/TiO2 than Pt/TiO2 in every respect of maximum orbital overlap and rate delay by intermediate O. The research also discloses that several factors lead to less activity of TiO2-supported Pt and Pd catalysts than the C-supported ones for the ORR. These factors include the poor dispersion of Pt and Pd particles on TiO2, poor electric conduction of TiO2 carrier itself, and bigger energy difference between HOMO of TiO2-carried metallic catalysts and LUMO of O2 molecule due to electrons deeply embedded in the semiconductor TiO2 carrier. 关 键 词：density function theory (DFT) catalyst-support interaction ELECTROCATALYSIS oxygen reduction reaction (ORR) carbon TiO2
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