摘要
针对聚苯胺(PANI)包覆Pt/C催化剂以后,形成的Pt/C@PANI核壳结构催化剂稳定性和催化氧还原活性显著提高的现象,采用密度泛函方法从理论角度研究了其稳定性和催化活性提高的原因.结果发现,随着PANI将电子转移给载体C,自身空穴增加,PANI部分氧化,导电性增强;PANI在Pt/C表面主要通过共轭苯环的形式(3C、N2C-I)相互作用且伴随着电子转移;PANI的存在使Pt/C@PANI体系的HOMO能级升高,减小了与氧气分子LUMO能级的差异,有利于电子从催化剂HOMO转移到氧分子的LUMO轨道,使得氧容易得到电子;PANI吸附后,Pt原子d带中心显著降低,利于中间物种的脱附,催化活性更高;分态密度表明,PANI使Pt、C均向低能级方向移动,使Pt/C体系更稳定.
The stability and catalytic oxygen reduction activity of platinum/carbon （Pt/C） catalyst were greatly enhanced after covered with polyaniline （PANI）, and density functional theory calculations were carried out to investigate the essential reasons behind this phenomenon in present work. The theoretical calculations disclosed that the number of holes in PANI increased with the electrons transfer from PANI to support C, which caused partial oxidation of PANI and thus strengthened the electric conductivity of PANI. PANI interacted with Pt/C mainly via three C atoms or one N atom and two C atoms within the same benzene ring. The system energy decreased markedly with the coverage of PANI on the Pt/C, which meant that the Pt/C@PANI was more stable than Pt/C. The lifted HOMO energy level and lowered d band center of Pt/C@PANI compared with Pt/C were beneficial to the electron transfer between Pt/C@PANI and 02 due to the reduced gap between the Pt/C@PANI HOMO and the oxygen LUMO, and the desorption of intermediate species on the surface of the catalysts and releasing fresh catalytic sites for the subsequent reaction.
出处
《中国科学：化学》
CAS
CSCD
北大核心
2013年第11期1566-1571,共6页
SCIENTIA SINICA Chimica
基金
国家自然科学基金(20936008
51072239和21176327)
中央高校基础研究基金(CDJZR12228802)资助
关键词
燃料电池
密度泛函
氧还原
铂
聚苯胺
fuel cell, density functional, oxygen reduction, platinum, polyaniline
